Modified c3 corvette

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We Can't Stop Staring At These Perfectly Modified C3 Corvettes

Chevrolet is well-known for its incredible vehicles. From its very inception, the company produced vehicles that were directly rivaling the most popular Ford automobiles. As time went by, Chevrolet cemented its reputation at home and expanded its operations abroad. Today, the names Camaro and Corvette are synonymous with sportiness and exclusivity.

RELATED: 10 Corvettes Every Enthusiast Wants To Drive

The Corvette C3 is among the most iconic Corvettes ever made. When ranking the best Corvettes ever made, the C3 definitely comes in the top three. Though some of its engines were simply disappointing, the technology and widespread tuning available today can turn this great classic into an absolute monster.

10 Black Widow

The Corvette C3 is the third generation Corvette and the second time Chevrolet branded its high-end muscle car the Stingray. Produced between 1968 and 1982, the C3 went through numerous changes, including a drastic diminution of its power output. That being said, C3s produced before the Malaise Era were quite impressive.

RELATED: We Can't Stop Staring At These Modified Classic Corvettes

This C3 is among the greatest classic Corvette restomods that gearheads have ever seen. First of all, the car does not look overly modified. Second, the insane 7.0-liter LS7 V8 is sitting under the hood, and thanks to its 505 hp, this old school Corvette can easily keep up with newer C8s.

9 Candy Paint

Corvettes are cool—there is no denying that. However, in sunny states, the must-have is a Corvette convertible. Imagine driving down Pacific Coast Highway in a sick old school Corvette. This is the definition of success. However, it is always possible to enhance that amazing feeling by giving a classic Corvette some aftermarket parts.

This Corvette C3 convertible is a true marvel. The car was given some truly impressive rims. The paint job sure is mesmerizing, but it is nothing compared to the powerplant that is found in the engine bay. The original 327ci V8 was replaced by a much bigger 427ci engine that produces 430 hp and 444 lb-ft of torque.

8 Silver Bullet

The very first year the C3 was produced, the car was a huge upgrade from the previous edition. The newer Stingray was powered at best with the infamous L88 powerplant. Rated at 430 hp, the '68-'69 Corvette C3 was nothing to be looked down upon. However, if the engine bay could accommodate the L88, it could also welcome more modern engines.

This C3 is unlike most C3s. The car was fitted with a 7.0-liter LS7 engine tuned to produce 700 hp. The engine is also coupled with a six-speed transmission and a brand-new chassis. This pro-tourer was featured at SEMA a couple of years back. It is fair to say that this C3 deserved to be shown to the public.

7 Simplicity

It is fair to say that the C3 is a beautifully designed vehicle. Like most Corvettes, the C3 was diligently engineered by the best Chevrolet employees. As a result, the car came out looking absolutely stunning. On top of being incredibly beautiful, the C3 was originally capable of handling like a race car.

Unfortunately, the background information on this Corvette C3 is unavailable. However, it is fair to assume that the car was given some intelligently chosen aftermarket parts. When looking at the rims and cowl hood, it is safe to say this C3 packs a lot more punch than most stock C3s.

6 Rambo

The best part about oldies is the fact that they can be enhanced in order to look even better. Thanks to the skilled tuners and technology available today, it is possible to turn a regular Corvette into a demonic beast. Not only does the car look like a million bucks, it can also perform really well on the track.

This pro-touring C3 Corvette widebody is nicknamed "Rambo". It's highly unlikely that anything named Rambo is weak. This C3 is the equivalent of Sylvester Stallone wielding an M60E3 without any issues. The original 5.7-liter LT1 V8 found under the hood was modified to produce 500 hp. This is a very decent amount of power for a somewhat amateur-made pro-touring car.

5 Canary

It is often wrongly believed that modifying a classic car involves adding a myriad of stickers and an oversized wing. This could not be further away from the truth. There are a plethora of builds out there that look extremely simplistic despite the amount of work that was put into the car.

RELATED: 10 Legendary Corvettes We'd Love To Drive

Yellow may not be everybody's color of choice, however, this bee-like C3 pulls it off quite nicely. The original engine was swiftly replaced by a ProCharger D1 supercharged 408 ci V8 that produces 750 hp and 685 lb-ft of torque. This is one fast Corvette C3.

4 Wrapped

Over the last decade or so, intricate paint jobs sort of fell out of style. As wraps became more popular thanks to their modularity, paint jobs costing thousands of dollars were simply forgotten. Wraps are great despite the fact that several car owners often go with the most laughable wraps made available.

This wrapped C3 is the sort of classic Corvette restomod car fans prefer to drive over the new C8. This C3 is not overly powered like some restomod C3s out there. However, as far as aesthetics are concerned, this C3 received what is best out there. The Forgeline rims combined with the matte blue wrap are simply breathtaking.

3 Manta

When the restomod trend really picked up some wind, most people with a decrepit oldie started dreaming about giving their once beloved car a second youth. Though not everybody is financially capable of turning a barn find into a 600 hp car, it is possible to generate some serious profit depending on what is sitting in the garage.

This C3 is worth quite a bunch of cash. After being completely restomodded, it was given a second life. The sluggish original engine was replaced by a 6.2-liter V8 that produces 437 hp and 424 lb-ft of torque. That is not too shabby. Built by Hardcore Engine Builders, this C3 will certainly turn heads.

2 Mamba

There are times when tuners modify their cars following trends that are not really popular among domestic gearheads. For example, most car enthusiasts would lose their minds if they stumbled across a Shelby GT500 with negative camber, a huge wing, and a manga vinyl wrap.

RELATED: How To Modify A Corvette The Proper Way

The build story behind this green Mamba Corvette is quite insane. This wild beast was modified in order to be the best restomod pro-tourer out there. The list of modifications is way too long to enumerate each and every single one of them. The 427ci V8 was tossed out in order to make room for a much more potent LS7. With a power output of 650 hp, this green monster will for sure be a show-stopper.

1 Insanity

Imagine you find a C3 on Craigslist for a very decent price, and decide to modify it using the $100,000 you just happened to have lying around somewhere. Chances are you'll pull up to car meets in a beautiful Corvette C3 similar to this midnight blue pro-tourer.

A pro-tourer does not have to look like a complete race car. It can also look like a highly-modified daily driver. This C3 is the perfect example. The 427ci was replaced by an LS engine, however, the information relating to the engine's power output is not available. This C3 is nonetheless gorgeous and ready to tear up its rivals.

NEXT: We Love These 10 Modified C5 Corvettes

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About The Author
Max Veron (293 Articles Published)

Max Veron is an avid fan of anything equipped with a powerful engine. Spending time between Southeast Asia, Europe and the US, Max is travel bug with a great taste for cars.

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Sours: https://www.hotcars.com/perfectly-modified-c3-corvettes/

C3 Corvettes Engine Modification Guide

You have an enormous number of options for engines and engine modifications. Most Sharks are equipped with the small-block Chevy, and an almost infinite number of heads, cams, intake, exhaust, ignition, rotating assembly, and other performance part are available. You can build anything from a mildly modified street engine to a race engine. If you have or want to install a Chevy big-block, the number of modifications is nearly as extensive and diverse.

 


This Tech Tip is From the Full Book, CORVETTE C3 1968-1982: HOW TO BUILD AND MODIFY. For a comprehensive guide on this entire subject you can visit this link:
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I spent many of my early years pulling cylinder heads and replacing camshafts on a long weekend or two, looking for more power. Sometimes the correct decision was made in haste, and other times a decision was made in haste and a crucial step was missed. Proper and methodical planning is key to any engine project and most automotive projects. You need to develop a clear goal and work back from that to the beginning of the project so all the engine parts are compatible and complementary. But you also need to plan out each crucial step along the way so every step is completed correctly and professionally. Not having a clear goal always costs additional time and money; not evaluating the engine health can set you up for a major disappointment.

 

This 1977 Shark received a GM crate engine with many custom components. The K&N air filter resides atop the Professional Products 52007 dual-plane Vortec intake manifold. The use of the small-cap MSD distributor with 6AL multi-spark discharge box frees up some space at the back of the engine for the wiring and wiper motor. The inline fuel gauge was placed under the hood to keep fuel out of the cockpit. You should see 3 to 4 pounds of pressure while idling. If the pressure decreases when the throttle is increased, there is a restriction on the supply side of the fuel pump.

This 1977 Shark received a GM crate engine with many custom components. The K&N air filter resides atop the Professional Products 52007 dual-plane Vortec intake manifold. The use of the small-cap MSD distributor with 6AL multi-spark discharge box frees up some space at the back of the engine for the wiring and wiper motor. The inline fuel gauge was placed under the hood to keep fuel out of the cockpit. You should see 3 to 4 pounds of pressure while idling. If the pressure decreases when the throttle is increased, there is a restriction on the supply side of the fuel pump.


 

Your current engine should go through an evaluation and inspection process to determine what direction to proceed. Your engine may be in questionable health: adding performance pieces could add the death blow to an already worn-out engine. Mileage is usually a factor to take into account when engine health is considered. When the early Shark odometers turned over at 100,000, often the engine was in need of a rebuild. You need to perform an engine compression and/or leak-down test to determine whether the engine needs to be rebuilt. Cylinder compression is an important measurement of overall engine health. Leak-down testing is the best way to check for excessive crankcase pressure (blow-by, as it is often called), valve sealing, and head gasket integrity. As piston rings and cylinder walls wear, combustion gases are forced into the crankcase, creating the excess pressure. A good indicator of worn rings is seeing a steady puff of smoke belching from the valve cover’s PCV valve grommet.

Observing the oil pressure, especially once the engine coolant temperature reaches more than 180 degrees, is an important step in determining the engine’s rotating components’ health. With fresh oil, you should see 15 to 30 psi at idle with the pressure rising to a minimum of 50 to 60 at high RPM. On an extremely hot day, oil pressure may run as low as 10 to 15 psi at idle, and that is normal. However, the pressure must rise as RPM increases. Low steady oil pressure in the 25- to 30-psi range at high RPM is a warning. It is a clear indication of worn internal rotating components. Big-block engines have different oil pressure requirements from idle to wide-open throttle (WOT). Your big-block should idle with at least 30 psi; 35 to 40 is preferred for performance-use engines. Once the throttle is opened, you should see a minimum of 60 to 75 psi as you near the engine’s redline.

 

The light blue fog around this slightly tired small-block’s PCV valve grommet is not too concerning, as engines wear, piston ring blow-by increases. Severely worn engines have a constant puff of very easily seen blue smoke: engine overhaul is necessary at that point.

The light blue fog around this slightly tired small-block’s PCV valve grommet is not too concerning, as engines wear, piston ring blow-by increases. Severely worn engines have a constant puff of very easily seen blue smoke: engine overhaul is necessary at that point.

 

Remove the spark plugs for the compression and leakdown testing. Be careful with the spark plugs as you remove them. Use a Sharpie to write the cylinder number on the insulator as you remove them. As you proceed with the evaluation, the plugs provide clues to help determine the engine’s health. For the best results, the throttle should be held wide open while the engine is turned over five to six full revolutions per cylinder. This maintains testing uniformity. Place a screwdriver in the throttle linkage so the butterflies are held wide open. This ensures that the throttle position is the same for every bore and that the compression and/or leak-down test is accurate. A black, oily deposit on the spark plugs is an indication that the rings may be worn excessively. Record the compression readings. Any low cylinder readings on the compression test are confirmed during the leak-down test. You are looking for a balanced compression test with the cylinders within 10 percent of each other.

Remove the spark plugs for the compression and leakdown testing. Be careful with the spark plugs as you remove them. Use a Sharpie to write the cylinder number on the insulator as you remove them. As you proceed with the evaluation, the plugs provide clues to help determine the engine’s health. For the best results, the throttle should be held wide open while the engine is turned over five to six full revolutions per cylinder. This maintains testing uniformity. Place a screwdriver in the throttle linkage so the butterflies are held wide open. This ensures that the throttle position is the same for every bore and that the compression and/or leak-down test is accurate. A black, oily deposit on the spark plugs is an indication that the rings may be worn excessively. Record the compression readings. Any low cylinder readings on the compression test are confirmed during the leak-down test. You are looking for a balanced compression test with the cylinders within 10 percent of each other.

 

Use a leak-down tester for the ultimate engine cylinder performance test. Thread the leak-down tester into each cylinder. The gauge on the right side of the tester informs you that this cylinder has 4 percent leakage. New engines are in the 2 to 8 percent leakage range; heavily worn engines are above 15 percent. The leak-down test also indicates cylinder balance. If there is more than a 10 percent difference in any cylinder, rough engine performance can be expected. If you find that the leakage is severe enough to be audible, check for escaping air out the intake or exhaust. Also look at the radiator filler for possible bubbles in the coolant from a blown head gasket. Be careful when connecting the air supply; if the crankshaft rotates your hand or other body part could possibly be caught in a pinch point.

Use a leak-down tester for the ultimate engine cylinder performance test. Thread the leak-down tester into each cylinder. The gauge on the right side of the tester informs you that this cylinder has 4 percent leakage. New engines are in the 2 to 8 percent leakage range; heavily worn engines are above 15 percent. The leak-down test also indicates cylinder balance. If there is more than a 10 percent difference in any cylinder, rough engine performance can be expected. If you find that the leakage is severe enough to be audible, check for escaping air out the intake or exhaust. Also look at the radiator filler for possible bubbles in the coolant from a blown head gasket. Be careful when connecting the air supply; if the crankshaft rotates your hand or other body part could possibly be caught in a pinch point.

 

Inspection and Testing

A good procedure to determine engine health begins with a compression test to see if there are any variations in cylinder pressure. Variations in pressure could indicate leaking valves, blown head gaskets, or bent connecting rods. As you proceed to the leak-down test, you can determine if the low pressure is due to internal leakage or short connecting rods. When connecting rods bend, rod length gets shorter; consequently, cylinder volume is added and compression ratio drops. Make a note of the cylinders with lower pressure, as it is imperative to determine which cylinder is out of factory spec.

In some cases, something as simple as incorrect valve adjustment causes the problem. Removing the rocker arms during the leak-down test verifies the misadjusted valves if you record the findings from each test. Your spark plugs also indicate a worn engine if they have black crusty deposits. Black insulators warn you that the engine was running too rich, possibly washing the oil off the cylinders and causing excessive piston ring wear.

Parts Compatibility

Now that your engine’s health has been determined, you should consider its reliability factor as parts are chosen. Factory engine rotating components are typically adequate for up to 400 hp. If horsepower rises above 450, it’s tough on the bottom end, so don’t expect original-equipment rotating components to live long. As horsepower increases, reliability decreases. Now it’s time to make some choices.

Cylinder heads, camshaft, and compression largely determine the final power output of any given engine. At least 95 percent of an engine’s power is determined by the Big Three—this has been the rule in the past, and it will hold true in the future.

Essentially, engines are air pumps that perform best when the air entering and exiting the engine occurs as rapidly as possible. Installing high-flow aftermarket cylinder heads while using the factory intake and exhaust manifolds limits the cylinder head’s airflow design advantages. Installing a high-flow intake and exhaust with factory cylinder heads also produces minimal power gains. In addition, using the factory camshaft with new aftermarket performance pieces limits power gains as well. It should be evident that you need to select compatible and complementary components because the engine works as a system and the function and operation of one component directly affects another. You need to figure out the best intake manifold, cylinder heads, and camshaft for your application. Changing multiple components is another way to go until you hit something that “works” but that is costly and time consuming. I simply do not have the space to provide all the relevant options and combinations of engine parts for a wide range of C3 powerplants. How to Build Max-Performance Chevy Small-Blocks on a Budget by David Vizard and How to Build Big-Inch Chevy Small-Blocks by Graham Hansen are two excellent resources. They go into detail on building max-performance and stroker small-block Chevy engines.

Virtual Dyno Testing

You can back up the component manufacturers’ recommendations by using testing software, such as Virtual Engine 2000, which has proven to be very accurate. This product lets you input pertinent data, and then a virtual dynamometer pull is performed, showing you what power gain or loss the new component has contributed. The dynamometer software lets you check all the performance engine components you install, including the intake manifold, camshaft, exhaust system, and cylinder heads.

Desktop Dyno Engine Simulation is another virtual resource to ensure the correct performance parts combination. The same premise applies: input your engine data and test your performance parts choices. One advantage is that the Desktop Dyno software allows nitrous-oxide testing; at the other end of the spectrum fuel mileage can also be determined.

 

This Virtual Engine Dyno software makes plenty of good sense to avoid extra work and wasting your hard-earned dollars. You can record each parts change and archive the dynamometer run until you fi nd what works best. This really works well and is very close to the actual engine torque and horsepower output.

This Virtual Engine Dyno software makes plenty of good sense to avoid extra work and wasting your hard-earned dollars. You can record each parts change and archive the dynamometer run until you fi nd what works best. This really works well and is very close to the actual engine torque and horsepower output.


 

You can start component testing before the first wrench is turned. You need to know some very specific engine information for the most accurate end results. Keep in mind that guessing and inputting incorrect data can result in huge disappointments, or a major surprise with excellent power gains. Engine bore size, stroke, and combustion chamber volume can be found in factory service manuals after verifying your engine’s build codes. After you have taken some time to get acquainted with the software, figuring out the correct pieces is easy.

 

Be sure to input the correct information. You must be extra careful so you have better accuracy on the dynamometer run. Compression means a lot in the final power output numbers, and that is the toughest information to obtain. Valve clearance cut-outs affect piston dome volume, so you need to precisely calculate the clearance spec. Aftermarket piston manufacturers provide precise numbers; stock flat-top GM pistons are -9.2 cc if they have four valve clearance cut-outs.

Be sure to input the correct information. You must be extra careful so you have better accuracy on the dynamometer run. Compression means a lot in the final power output numbers, and that is the toughest information to obtain. Valve clearance cut-outs affect piston dome volume, so you need to precisely calculate the clearance spec. Aftermarket piston manufacturers provide precise numbers; stock flat-top GM pistons are -9.2 cc if they have four valve clearance cut-outs.

 

Intake Manifolds

An enthusiast often first installs an aftermarket aluminum intake manifold. Intake manifolds are typically single- or dual-plane design. Single-plane intakes typically have shorter, higher-angled runners (intake tracts) making the power band come in later, allowing higher RPM capabilities. Dual-plane intakes have longer and typically smaller-diameter intake runners, which enhance torque as they prevent reversion of incoming air while restricting high-RPM airflow.

If you want to make good torque at low RPM, dual-plane intakes are the ticket. If high-RPM horsepower is your game, select a single-plane intake manifold.

 



 

The tough part of making an intake manifold decision is all the factors to consider. Larger-cubic-inch engines can provide plenty of torque with single-plane intakes, depending on many factors. Engine compression and camshaft selection, for instance, affect the torque output and, more important, when peak torque occurs. The smart plan is to carefully examine the possibilities and heed the manufacturer’s recommendations on the combinations that work.

The trick is balancing optimum intake performance with available underhood clearance when using factory hoods. In my experience, Shark owners rarely opt to install an aftermarket hood because they want to retain the factory look. Few single-plane intake manifolds fit under a stock hood. Typically, dualplane intakes sit much lower in the engine valley and allow the carb to fit under the stock hood. You need to select the entire intake package to clear the stock hood or you need to select an aftermarket hood that’s compatible with your intake package. That means the intake manifold, air cleaner, and yes, even the wing nut and air cleaner stud need to fit under the hood.

 

Organization is the key, with an undisturbed area to store the pieces as they are removed. I prefer a mobile cart to set the removed pieces on. Next, I evaluate the pieces to decide whether they require cleaning or replacing. I make it a policy that any piece that will be replaced is removed from the cart when the new one arrives, and only the required pieces for assembly are on the cart. When the job is completed, there should be no pieces left on the cart. If there are, I know that something was left out. The valvetrain tray is a good organizational tool. If you plan to reuse any of the pieces, they should stay in the same location they have worn into.

Organization is the key, with an undisturbed area to store the pieces as they are removed. I prefer a mobile cart to set the removed pieces on. Next, I evaluate the pieces to decide whether they require cleaning or replacing. I make it a policy that any piece that will be replaced is removed from the cart when the new one arrives, and only the required pieces for assembly are on the cart. When the job is completed, there should be no pieces left on the cart. If there are, I know that something was left out. The valvetrain tray is a good organizational tool. If you plan to reuse any of the pieces, they should stay in the same location they have worn into. 


 

How to Measure Hood Clearance

Many GM and aftermarket intake manifolds are available. Each Shark is individual as body support cushions wear and hood clearances get tighter. The front-end bodywork often sags over time, which can be seen at the upper fender to door clearances. The gaps widen and the hood becomes closer to the air cleaner. You need to ensure that there is enough clearance between the air cleaner and the hood.

 

This is the telltale sign that the air cleaner is right there, just slightly touching the hood on deceleration. Remember that the engine does move around, and you need at least 1/2-inch wiggle room to keep the hood from getting chewed up. The center of the hood is raised slightly, so the air cleaner wing nut and stud usually have enough room if the circumference of the air cleaner top cover misses the hood. Never just drop the hood until you know that there is adequate clearance. Lower the hood slowly and then push it down to lock it.

This is the telltale sign that the air cleaner is right there, just slightly touching the hood on deceleration. Remember that the engine does move around, and you need at least 1/2-inch wiggle room to keep the hood from getting chewed up. The center of the hood is raised slightly, so the air cleaner wing nut and stud usually have enough room if the circumference of the air cleaner top cover misses the hood. Never just drop the hood until you know that there is adequate clearance. Lower the hood slowly and then push it down to lock it.


 
 installed this slightly raised dual-plane intake on Project Shark Attack with a Holley throttle body fuel-injection system. I prefer to use Fel-Pro steel laminate core intake gaskets for easy trimming of the port openings and long-term sealing. Intake manifolds squirm around on the cylinder heads as they heat and cool. In the long term this tears away at composite gaskets. The 383-ci engine had more than 400 ft-lbs of torque and made 403 hp at 5,500 rpm: not too bad for an all-around play toy

installed this slightly raised dual-plane intake on Project Shark Attack with a Holley throttle body fuel-injection system. I prefer to use Fel-Pro steel laminate core intake gaskets for easy trimming of the port openings and long-term sealing. Intake manifolds squirm around on the cylinder heads as they heat and cool. In the long term this tears away at composite gaskets. The 383-ci engine had more than 400 ft-lbs of torque and made 403 hp at 5,500 rpm: not too bad for an all-around play toy.


 

The only way to do that is to measure from the engine block intake manifold sealing surface to the hood. This determines whether there is adequate clearance. Aftermarket intake manifold manufacturers such as Weiand, Edelbrock, and Professional Products have fitment measurements on their websites, including how-to-measure instructions.

Once hood clearance is determined and a manifold is purchased, always check again for clearance before dropping the hood for the first time.

Replacing the Intake

The replacement of an intake manifold on the big- or small-block Chevy engine is one of the easiest mods to perform. Keeping things clean is the key; preparation and then torquing the intake bolts in sequence ensures a tight seal with no oil leaks.

Intake Manifold Installation

Step 1: Match Intake Ports on Cylinder Heads

 

SA247_FULLBOOK_C3Corvette_Page_012_Image_0003I am beginning to port- or gasket-match this intake to a set of Patriot cylinder heads. This engine will be run at 6,500 rpm and above often. The port on the right is quite a bit smaller and would be fine for a low-RPM high-torque engine. If you plan on using outof-the-box cylinder heads, one of the main concerns is to make sure the intake port is smaller than the cylinder head port to avoid airflow disturbance as the intake air and fuel enter the cylinder head. If the cylinder head ports are larger than the intake port, there is no need to do any machining if you plan on keeping the RPM below 5,500. Unless you just have to have matching ports, you don’t feel any performance gain.

Step 2: Prep for Gasket Install

SA247_FULLBOOK_C3Corvette_Page_012_Image_0004I am prepping the cylinder head and engine block end surfaces for gasket installation. As you see, I have stuffed each port with paper towels to keep debris out of the engine. Previously the same blue towels were lying in the valley area to collect debris. If any debris falls into the lifter valley, take some time and remove it to avoid filling the oil pump pick-up tube with junk. I use naphtha, brake cleaner, or alcohol to wipe down all surfaces before placing the gaskets on the engine.

Step 3: Seal Engine Top End

SA247_FULLBOOK_C3Corvette_Page_013_Image_0001Hot oil-resistant silicone sealer is used at the front and back of the intake manifold for the best sealing. Before we put the gaskets in place on this Racing Head Service castiron Vortec cylinder head, a dab of silicone is placed in the corner of the cylinder head and engine block below the gasket. Then silicone sealer is applied in a 3/16- to 1/4-inch bead ending approximately 1/4 inch up the intake gasket at the corners to prevent oil leakage. Not only does oil leak out, unfiltered air in the engine compartment can be drawn into the engine.

Step 4: Torque Intake Manifold

SA247_FULLBOOK_C3Corvette_Page_013_Image_0002Proper sealing and torquing of the intake manifold are important if you want to avoid intake leaks and prevent distorting or breaking your aluminum intake. This Weiand intake on an early small-block requires bolt sealing to prevent oil from wicking up the bolt threads. I also apply Never-Seez to the outer four bolts to prevent rust or corrosion from forming in the threads if the intake gaskets weep coolant over time. Torque the intake manifold to the supplier’s recommendation, which is 35 to 40 ft-lbs. Take the extra time and read the instructions. Tighten the bolts in sequence and torque the intake bolts to their specs. Tightening sequence is equally important to avoid a cracked or broken intake flange. I use the tightening sequence for a preliminary hand tightening to seat the manifold, then go back and do the final torque. For the most part the tightening sequence starts at the center and works outward, alternating across the intake.

Cylinder Heads

Consider the following when selecting heads. Cast-iron cylinder heads are capable of making plenty of power for many reasons, including excellent thermal efficiency. Aluminum cylinder heads dissipate heat quicker, which drops combustion chamber heat, lowering their thermal efficiency. Castiron cylinder heads are much harder to port match and maximize flow with the denser material; because of this, few people use them as performance pieces. Aluminum cylinder heads are lighter weight, and the easy-to-modify intake tracts have made them very popular. Always consider the cylinder head’s combustion chamber size and piston configuration that affect your engine’s compression ratio. Higher compression ratios make more power and require higher-octane fuels.

Racing Head Service has a couple of cast-iron cylinder head options. The 64-cc combustion chamber yields a 9.90 to 10.10:1 compression ratio, depending on the pistonto-deck height. Pistons can also be purchased with two or four valve reliefs, which affects compression ratio. When your compression ratio approaches 10.0, you must use premium pump gas and pay close attention to ignition timing. I keep total ignition timing at 36 degrees or less to prevent pre-detonation (spark knock).

Racing Head Service has a couple of cast-iron cylinder head options. The 64-cc combustion chamber yields a 9.90 to 10.10:1 compression ratio, depending on the pistonto-deck height. Pistons can also be purchased with two or four valve reliefs, which affects compression ratio. When your compression ratio approaches 10.0, you must use premium pump gas and pay close attention to ignition timing. I keep total ignition timing at 36 degrees or less to prevent pre-detonation (spark knock).


 

Small-Block Cylinder Head

Original-equipment GM small-block heads have angled valves relative to the block deck. If you look at the top of the cylinder block, the valves are angled 23 degrees inward at the top toward the intake manifold area. Race-bred smallblock cylinder heads have 18-degree valve angles, and the intake ports are not raised as high. This allows a smoother transition for incoming air into the cylinder head. The 18-degree heads require many extra pieces and are impractical when using a stock lower end with a cylinder head/cam change. In this section I only discuss the 23-degree version.

The 1968–1974 OEM Shark smallblock (and big-block cylinder heads, by the way) has cast-in valveseats and valveguides. When unleaded fuels were introduced in 1975, valveseat temperatures were elevated, requiring tougher materials to withstand the heat. From 1975 on, General Motors installed replaceable hardened seats in its cylinder heads to handle the unleaded fuels.If you choose a set of pre-1975 GM cylinder heads for your project, expect to spend extra on machining and installation of hardened seats.

Excessive valveguide wear has been an issue on 1968–1982 GM heads. As the guide wears, it must be machined out and an aftermarket valveguide installed. Knurling is a less expensive alternative machine operation performed to tighten the valve in a worn valveguide. The cost of knurling is considerably less than replacing 16 valveguides. This is a temporary fix at best and not recommended for long-term performance use.

Check with your local machine shop about the cost; in the majority of cases, modifying original cylinder heads comes close to the cost of purchasing a set of aftermarket or GM performance cylinder heads. Your pre-1975 cylinder heads still have the same airflow rates and need a lot of work grinding on cast iron to achieve any dramatic results.

GM’s small-block performance aluminum cylinder head with D-shaped exhaust port is in plentiful supply and can be found on 1986 to late-1991 Corvette L-98 engines. General Motors designed the L-98 aluminum cylinder heads for the Tuned Port Induction (TPI) engine that made high torque at low RPM. The Corvette’s L-98 engine was breathing hard at 4,500 rpm because of the intake design, so the heads do not flow big numbers at high RPM. L-98 cylinder heads are good for 400 hp with plenty of torque in excess of 400 ft-lbs at or below 5,000 rpm. The L-98 cylinder head is relatively inexpensive and can be readily found at swap meets, so this makes them a deal unless you’re after high-RPM horsepower. To make high-RPM horsepower, they require plenty of porting work.

There is also a concern with the L-98 head’s limited valve-opening clearances, requiring extra pieces to make them compatible with high-lift camshafts. It makes sense to run the budget numbers before buying a used set of L-98 heads and then prepping them for high RPM with a highlift camshaft.

General Motors made a really great-flowing OEM cast-iron cylinder head for use on 1996–1999 truck applications. The same Vortec cylinder heads were available from GM Performance Parts (now Chevrolet Performance) as an aftermarket replacement part. The Vortec heads had an improved combustion chamber, promoting better flow with a slight change in spark plug placement for better combustion. The heads are easy to spot because of their intake manifold retention bolt configuration. All Gen I non-Vortec cylinder heads use 12 bolts at a 90-degree angle to retain the intake to the cylinder heads. When the Vortec cylinder heads were introduced in 1996, 8 bolts at a 72-degree angle fastened the intake manifold onto the heads.

As you can imagine, when using GM Vortec heads the intake manifold must be replaced. The Vortec heads flow much better at low valve lift numbers than the late-1986–1991 Corvette L-98s, allowing horsepower to approach 480. General Motors redesigned the Vortec cast-iron head with taller, narrower intake runners and dual-bolt patterns with two port sizes (PN 25534421 for the small port and PN 25534431 for the large port). If you don’t mind a little extra weight, the Vortec head saves you a few dollars with airflow numbers approaching CNC-ported aluminum heads.

The aluminum L-98 cylinder head found on the 1987–1991 Corvette provides exceptional torque for street performance below 5,500 rpm. These are widely available and reasonably priced. They come with screw-in rocker studs, so they can handle higher revs and help provide accurate valve actuation. Porting does help and the D-shaped exhaust ports help flow. One thing to watch for is valve lift: .500 is the maximum lift for the camshaft, or valvespring retainers begin hitting the valveguides.

The aluminum L-98 cylinder head found on the 1987–1991 Corvette provides exceptional torque for street performance below 5,500 rpm. These are widely available and reasonably priced. They come with screw-in rocker studs, so they can handle higher revs and help provide accurate valve actuation. Porting does help and the D-shaped exhaust ports help flow. One thing to watch for is valve lift: .500 is the maximum lift for the camshaft, or valvespring retainers begin hitting the valveguides.

 

This is one of the best values on a healthy engine. These 305-cc intake runner cylinder heads were installed on a 427-ci engine for my 1969 Shark. The 117-cc combustion chamber and factory 435-hp pistons had the compression at 10.0:1. The first dyno test was with a stock set of iron big-block heads and OEM 435 flat-tappet camshaft. I was pleased with the 460 hp at 6,000-rpm pull. The next pull was after changing the stock big-block rectangular heads to these AFR replacements: an astonishing 540 hp at 6,500 was recorded.

This is one of the best values on a healthy engine. These 305-cc intake runner cylinder heads were installed on a 427-ci engine for my 1969 Shark. The 117-cc combustion chamber and factory 435-hp pistons had the compression at 10.0:1. The first dyno test was with a stock set of iron big-block heads and OEM 435 flat-tappet camshaft. I was pleased with the 460 hp at 6,000-rpm pull. The next pull was after changing the stock big-block rectangular heads to these AFR replacements: an astonishing 540 hp at 6,500 was recorded.

 

Big-Block Cylinder Head

GM big-block cylinder heads came in a large number of configurations on the early Shark, including oval-intake port for standard-performance and rectangular intake port for high-performance versions. Open and closed combustion chamber versions were also intermingled among oval- and rectangular-port cylinder heads. Oval-port intake runner volume is less than that of a rectangular port. Oval-port heads produce better low-speed torque output while hindering high-RPM power. Closed-chamber cylinder heads have less combustion chamber volume, which increases the compression ratio. Open-chamber big-block cylinder heads have better airflow characteristics with unobstructed valves.

The GM rectangular big-block cylinder head was offered in various aluminum versions. These special high-performance aluminum cylinder heads made it into limited production on Shark Corvettes with RPO L-89-optioned 427-ci engines. Casting integrity plagued the early bigblock aluminum heads, so few were used in production or sold over the counter. These heads are rare pieces and best suited for high-end restorations.

You should consider buying a set of aftermarket high-performance heads that’s suited to your performance package rather than using limited-production Shark cast-iron big-block cylinder heads in a high-performance application. Let someone use the hard-to-find early bigblock heads on a numbers-matching restoration.

 



 

Aftermarket Cylinder Head

Most aftermarket cylinder heads are aluminum castings. However, cast-iron cylinder head companies, such as Racing Head Service, offer some excellentflowing iron heads that save you a few bucks. Although cast-iron heads are heavier than aluminum heads, the cost savings may steer you that way. Ultimately, a Shark’s front-to-rear weight balance is most important for handling. The majority of us cannot use the available power, and anything that improves handling makes better sense.

In most cases aftermarket cylinder heads have larger valves than stock heads to maximize airflow. They raise the intake port at the manifold area and modify the intake runner volume, maximizing the airflow into the intake valve area. Combustion chamber design is optimized to swirl the incoming air and fuel mixture for the best homogenous flow into the engine’s cylinders.

Spark plug placement is also optimized for the best possible flame travel during the fuel’s ignition process.

Valveseat science has also grown tremendously, with five-angle seat machining replacing the three-angle seat formation that was used for many years.

Intake runner volume is a hot topic in the high-performance community. As with a small-diameter straw, it takes more effort to draw through it than with a larger-diameter straw. Having the highest flow numbers does not necessarily mean the best overall power combination. Low intake runner volume helps low-RPM torque by increasing the velocity of the incoming air into the cylinder. On the big end, though, it can hurt high-RPM power as a restriction.

Choosing the correct intake runner volume requires camshaft, intake, and vehicle usage info. A correctly set up intake, cylinder head, and camshaft features a single-plane intake for up to 7,000 rpm use, and a long-duration camshaft with 210-cc intake runner volume cylinder heads on a 350- to 383-ci engine. The opposite end of the spectrum is a dualplane intake for a maximum of 5,500 rpm, and a mild camshaft with 180-cc intake runner cylinder heads maximizing low-RPM torque for 350-ci engines.

A few manufacturers of ready-tobolt-on performance cylinder heads make your task easier when it comes time to find the maximum horsepower. One of the top performers is Airflow Research (AFR). Great-flowing small- and big-block cylinder heads are what AFR is about, through many years of flow testing and tweaking for the most available power. Patriot Performance cylinder heads are another choice at excellent prices for the performance gain. Edelbrock has a number of options for both big- and small-block engines. They all have good products that provide out-of-the-box performance gains. The smart move is to contact them and see what they have to offer, then use their specifications for a run on your Desktop Dyno or Virtual Engine 2000 software. Don’t forget the intake manifold/hood clearance restrictions; that excellent-flowing cylinder head may not work as designed if the intake manifold is prohibiting airflow.

Cylinder Head Installation

The installation of heads typically takes a few days. Cleaning alone can take three to four hours when done properly but time spent cleaning makes the difference in keeping your engine alive for the most possible miles. Cylinder head gaskets affect sealing, compression ratio, and possibly valve-to-piston clearance. You need to pay particular attention to any recommendations the manufacturer provides.

Cylinder Head Installation

Step 1: Prep Block for Head Installation

SA247_FULLBOOK_C3Corvette_Page_016_Image_0001This original 1969 Shark 350-hp engine had good compression and minimal leak-down, making it a good candidate to replace its original cast-in valveseat heads for a set of new, high-flow cylinder heads. This cleaning step is often missed during the installation phase. Thirty-two of the 34 head bolt threads are subjected to coolant, which prevents a proper tightening. The grit between the threads makes it feel as if you torqued the bolts to 65 ft-lbs, but in reality the threads are tight, not the cylinder heads. A 7/16- 14 thread tap is used for the cleanout. Be careful when cleaning the top row of bolts; the tap can bottom out and break.

Step 2: Verify Trueness of Machined Surfaces

SA247_FULLBOOK_C3Corvette_Page_016_Image_0002Central Tools provides precision measuring and testing tools such as this straightedge being used to check for cylinder head damage. The first step in checking the cylinder head for any distortion is to clean any carbon and gasket material from the surfaces. I left half of the cylinder head sealing surfaces as they came off the engine to show that there is quite a buildup of material that affects the testing procedure. The most common areas of distortion are between the cylinders. Place the straightedge lengthwise across the head surface. Insert a feeler gauge between the straightedge and the surface of the head. The .002-inch feeler gauge is being used to see if this cylinder head requires machining. The engine block should also be checked for any discrepancies, or you will pay the price in repeated head gasket failures.

Step 3: Prep Engine Block

SA247_FULLBOOK_C3Corvette_Page_016_Image_0003Fairly new cotton T-shirt material works well for wiping down the block surfaces before gasket installation. But you need to be sure the rag is lintless, because you don’t want the fiber of the rag to get inside the engine and cause damage or potential failure. Coarse rags may leave behind lint on a recently machined cylinder head deck. Here, naphtha or brake cleaner removes any grease or oil left behind from piston installation. Any oil left behind prevents gasket material sealing, creating plenty of extra work when you find that the heads have to come off for another set of gaskets.

Step 4: Install Cylinder Heads

SA247_FULLBOOK_C3Corvette_Page_016_Image_0004The task seems simple enough: Pick up the cylinder head and set it on the engine block. Aluminum heads make the job easier, but they, like cast-iron cylinder heads, can cut the head gasket or put a serious ding in it that will cause grief later. Try to set the head level and on the alignment pins, moving it around until it seats on the pins. If a sharp edge cuts into the gasket you could be doing this all over again. Combustion leaks can occur: once they do, they can do severe damage to the engine block and/or cylinder heads.

 

Step 5: Torque Cylinder Heads

SA247_FULLBOOK_C3Corvette_Page_017_Image_0001This is serious stuff here, especially if you plan on putting some extra squeeze in the cylinder with nitrous or a supercharger. Torque the cylinder head bolts in sequence starting at 25 ft-lbs for the first pass, then another pass to 50 ft-lbs before tightening them to the cylinder head manufacturer’s recommendations. I have used this procedure for many years on supercharged and nitrous-equipped engines without gasket failure. Take the time to go over all the bolts one final time after you have done the final pass, torquing the heads to the manufacturer’s recommendations.

Camshaft Selection and Installation

As I mentioned earlier, using virtual dyno testing with computer software gives you information in addition to that from the manufacturer, but now it is time to make the selection.

In my mind, swapping a camshaft is less work than swapping the cylinder heads. Performing both operations at the same time makes plenty of sense because the labor overlaps and these components are interdependent. Again, cleanliness is the best policy, and torquing the fasteners is important.

This is a typical camshaft swap item. Don’t forget the camshaft assembly lube, which most camshaft suppliers include.

This is a typical camshaft swap item. Don’t forget the camshaft assembly lube, which most camshaft suppliers include.

 

Camshaft Swap

Step 1: Remove Harmonic Balancer

SA247_FULLBOOK_C3Corvette_Page_017_Image_0003Harmonic balancer removal is the first step in camshaft removal and installation. The Shark’s crossmember is in the way, making it difficult to use anything but this long wrench to slowly force the balancer off the crankshaft. To avoid removing the transmission’s torque converter cover to hold the crankshaft during balancer removal, use large channel-lock pliers to hold on to the balancer removal tool.

 

 

 

Step 2: Remove Timing Gear

SA247_FULLBOOK_C3Corvette_Page_017_Image_0004The small- and big-block crankshaft timing gear is pressed on, requiring a puller to remove it. This three-jawed puller does a good job of easing it off. I try to avoid applying heat with the gear in place, as crankshaft main bearing damage can occur. I also use a stop on the end of the crankshaft to avoid damaging the crankshaft balancer’s threaded hole during puller use. It is a good idea to change this gear even if the replacement chain and gear match the one in place: wear occurs and slack timing chains alter timing and performance.

 

 

 

 

Step 3: Remove Valve Lifters

SA247_FULLBOOK_C3Corvette_Page_018_Image_0001Valve lifters can be very tough to remove from high-mileage engines for two reasons: sludge buildup and mushrooming of the lifter where it rides on the camshaft. My first suggestion is to use carburetor or throttle-body cleaner to soften the oil sludge deposits. Spray the cleaner on the sides of the lifter, then work the lifter up and down to knock off the sludge. This cleaning and working the lifter up and down can take awhile. If you feel that you need a hammer to get the lifter out, it is time to rethink the plan. Either the lifter is mushroomed on the bottom, or the sludge is so bad the engine will not live much longer even if you clean it up. Lifter bore damage can occur if a mushroomed lifter is forced out of the engine block. In that case you need more machine work than a typical rebuild. Bite the bullet and go through the engine, or get that crate engine you were considering.

Step 4: Install Camshaft

SA247_FULLBOOK_C3Corvette_Page_018_Image_0002You can use a cam installation tool. Instead, I use this long numbertwo Phillips screwdriver. When guiding the cam into the cam tunnel, keep the camshaft lobes from cutting into cam bearings as you work the camshaft out and it is seated into the correct position. Slowly move the camshaft to keep the lobes of the camshaft away from bearing surfaces. You can rest the cam on the bearing surfaces to regain a good grip if necessary as the camshaft is removed or installed. The lifters interfere with the cam during installation, so leave them out. The fuel pump needs to be removed to allow the fuel pump pushrod to fall away from the camshaft lobe.

Step 5: Install Camshaft Retainer Plate

SA247_FULLBOOK_C3Corvette_Page_018_Image_0003This is a 1987 or later small-block with factory roller lifter camshaft. Position the camshaft retainer plate on the block. Squirt some Loctite on the screws and torque them to 20 ft-lbs. Early engines (non-roller lifter) do not require a camshaft retaining component unless a retrofit camshaft is installed. High-performance engine builders use a roller bearing under the camshaft gear and a roller button that rides on the camshaft timing cover to keep the camshaft from moving around at high RPM. Follow your camshaft manufacturer’s recommendations regarding the use of a retaining component on roller lifter camshaft retrofits.

Step 6: Degree the Camshaft

SA247_FULLBOOK_C3Corvette_Page_018_Image_0004You need to degree the camshaft. Highperformance engine builders pay careful attention to camshaft timing on every build, and so should you. This is an effort to extract every possible bit of power out of an engine. The use of computer testing software may have indicated that retarding the camshaft timing added horsepower at the top end where you really want it; degreeing the camshaft is the only sure way to know where the camshaft is sitting.

Step 7: Install Harmonic Balancer

SA247_FULLBOOK_C3Corvette_Page_018_Image_0005I am a strong believer in this harmonic balancer installation tool as opposed to using a big hammer to pound it in place. Lisle makes an inexpensive version without a bearing under the forcing nut: it works well for someone doing one or two balancer installs per year. Major automotive parts chains also rent them at a reasonable cost, or you can buy one for about $45. Apply a light film of Never-Seez on the balancer’s inner hub to aid installation, and make sure to apply lubricant to the front crankshaft seal to avoid burning up the seal at startup.

Step 8: Adjust Valve Lifter

SA247_FULLBOOK_C3Corvette_Page_019_Image_0001My favorite way to adjust lifters is to do it while the manifold is off. When it’s done this way, it is much easier to feel the load on the pushrods as the rocker nuts are tightened down. With each cylinder at top dead cylinder (TDC) on the compression stroke, this can be determined by placing the balancer on TDC for cylinder number-1 to begin with. As you watch the number-1 cylinder’s valves during crankshaft rotation, look for the number-1 cylinder’s intake valve to open then close. When that intake valve closes, begin watching the balancer. As the TDC mark on the balancer matches the zero on the timing cover tab, you are now at the cylinder number-1 TDC. Both valves can be adjusted on that cylinder. Rotate the balancer 90 degrees and adjust the next cylinder in the firing order, which would be number-8. Repeat the procedure using the firing order until all the valves are adjusted. The rocker arm adjusting nuts are tightened until the pushrod just begins to have drag on it while trying to rotate it. Once you feel the slight drag, turn down the nut is an additional 3/4 of a turn to center the lifter. All too often the rocker nuts are left loose to avoid lifter pump up at high RPM. But you cannot leave them loose because they beat up the valvestems and can cause them to fail at high RPM.

Step 9: Seal Oil Pan

SA247_FULLBOOK_C3Corvette_Page_019_Image_0002I highly recommended one-piece rubber oil pan gaskets to avoid oil leaks. Apply two beads of hot oil-resistant silicone at the front and back of the oil pan to seal up any imperfections at the corners or in the oil pan itself. Once you apply the silicone to the gasket, put the gasket into the proper position as soon as possible. Within 10 to 15 minutes, the silicone provides good bite to the block surface. If the silicone gets too dry, it skins over and does not grip the metal or gasket. Have all the bolts and required tools ready nearby to keep moving once the pan is put into place.

Once you have all the work completed, you need to fill the crankcase with the proper engine oil and set up the engine for tuning. If you choose a flat-tappet hydraulic or solid lifter camshaft, you need to be very careful about what oil you put in the crankcase. Zinc has been phased out of engine oils as of 2007, which requires you to use a zinc additive to prevent cam lobe wear.  

Joe Gibbs Driven Break-In Oil and others on the market have ZDDP. This additive can be found in engine oils designated as off-road or race blends. The story is the Feds want catalytic converters to last 100,000-plus miles, and the zinc was contaminating them. Engine oil manufacturers, such as Brad Penn, have multiple viscosities available with the proper zinc blended into each quart for long camshaft lobe life.

Kirban Motorsports has ZDDP in 4-ounce bottles to add to your favorite motor oil. Synthetic motor oils for latemodel engines do not have zinc and do not protect your camshaft; you must use the zinc supplement. The best policy is to check the contents of the oil before you drop it in the engine; no zinc, no go.

 

Ignition timing should be checked as soon as the engine fi res up. Connect your timing light and set the base timing to 8 to 10 degrees. If possible, use a timing light that allows you to check the ignition timing advance. If the ignition timing is retarded, high exhaust heat occurs. This can damage valves and also blister the ceramic coating off of a nice set of shiny headers. The timing should be checked to make sure it advances as the RPM rises. If so, lock the distributor down and let the engine reach operating temperature.

Ignition timing should be checked as soon as the engine fi res up. Connect your timing light and set the base timing to 8 to 10 degrees. If possible, use a timing light that allows you to check the ignition timing advance. If the ignition timing is retarded, high exhaust heat occurs. This can damage valves and also blister the ceramic coating off of a nice set of shiny headers. The timing should be checked to make sure it advances as the RPM rises. If so, lock the distributor down and let the engine reach operating temperature.

 

Written by Chris Petris and Posted with Permission of CarTechBooks

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[Guide] 1968-1982 C3 Corvette Bolt-On Mods to Make More Power

Table of Contents

The C3 Corvette rolled off of the assembly line and into the hearts of sports car and performance enthusiasts alike, just in time for the 1968 production year. A car that had been in design since the halfway mark of its C2 predecessor’s run, the C3 Corvette endured some of the automotive industries’ most trying times, weathering the storm, and coming out on the far side better for it.

The C3, or Shark as it was affectionately known, was the brainchild of multiple camp’s attempts at visualizing what the future of the Corvette would hold. Teams led by Zora Arkus-Duntov, Bill Mitchell, and Frank Winchell worked feverishly to give the world what would be the third rendition of the Chevrolet Corvette. Initial plans across the board conceptualized the idea of a mid-engine car, though this was not to be.

To say that the C3 came onto the automotive scene in a time of immense growing pains would be woefully inadequate. Oil shortages led to a reluctance toward gas-guzzling performance car purchases, the onset of new emission standards lead to an ever prevalent game of cat and mouse between engineers and industry compliance, and the nation itself was caught up in a state of unrest. But for every challenge thrown its way, the C3 Corvette soldiered on.

The following is a basic guide to bolt-on modifications for your C3 Corvette.

Spreader Bar

The C3 Corvette is well known for having a level of flex within the frame close to the car’s front end suspension components, that border on the line of being excessive at times. This flex has been widely blamed for inducing a “sagging” condition within the front end and all pertaining suspension components. This high propensity for undue frame flex is commonly noted as being the cause for everything from less than overwhelming handling characteristics, to premature frame cracking and misalignment of door gaps.

A spreader bar assists in rectifying this condition by adding an extra level of rigidity to your C3’s frame. A spreader bar does exactly as its name implies. When correctly fitted, the bar spreads and stabilizes the uppermost quadrant of the frame rails, thereby correcting the aforementioned “sagging” condition, and creating uniformity in frame and suspension geometry. This mod especially shines in conjunction with front end suspension upgrades, as it removes any excessive free play from the affected area and allows your suspension to operate to its full potential in an unabated fashion, bringing your Vette’s handling capabilities to life in a big way.

Eckler’s Aluminum Suspension Spreader Bar

Eckler’s Aluminum Suspension Spreader Bar

Do you want to dive into corners with complete confidence that your C3 can handle all that you can throw at it? If so, then you will be hard-pressed to find as beneficial, yet cost-effective of a mod as Eckler’s line of aluminum spreader bars. The Eckler’s Spreader Bar Kit comes with black powder-coated fittings, spherical rod ends, and an all-aluminum bar.

The Eckler’s Aluminum Suspension Spreader Bar includes all required hardware and can be installed with basic hand tools in approximately ten minutes. This kit is completely bolt-on in nature, requiring no welding or permanent modifications that could negatively influence your classic Corvette’s value. At a retail cost of $105.99, you are sure to be free of buyer’s remorse when purchasing this kit by Eckler’s.

Eckler’s Shark Bite Aluminum Suspension Spreader Bar

Eckler’s Shark Bite Suspension Spreader Bar

Do you own a C3 that is suffering from less than desirable front-end frame flex, but you find yourself in search of a spreader bar that features Shark Bite control arm compatibility? If this sounds like you, then Eckler’s has you covered with their Shark Bite Aluminum Suspension Spreader Bar. This kit offers all of the same frame stabilizing characteristics as the standard Eckler’s Spreader Bar, without the fitment issues that are often prominent in other market offerings.

With the weight reductive qualities of an all-aluminum bar and powder coated fittings for a sleek and seamless look, the Eckler’s Shark Bite Spreader Bar offers everything a performance-minded C3 owner could ask for. If that isn’t enough, at a price tag of only $105.99 is sure to still leave you with plenty of elbow room in your modification budget.

C3 Corvette at the National Corvette Museum

Suspension Mods

Although the C3 featured highly improved suspension over that of its first-generation predecessor, there have been a significant number of technological upgrades that have come along in the years since. This is precisely where suspension mods come into play. A substantial number of aftermarket kits exist that enable a technical-minded Corvette owner to bring their car’s handling and ride quality up to speed, without deducting from its nostalgic value.

Although a certain level of investment in time, effort, and finances comes with a modification of this nature, you will soon leave any reservations that you might have had in the past, upon powering out of a curve while riding on your freshly upgraded suspension. If you want a level of steering responsiveness that will have you feeling as if you are riding on rails, your C3 is prime for a suspension makeover.

Van Steel Tubular A-Arm/ Coilover Kit

Van Steel Tubular A-Arm/ Coilover Kit

The Van Steel Tubular A-Arm/ Coilover Kit puts everything you need to fully customize your C3 Corvette’s ride and handling characteristics right at your fingertips. The coilovers and included spanner wrench that come as part of this kit, make on the fly suspension adjustments a breeze. This allows a Vette owner a level of ultimate control in both ride height and cornering capabilities that were previously not possible with the C3’s stock suspension components.

One of the highlights of the Van Steel Kit is that it is a direct fit, bolting on interchangeably in place of the bone stock factory control arms. This is immensely valuable, as it eliminates the need for any value robbing frame modifications. At a retail price of $2,249.99, you will not only be purchasing quality-handling capabilities at a reasonable price but a piece of mind as well. This kit is backed by Van Steel’s unbeatable lifetime warranty, making this purchase a worry-free proposition.

Eckler’s Stage V Premium Street Handling Kit

Eckler’s Stage V Premium Street Handling Kit

Breathe new life into your C3’s aging suspension with Eckler’s Stage V Premium Street Handling Kit. This kit will provide you with everything you need to bring your Corvette’s suspension into the modern era, including beefier sway bars and polyurethane bushings and end links. This restores factory suspension geometry and significantly reduces body roll.

The list of upgrades within this single kit seems to be virtually endless. This kit also includes redesigned front springs to increase spring rate and Bilstein performance shocks to take your ride to the next level. This reduces front-end dive during cornering and significantly improves handling characteristics. Most would assume that a kit of this nature would set you back indefinitely. However, this couldn’t be further from the truth. At a retail cost of only $1,153.99, this is a deal so good that you will feel as if you stole it.

Aftermarket Exhaust Mods

If you want to ramp up your C3’s performance, one of the first items of business to get down to is allowing your Corvette’s power plant to expel exhaust gasses as efficiently as possible. The principle is simple. Restrictive exhaust causes undesirable backpressure. This backpressure limits engine performance by impeding your engine in its bid to rid itself of leftover gases that are yielded as a byproduct of combustion upon each cylinder’s exhaust stroke. As emission standards became progressively stringent, the relevance of this problem only grew.

This exhaust backpressure commonly serves as a limiting factor in performance gains, as an engine can only benefit from subsequent upgrades if it can first expel exhaust gasses with efficiency. Before you can begin forcing more air through an intake for enhanced combustion, the issue of proper exhaust management must be overseen. By significantly reducing exhaust backpressure, you are boosting your Corvette’s performance, and paving the way for additional performance mods to come.

dougs side mount headers

Let your Corvette exhale deeply with Doug’s Side Mount Headers. These custom-fit headers allow you to reap the benefits of reduced exhaust backpressure, and maximize the potential of any future engine modifications that you have in store. These headers are also built to last. With stitch welded ports and heavy-gauge tubing, you will be presented with a set of headers that are in it for the long haul.

Doug’s Side Mount Headers also feature a machined sealing bead to eliminate leaks and CNC mandrel bent tubing that provides the ultimate in fitment. This kit comes complete with all gaskets and hardware to finish the job in a no-nonsense fashion. At a price point of $564.83, these headers are sure to get the proverbial nod of approval from any performance-minded C3 owner.

Hooker Side Mount Chrome Headers

The Hooker Side Mount Chrome Headers are an excellent addition to any C3 owner’s list of prospective mods. These headers are specifically engineered to offer superior exhaust scavenging, velocity, and decreased backpressure, all of which equates to improved C3 performance. These Hooker Headers also utilize a slip fit design, enabling the side tube to be mated with the collector flawlessly, thus making leakage a non-issue.

With their 4-in-one styling and flawless chrome finish, the Hooker Side Mount Chrome Headers don’t just perform with tenacity; they look the part as well. This kit comes with all required gaskets/ hardware and is backed by a 90-day warranty. Retailing at $1,196.99, you will undoubtedly find yourself with a product well worth the asking price.

Electric Cooling Fans

Electric cooling fan mods have found favor with many C3 enthusiasts in recent years. The reason for this is multi-faceted. One reason is that for maximum engine efficiency and protection, your engine must remain cool under several conditions. Modern technology, and the electric cooling fans that it has brought about, accomplishes this quite well. Another case for electric fans is that many believe that such a mod leads to horsepower gains. However, this comes as quite a hotly contested claim, but the thought process behind the theory reasons that a particular amount of horsepower is expended to drive the C3’s stock mechanical fan.

Perhaps the most commonly cited reason for an electric fan conversion is that such a mod frees up an extensive amount of space in the engine bay. This space comes in handy when performing ever-escalating and intrusive mods to your C3 as time moves forward. Whatever your reason for an electric fan conversion might be, you will certainly be happy with the new sleek under hood look that your efforts yield.

Davies Corvette Dual Electric Cooling Assembly

Davies Corvette Dual Electric Cooling Assembly

Do you want to cut your bulky C3 mechanically driven fan completely out of the equation, while also boosting cooling efficiency? If so, then the Davies Corvette Dual Electric Cooling Assembly will get you headed down the desired path. This unit boasts a 10%-15% increase in cooling capacity. This is made possible with its dual 11” fans and lightweight molded shroud.

This kit by Davies Corvette comes complete with custom mounting brackets and all the necessary hardware to make installation a breeze. It also comes complete with a direct fit, relay driven wiring harness, and matched temperature switch. The Davies Corvette Dual Electric Cooling Assembly retails for $459.99 and would make a worthwhile addition to your C3 mods to-do list.

Derale High-Output Dual Fan Assembly

Derale High-Output Dual Fan Assembly

The Derale High-Output Dual Fan Assembly is guaranteed to take your engine cooling efficiency to a level that would be unimaginable for those accustomed to their stock mechanical units. This Derale unit features twin high output 265-watt fan motors that are relentless in their ability to get the job done day in and day out. For an added level of appeal, this fan assembly also utilizes an ultra-quiet patented skewed blade design that brings unit operation volume down to a whisper.

This Derale unit also creates plenty of working space within the engine bay, as it boasts one of the smallest working footprints of all aftermarket electric fans available. Of added appeal is this unit’s non-finished aluminum shroud that allows C3 owners to paint, polish, or adonize it as they see fit for next-level customization. At a market price of $249.99, we will just say, if you do not already own one of these units, you probably should.

HEI Distributor Conversion

Engine in 1968 C3 Corvette

Through the C1, C2, and early C3 days of the Corvette, points and condenser ignition systems were a way of life. These systems undoubtedly functioned with a suitable level of reliability. However, to say that there have been enormous technological upgrades to ignition system design in the last 40 plus years would be a vast understatement. Points and condenser systems that require periodic maintenance to provide reliable operation have gone by the wayside, giving way to the HEI ignition systems of modern-day.

The points and condenser systems of many early era Corvettes required a physical opening and closing of contacts to provide the collapse in the magnetic field that was required for spark discharge. This, in many instances, led to burnt points, as well as misadjusted gap settings stemming from points rubbing block wear. By upgrading your pre-1975 Corvette’s ignition to that of an HEI variety, you will maximize your car’s reliability and minimize downtime for maintenance.

MSD Ignition Pro-Billet Tach Drive Distributor

MSD Ignition Pro-Billet Tach Drive Distributor

Leave points replacement and maintenance in the past with this MSD Pro-Billet Distributor. This unit’s accurate magnetic pickup, oversized shaft, and vacuum advance make it a solid choice for any C3 owner looking to bring their Corvette’s ignition system up to par with today’s industry standards. This MSD distributor’s billet aluminum housing also makes this unit as durable as it is functional.

The mechanical minded third-generation Corvette owner will also be thrilled to know that the MSD Pro-Billet Distributor’s mechanical advance means that you can custom tailor your car’s timing curve for increased engine performance. This unit also clears the firewall and all factory linkages, making installation hassle-free. At a market cost of $420.26, I feel that we are well justified in saying that this will be a purchase free of buyer’s remorse.

Pertronix Ignitor Conversion Kit

Pertronix ignitor

If you are looking to bring your C3’s ignition system up to speed, without going to the trouble of pulling your stock distributor, then Pertronix has just the product for you. The Pertronix Ignitor Conversion Kit eliminates your Corvette’s points and condenser ignition, instead outfitting your distributor with new magnetic pickups that bring your early C3 into the realm of the electronic ignition era.

One particular point that sets this offering apart from other drop-in electronic ignition conversions is that Pertronix is the industry standard for all others in the market. Their products have been a mainstay of consistency and functionality in the automotive industry for years now. At an easily justifiable expenditure of $90.99, there is nothing holding you back from turning your C3 into a champion of reliability.

Sours: https://www.corvsport.com/guide-c3-corvette-bolt-on-mods/
Widebody C3 Corvette Stingray - Vlog

Custom C3 Corvette Is Pretty Wild

Not everyone will like it, but this thing can move!


For some people, the gift of owning a beautiful, factory-condition 1970 Chevrolet Corvette Stingray is like a dream come true. They bask in the glory of the C3 styling and performance all laid out just the way GM designers and engineers planned during the painstaking development process. That’s fine and all, but not everyone is of the mind to keep their car completely stock.

Then there’s this C3 you’re about to watch in action in the video accompanying this article. A soundtrack of Bad to the Bone plays as it hugs turns on a country road, rips some lovely burnouts, and otherwise shows that unlike the Instagram widebody renderings, this modified ‘Vette has been designed to really perform.

This German C3 owner wasn’t content to keep his car stock, not by a long shot. Rather than just buy some Teutonic performance car or get an Italian exotic, the man had a vision involving taking the C3 Corvette to a higher level.

To push things further, the owner focused on the chassis. He outfitted it with an improved suspension package as well as Wilwood brakes. But chassis improvements only do so much. The engine has been pushed to about 600-horsepower. That’s not too shabby, but those chassis enhancements are probably necessary to balance out the additional power.

As the narrator in the video states, in Germany at least back in the day the Corvette didn’t enjoy a stellar reputation, Instead, German enthusiasts saw it as brash but lacking in performance to back up the looks, like its mouth wrote a lot of checks the C3 couldn’t cash. If you hop on ‘Vette forums now they’ll tell you all about the guy who traded his Ferrari in for a C8, so that’s of course not a problem in any way today, no sir.

Sours: https://www.motorious.com/articles/news/custom-c3-corvette/

Corvette modified c3

Wildest Modified C3 Corvettes

What is it about C3s that inspires such strange modifications?


Car collectors seem to have a love/hate relationship with the third generation Corvette. Unless they're a special edition, they tend to avoid and/or devalue them. Personally, I think the body lines on the C3 Corvettes are fantastic - I've always had a thing for curvy cars. However, I understand the complaints about lack of power, a suspension that is less than desirable, and other valid complaints. That aside, they seem to be the favorite of people who like to take appearance modifications to the next level, with some going into ridiculous territories. Check out our picks of the craziest C3 Corvettes from the wild world of the internet.

This C3 Corvette is modified in a very different way.

The longer you look at this Corvette, the harder it becomes to sort out what's going on. At this point, we're starting to wonder if it's actually a C3 or even a Corvette.

PizzaMan Dan's C3 is pretty well-known around the Corvette forums. This pepperoni wrapped 1972 Corvette isn't the worst thing we've ever seen, and it does kind of make us hungry.

Okay, this one is bad. What the builder was trying to achieve here is pretty unclear, but it would be interesting to see this in motion, just to know if it actually can be driven.

It's the hand sticking out of the 'mouth' that does it for us with this C3 dragon. While trying to find the context of this car, we were reminded of the C3 dragon from Death Race!

This wild movie car comes with a rear mounted engine and everything!

This looks like it might be a George Burris build. Love it or hate it, the body lines are exceptionally well done, this is certainly the work of a professional.

There's so much going on with this Corvette, called the "Hawaiian Hillbilly", so here's a video for the full 360-degrees, there's just no other way to present it:

Check out the coolest classic Corvettes on Motorious here.
Sours: https://www.motorious.com/articles/handpicked/wildest-modified-c3-corvettes/
900HP Corvette C3 vs. 1000HP Nissan GTR vs. 600HP Audi TT-RS - Drag Race !

Finally, my pupils got a little used to the light, and I tried to look around. It turned out with great difficulty. I was lying completely naked in the hall on the table, and my legs were tightly tied to his legs, I could not see my arms wrapped back and.

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What are you. Guys. Do not. I'm your friend's wife. Please let me go.



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