Easy Ways to Make a Base 1975 Corvette Gain 100hp

Power adders have been used since the earliest days of the automotive industry, and they continue to be a popular method for boosting engine performance cost effectively and reliably. Supercharging (forcing air into the engine) to boost compression was one of the first engine power adders. Turbocharging followed, which used exhaust flow to rotate an air compressor, thereby saving precious horsepower that the supercharger required to add power. Nitrous oxide came later; this uses a compressed gas that could be quickly installed for an instantaneous addition of power.

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All of these power adders were used to increase engine output without major engine modifications. Any of them can be installed on a relatively stock engine to dramatically increase power. For instance, no rolling or rough idle; everyone knows that a radically cammed high-horsepower engine is under the hood. Certainly there are radically built engines designed to optimize the power adders, but the majority of people using them want a stealthy way to be heard. Due to the high cost of supercharging and turbocharging, along with the cumbersome components and plumbing required, some opt for nitrous oxide to get its relatively inexpensive power boost.

Nitrous Oxide

The simplest power adder is nitrous oxide (NOS). It's a cryogenic gas composed of nitrogen and oxygen molecules that have increased oxygen weight, providing a rapidly expanding cool dense air charge into the engine's cylinders. Stuffing more oxygen into the combustion chamber allows you to hang more fuel on those oxygen molecules, and adding more fuel means adding much more power. NOS gives you the best engine performance increase for the cost.

This is your best shot at fitting a supercharger under a Shark factory hood. A low-rise dual-plane intake manifold, such as the Edelbrock 2700 series on a small-block, is the ticket. Each Shark may have different engine-to-hood clearances. Check the fit of the system before buying anything. The Vortec supercharger kit provides 8 to 10 pounds of boost, immediately gaining an impressive 75 to 100 hp.

As the dense nitrous oxide charge rapidly expands, engine compression is enhanced and it can add up to 250 hp without major engine modifications. Doubling your available horsepower, even if it is in short bursts, is something to celebrate. A properly calibrated nitrous system with a full bottle provides an exhilarating acceleration, much like a supercharger boost coming in. Something else to consider: many nitrous kits have discreet components to keep it your little secret that you have an engine enhancer onboard. You can install these systems in a couple of days.

Kit Types

There are two types of nitrous kits: wet and dry systems. The dry system sprays nitrous only, through a single nozzle into the intake system. Dry systems rely on electronic engine fuel controls to compensate for the additional fuel requirements of nitrous. Preferably the nozzle is placed before the mass air flow sensor; keep in mind, the Shark Corvette never used a mass air sensor for electronic fuel control. Although easy to install, fuel enrichment when in nitrous boost is difficult to tune and engine damage can result from a lean fuel condition. Dry nitrous systems capable of boosting up to 50 hp can be safely used with a carburetor. These low-horsepower-boost nitrous systems are used in a stealthy situation for a couple of tenths of a second drop in a quarter-mile blast.

Wet systems work well with carbureted engines that do not have the electronically capable fuel compensation. Additional fuel is sprayed, along with the nitrous, into the intake manifold below the carburetor. The wet fuel aids in fine-tuning the introduction of nitrous. More plumbing and components are required to control the fuel flow while providing much higher horsepower output.

Availability

Before you decide on nitrous as your power adder, check the availability of nitrous in your area. If there are no local speed shops, many drag strips have fill-up stations on-site. You can expect six to eight quarter-mile passes from one bottle; after that, the pressure drops off in a 10-pound bottle with a 150-hp shot kit. Many long-time nitrous users have two or more extra bottles available, especially for a long weekend of racing. There is absolutely no worse feeling when you expect the nitrous to kick in, only to find that you have an empty bottle. As with any addiction, you need to feed it and be aware of your nitrous bottle's fill level.

This wet nitrous kit has a fuel and nitrous spray bar with adjustable orifices for properly mixing the horsepower-enhancing ingredients. All of the pieces are in one box ready to make some serious power gains in one afternoon. You can expect a conservative 75- to 100-hp increase without engine damage if you follow the instructions and carefully install the system. As horsepower levels increase it's not the NOS system that causes problems; it's the engine's rotating components that cannot stand the stress.

Nitrous oxide's reputation is one of those love-it-or-hate-it power adders. Many performance enthusiasts have trepidation concerning the rapidly expanding gas' effect on internal engine parts. Rightly so. You hear about intake manifolds blown off the engine or, worse yet, an engine scattered all over the pavement from the use of nitrous. Intake manifold design is another important factor: single-plane intakes are recommended for proper nitrous and fuel distribution. Dual-plane intake manifolds have upper and lower levels distributing the fuel, air, and nitrous that often cause lean and rich cylinders, with possible engine damage resulting. This holds especially true with 150-hp-and-up NOS kits, which most likely means a raised hood to use a taller single-plane intake manifold on your engine. So much for a stealthy NOS system that you could catch someone off guard with.

Nitrous and Engine Health

Properly working systems with conservative horsepower enhancement do not damage your engine. But the nitrous setup needs to be properly calibrated to each engine so the engine isn't subjected to excessive heat and fails. The addition of any power adder, whether it is supercharging, turbocharging, or nitrous, raises the engine's cooling system requirements due to the compression boost. If your cooling system is in good condition and the engine is running below 200 degrees (unless you are caught in traffic for extended periods of time), 100 hp or less is fine. If the shot of nitrous creates more horsepower, it also creates more heat. Excessive cylinder heat is death to pistons and, in some cases, the engine cylinders themselves when in boost. If the cooling system is marginal, take care of that before adding any additional pressure to it.

You need a baseline to figure what you can expect from your power adder and the engine dynamics. Applying a 200-hp shot of nitrous to a base Shark's L-48 190- hp engine with 100,000 miles is risky and catastrophic engine failure may result. A 200-hp-and-above nitrous kit should have a fresh engine with forged pistons, racequality bearings, and a forged crankshaft for long-term repeated use. However, a 150-hp shot of nitrous is borderline proving to be risky for stock engines with more than 50,000 miles that have had minimal maintenance. Supercharged or turbocharged engines are more susceptible to engine damage at the 150-hp level because the power adder is always on-line.

Typically, Chevy small- and bigblock engines safely handle a 100-hp shot of nitrous for many trips down the drag strip and road miles. This means that the same small- or big-block is perfectly fine with the typical 8 to 10 pounds of boost associated with a turbo or supercharger installation.

This Holley booster fuel pump is being installed on top of the passenger-side frame rail using an aluminum bracket. The supplied rubber-coated clamps and rubber sleeve for the fuel pump keep it quiet to some degree. The bracket is then bolted onto the frame rail; I found it works best to have the mounting bolts on the side for simple pump removal if required. With the body off the Shark, it is obvious that the pump is as close as possible to the bottom of the tank. This prevents loss of fuel suction as the fuel level drops; electric pumps push fuel well, but they do not draw fuel as efficiently. Minimum 12-gauge wire should be used to wire the pump, due to the long run from the front of the Shark to the back end.

Many early Shark distributors can have more than 42 degrees of timing. I have seen some with as much as 58 degrees at WOT or, as I call it, the big bang factor. You should have the distributor tested on a distributor machine; they are dinosaurs and few shops have one but the test is good for your engine's best performance. The ideal is 8 to 10 degrees of base timing. When the engine is idling, I prefer to use a vacuum advance to advance the timing to 20 to 22 degrees. Depending on the engine, most boosted with nitrous are limited to 32 to 34 degrees. Engine compression and boost level determine whether timing should decrease as boost rises. The cost of the test is very reasonable, considering the outcome if the timing is not correct.

The most important part to remember while out cruising with any poweradder system installed is monitoring the engine temperature carefully. Getting stuck in traffic then blasting your way out at full throttle as soon as the road clears can cost you big. Stay calm, let the engine cool down for a mile or so, and once the temperature has leveled off at a safe number (200 degrees or less) you can step into it.

Timing and Fuel Supply

What about the ignition distributor? Is it controlling timing advance properly and does the engine have an adequate fuel supply? Since you are adding cylinder pressure, additional fuel is required to prevent burned pistons from an extremely lean condition. Pay careful attention to the nitrous system manufacturer's recommendations concerning fuel requirements.

To put things in perspective, you could possibly double the horsepower output of your Shark's engine. So a base 210-hp engine could end up with a 200- hp nitrous kit installed that requires almost twice the fuel that the original engine used. Even if the stock fuel system is functioning correctly, it does not mean that the system can handle the additional fuel flow for the nitrous.

The stock fuel pump for a carbureted engine does not provide enough extra fuel flow for a dry nitrous system with more than 125 hp. Booster electric fuel pumps are recommended for all carbureted dry or wet nitrous installations. The carburetor's fuel filter should be changed and fuel lines should be inspected for any cracking or rot that impedes fuel flow (see Chapter 7). The most important thing to do is read the installation instructions for the kit you are installing before taking out the wrenches.

Bottle Placement

You need to figure out where to install the nitrous bottle. The 1968–1977 Shark coupe's rear compartment is one place to keep it out of sight. The 1968–1975 convertibles have limited room for bottle placement when the top is lowered. Of course, you can keep the bottle out of the compartment when the top is down. The 1978–1982 Sharks have plenty of room for the bottle in the rear compartment. The bottle becomes very hot if the vehicle is left out in the sun. A bottle blanket is strongly recommended to keep direct sunlight off the bottle, plus it can conceal your power adder. Summit and Jegs, for example, have many bottle blanket options in a variety of colors and with insulation keep the temperature in check.

Although I have seen bottles installed in the Shark's spare tire compartment with some ingenious planning, I don't recommend this location because you need to drop the spare tire holder every time a fill-up is required. If you go this route, make sure the spare tire holder is secured well; the original single spare tire drop-down bolt could have your stealth system on the pavement for all to see.

There are also 10-ounce bottles for a one-time run or just enough to get you the edge at the top end. These small bottles can be placed just about anywhere. It's best to have multiple bottles, though, to enjoy more play time.

This NOS fuel and nitrous solenoid setup on a highly modifi ed big-block is hidden at the rear of the engine. Where's the ignition distributor? To make sure the supercharged big-block had plenty of spark and was well controlled, a crank trigger ignition was used. Place the solenoids low and out of sight if possible. The Earl's fuel fi lter is mounted on the solenoid plate to keep things tidy and easy to service if required. The aluminum lines are custom bent using tubing benders and careful handling. The aluminum tubing bends and also kinks easily making it delicate to work with. NOS supplies the red-and-blue fi tting nuts; they should be used to distinguish fuel from nitrous. Serious high-performance applications use aluminum tubing. Street-driven vehicles need to use steel or stainless-steel tubing to withstand the rigors of everyday driving. Race-prepped Sharks are checked before each event for wear, cracking, and general health before subjecting the vehicle to race abuse, which makes aluminum lines a favorable choice.

The plumbing for this big-block Vortec supercharged engine had to be carefully planned so the nitrous and fuel lines could be connected to the NOS plate, which was sandwiched between the Holley throttle body and intake manifold. Because the pressurized area lacked visibility, I chose stainless-steel lines for the connection from the solenoids to the plate. The -3 AN tube nut fi ttings were used at each line and then a 37-degree fl are was applied to the lines. A tubing bender was used to confi gure all the fancy radius lines. (I recommend using some inexpensive carbon steel lines to practice with to get the feel for the correct measurements in the radius.) The -3 AN bulkhead fi ttings were used to keep supercharged pressure in and provide a neat line installation. The two aluminum lines connect to the bulkhead fi ttings that supply the fuel and nitrous.

This 1982 Shark has the premium NOS kit installation with Performance On Demand (POD) remote bottle opener, heater, and safety controls. Tank placement is critical to use as much nitrous as possible under acceleration with the bottom of the tank pointing downward and toward the passenger's side of the compartment. This is a safety device that purges the tank if pressures exceed 3,000 psi out of the passenger compartment. The POD controller is placed close to the tank for all the required connections. Once the location is determined, all components must be securely fastened to avoid a projectile in the passenger compartment. You need a helper to install a fender washer, lock washer, and nut from the bottom side. The differential is within a couple of inches of the rear deck so check the bottom side before stabbing a long drill bit through this area. Drilling and cutting holes for the blowoff, supply line to engine, and mounting screws is easily done in the fiberglass deck area.

The Holley throttle body is installed with some additional plumbing required for external vacuum signals. Aluminum tubing was used for the vacuum lines because the tubing would not be under high pressure. The front line goes through a bulkhead fitting to the fuel pressure regulator for the electronic fuel-injection system. The rear line is used for a vacuum or pressure signal to the supercharger system's dump valve to control boost. When the supercharger is spooled up, both of these vacuum lines also have pressure in them and help regulate fuel pressure. All of the throttle body sensors are sealed and use sealed connectors to provide accurate signals to the engine controller. It is also very important that the throttle cable does not hang up on the linkage. If it does the top must come off and that is not quickly done. Be very careful if working in an enclosure such as this. Any leaks can be catastrophic.

Once the bottle location is decided and in place, install the supplied nitrous steel braided covered tubing along the frame rail up to the engine area. Keep the braided hose away from any moving pieces and always remember that the braided hose acts like a saw on just about anything it rides up against and has movement.

Plate System

Installing a plate system is not difficult. In most cases the carburetor is removed. The NOS plate is set in place and the carburetor is installed with fresh gaskets. Solenoids are used to control nitrous and fuel flow. They should be placed as close to the plate as possible. They can be out in the open or hidden at the rear of the intake, depending on how proud you are that nitrous is on your engine. Plumbing the solenoids requires some thought to keep the lines from rubbing or leaking.

Nitrous Flow Control

long engine life. Applying nitrous just above idle can be a major problem as the engine bogs down and fills with excess fuel. Feeding nitrous at threequarter throttle once the engine RPM is above 3,000 is recommended. The engine's momentum makes a smooth transition to nitrous without any hiccups that might cause engine damage.

NOS plate in place with solenoids

Old-school systems used a switch on the shifter and provided the driver with total control. However, if you mistakenly triggered the switch, you could burn down your engine in short order. I recommend using the carburetor throttle activated micro-switch for all installations.

Electronic fuel-injection systems can use the throttle body's throttle position sensor to control the nitrous flow. Use a main electrical cut-off switch to completely shut down the system when not in use. The nitrous and fuel solenoids require adequate wiring to support their high-amperage draw.

Ignition System

The ignition system has highvoltage requirements and is taxed from the added cylinder boost pressure. Sharks from 1968 to 1974 have points and condenser distributors. Certainly they do work and have worked for many years before electronic ignition was introduced as a factory-installed component. Replacing a points-type distributor or converting it to electronic ignition is highly recommended for high-RPM and boosted engines.

Points wear over time, causing late timing and ultimately backfiring, which we dealt with in the early days. Today we no longer need to adjust the points on a regular basis, and ignition performance stays at high-accuracy levels.

Always use an arming switch for your NOS system to prevent unintended operation. The switch can be placed in a readily accessible location for quickly shut down if necessary. This particular switch requires that the upper lever be raised then the toggle switch moved to the on position. If you need to shut down the system quickly the upper lever is pushed downward, immediately closing the toggle switch. The switch is installed inline with the main power supply to shut off all NOS electrical components, so it must be a high-amp switch or a relay for the nitrous and fuel control solenoids.

The tachometer drive is another obstacle and extra cost on the 1968–1974 Sharks, but there are distributors available that drop in, such as the Summit brand HEI or Mallory 75 series HEI distributor. Both units have in excess of 40,000 volts available at high RPM and offer highly accurate ignition timing tuning for your boosted engine.

Crane Cams and Pertronix make electronic ignition conversion kits to save a few bucks and provide more accurate timing for your stock distributor. The kits fit in the stock points location, and you can use your original tachometer drive. Coil replacement is recommended with either of the kits for the best available spark voltage.

You have to be extra careful, though, with the factory distributor's centrifugal advance system: they can be very close to 50 degrees at WOT due to worn components. Do not feed any nitrous to your engine until you have checked the ignition system's total advance. The same goes for a supercharged or turbocharged engine; ease the RPM up and make sure it does not go beyond 36 degrees. The 36-degrees figure is for 100- to 125-hp nitrous and supercharged or turbocharged engines with 6 to 8 pounds of boost.

Distributor Replacement

Replacing the distributor with a high-performance unit is the best move. Often you have just as much invested in converting the ignition control and modifying the timing advance as you do in an all-new distributor. The current distributors can be easily adjusted for proper timing and are far more accurate over the entire RPM band. Keep in mind ignition timing is critical, and even a new distributor may require timing advance correction. Thirty-two degrees of total advance is recommended for the typical small-block: that is, feed nitrous in excess of 150-hp shot, supercharged, or turbocharged with 10 psi or higher.

You have plenty of options for distributor replacement with the 1975–1982 Sharks, although the original HEI design distributor is a very good unit. The Performance Distributors DUI assembly, for example, is based on the original GM HEI distributor. When the ignition system requires high-spark voltage, the DUI unit works very well and the large cap prevents crossfire, which is very important while in boost. This product is for a 100- to 125-hp nitrous system and also works well with a super or turbocharged engine with 6 to 8 pounds of boost.

High-output ignition coils with premium-quality spark plug wires are also recommended. Be extra careful when choosing the ignition-coil-specific OHM resistance. Coils are required for the typical aftermarket ignition conversion. The same goes for the spark plug wires; having the correct resistance is important to match the distributor and coil output requirements. As nitrous, supercharging and turbocharging levels increase, so do the ignition timing control system requirements. Staged timing increments are important when nitrous is at the 150-hp-plus level. Boost controls along with staged ignition timing advance are also highly recommended as turbocharging and supercharging exceed 10 pounds of boost. As nitrous or boost is applied, ignition timing is retarded a few degrees at a time to avoid detonation while still providing enough advance to prevent backfiring from retarded timing. Distributor accuracy is also very important to avoid a hiccup and scattered engine components. Many choices are out there for the boosted engine with performance distributor requirements.

For example, the Pro-Billet line of MSD distributors is a race-bred distributor that requires a separate ignition box to control timing and has a rev limiter, which is always a good idea on a highly boosted engine. Multiple-spark discharge helps performance and it provides higher spark output voltage throughout the RPM band.

Mallory has a number of products from a basic high-output distributor to a high-performance system with a distributor, control box, and coil. On supercharged and turbocharged applications, I prefer to use MSD's latest billet distributor with a 6AL-2 ignition box to plot out the entire ignition timing curve from idle to WOT on my PC. This box works well with nitrous too, using an input from the nitrous-on switch while providing high-output spark voltage all in one unit.

Ignition System

The most important thing to consider is using the manufacturer's complete system and their recommendations, especially relating to the ignition coil and plug wires. Contact your favorite ignition supplier and explain the goals you have in mind. You usually have one chance at getting this right; precise ignition and timing control are very important for long engine life.

Properly gapped new spark plugs should be installed for tuning purposes. Spark plug gaps can be kept at .045 inch as long as the ignition system has a minimum of 40,000 volts available under cylinder pressure.

Once the system has been installed, use the recommended jets for the desired horsepower enhancement. Run the engine for a period and use an entire bottle of nitrous. Pull the spark plugs and examine the insulator and electrode. If any major spark plug electrode or porcelain damage is occurring, stop using the nitrous until you add fuel or modify the ignition timing.

Supercharging and Turbocharging

The use of turbochargers or a supercharger has multiple benefits with noticeable horsepower gains, very drivable from idle to WOT being the most significant. You can easily add 100 hp to a stock engine without fear of engine damage, enjoy a smooth idle, and that set-you-back-in-the-seat feel when boost comes in. You can use these power adders for road racing, autocrossing, drag racing, and spirited driving without worrying about running out of nitrous in the middle of a long run or while out on a hot lap.

The tough part of installing either of these power adders is space limitations and the lack of any specifically engineered kits on the market. It has been many years since Corvette specialty shops have been involved with any supercharging or turbocharging on Shark Corvettes. If you decide to use either one of these power adders, many areas require custom fabrication. From an engineering standpoint the supercharger is going to be easier than the turbocharger to install. Connecting the turbocharger to the exhaust in an already cramped engine compartment is where the difficulty comes in.

Superchargers

Mechanically driven superchargers can produce a verified 80 to 100 hp in street trim. Race trim superchargers can boost horsepower into the high triple digits, depending how much you want to spend. This, of course, depends on the boost pressure and supercharger design. Superchargers also use some additional fuel and rob some of the horsepower due to parasitic drag.

Roots superchargers use rotors to compress the incoming air, then force it into the engine. These superchargers work well at lower engine speeds and produce boost right off idle, plus they look aggressive. As engine speeds increase, airflow and boost efficiency drop off. One major drawback is lack of available clearance under the Shark hood; the Roots supercharger must be mounted directly on top of the engine.

There is only one option to stuff a Roots supercharger under the Corvette hood. Start the project with an LS crate engine, install a Magnuson supercharger that has an integral intake manifold, and use a big-block Corvette hood. The next obstacle is plumbing the air intake system because of the Shark's lack of space around the radiator and core support. Roots-style compressors also require plenty of knowledge in proper fueling and ignition timing to prevent an intake backfire. While not as spectacular as a Top Fueler losing a blower, any Rootsstyle compressor backfire can ruin your day with massive engine or vehicle damage. Roots-type superchargers are typically used on show cars for that visceral look, as they protrude through a cut-out in the hood. Not too practical for any street/strip application; they are destined for the drag strip or show circuit.

Centrifugal superchargers use internal impeller fans to build boost. This requires higher engine RPM to build boost, but once they get going they are quite efficient as engine RPM increases. Their universal design allows more placement options while maintaining a stock hood if that was required. Gear drives are used to speed up the impeller fan to obtain the typical 8 to 12 pounds of boost. Most street-driven vehicles (that are actually driven) often keep the boost level at 12 or below. Early gear drives had very noticeable gear whine; today they are virtually undetectable until engine RPM is increased.

It is possible to stuff a ProCharger or Vortec under the hood of your carbureted Shark and have A/C. Using an aftermarket or big-block hood makes the task a bit easier but it is not absolutely required. The ProCharger supercharger uses an air inlet that attaches to the carburetor where the traditional air cleaner sits, often called a hat style, whereas the Vortec unit supplies the compressed air to a box that the carburetor is mounted in. The box presents a couple of issues. Hood clearance is questionable even with a big-block raised hood. The ProCharger's air inlet allows the use of a stock small-block hood if you desire. In addition, you can adjust the carburetor while the engine is running. The carburetor-in-the-box style requires a lot of lessons to figure out just what to do. Anytime an adjustment is required, the carburetor box cover requires removal. What may sound and feel good with the top off usually is not good once it is all buttoned up and under pressure again.

Chances are the idle air mixture requires tweaking on hot humid or cold dry days; while adjusting you must consider the carburetor has pressure entering instead of normally open to atmosphere air bleeds, skewing the settings. Albeit slight, the pressurized air at idle does require some getting used to during tuning. The carburetor boxes have adjustment plugs to access the idle fuel mixture adjusting screws; if you are lucky that may be all that is required for tweaking the tune. Once you get the hang of how the pressurized air changes the carburetor settings it gets easier. Another thought is, no matter what centrifugal unit you prefer, you can substitute the carb-in-a-box air inlet for a hat style to make tuning easier.

Vortech has a full line of centrifugal superchargers in various trim levels for street, serious street, and race applications. Some are for sustained use on road courses while others have helical cut gears that operate quietly for stealthy Saturday night cruising. They also have a self-contained unit that does not require an oil feed or drain-back lines, which eases installation. Once you feel that you have an idea of your needs, call Vortech to discuss the plan. They make a difficult job easier by helping you choose the correct unit for your application from the multitude of combinations available; they've tackled just about every supercharger installation you can imagine.

To make the tuning task easier and prevent engine damage, a purpose-built carburetor is suggested. Modifying your existing carburetor is possible, but it requires a lot of homework to make it all come together.

This Weiand 142 series Pro-Street supercharger is a low-profile assembly that allows the use of an original Rochester Q-jet carburetor. Of course the carburetor requires modifications and tuning (see Chapter 4). This Pro-Street supercharger can boost performance 25 to 40 percent depending on the application. It has CARB exemption so it is 50-state emissions legal. The supplied pulleys and original equipment carburetor must be used to keep it legal in all 50 states. The visceral look is there, especially with an open hood, which is about the only option for a Shark application even though this supercharger is considered low profile. Weiand has 10 small- and big-block kits including the time tested 6-71 that produces 11 to 12 psi of boost.

Holley has new out-of-the-box carburetors built specifically for supercharged or turbocharged engines. A larger needle and seats with specific floats to prevent collapsing and provide adequate fuel under boost are part of the design. Screw-in air bleeds are utilized for tweaking the idle under pressure, along with manifold pressure referenced power valves for accurate fuel flow under boost. Four corner idle mixture screws are installed to balance the cylinders more efficiently at idle and when the throttle is cracked open. They also come in 600- to 950-cfm air flow for a wide range of supercharged applications. These are perfect for the first-time supercharger endeavor with all the inherent concerns addressed for pressurized installations.

Suppliers such as AED Performance specialize in one-off blow-through carburetors for those who have high-horsepower applications requiring custom tuning. When you get into the 175-plus horsepower enhancement range with your pressurized application, a custom carburetor is required. As you approach the 200-hp range, fuel pressure must rise to ensure adequate fueling at high RPM. Approximately 1 pound of pressure per pound of boost after 10 psi is necessary.

This is when the game gets serious, and the books should come out for a thorough understanding of all the fuel requirements.

Both Vortec and ProCharger make brackets to bolt the supercharger in place on the big- or small-block Chevy engine. The tough part is finding or designing and fabricating the accessory drive brackets if you want A/C and power steering. Of course you need to have the alternator and water pump installation worked out at the very least. You also have to figure out the pulleys that work with the modified accessories. Depending on your situation, you may be able to find GM accessory brackets and components that work; it comes down to spending the time to research the possibilities. You do not have to use Corvette accessory brackets as long as they align the belts and the hood closes.

Plumbing the air intake and compressed air out to the carburetor is all on you, requiring fabrication and a great imagination. Long sweeping bends are required to obtain the most out of the system. Ultimately, once the air intake is close to the front of the Shark the real engineering feat comes in. There is very limited room for any air inlet to pass through the radiator core support to draw cool air from the front of the Shark. The installation of an intercooler is a huge help in making serious power, while preventing engine damage.

Placing an intercooler in front of the radiator as well as routing the plumbing is a difficult task. Depending on the supercharger's manufacturer, it may require an oil feed and drain-back line to the oil pan. While installing a centrifugal supercharger is a difficult project, my recommendation is to consider these aspects and examine the customer gallery photos of 1968–1980 Camaro installations, because the C3 and the Camaro have similar engine compartment restraints.

Turbochargers

Early on, turbochargers were known for a substantial lag time at low RPM. Today's high-tech turbochargers have minimal lag as they spool up and provide boost.

The turbocharger is two systems in one, and requires more plumbing and fabrication than a supercharger installation. An exhaust inlet comes from the exhaust manifold/s along with an outlet that connects to the exhaust system; this spins the turbo fan. On the forced induction side, an air inlet must be used, which then requires a pressurized connection to the intake system.

Twin turbochargers are desired but not mandatory; they balance the exhaust flow without restricting it, whereas a crossover pipe is used on single turbocharger installations to connect the manifolds, creating some restriction. The twin turbo installation requires more complex plumbing, connecting the exhaust system and plumbing the two air outlets. Finding a place for two air filters that draw cool air with the myriad of turbocharger support pieces also requires careful planning. I feel that the turbocharger is the best choice, considering the power enhancement capabilities. Unfortunately, it takes a lot of hands-on fabrication and dollars to be successful.

Designing and fabricating a one-off turbocharger system is not for everyone, unless you understand plumbing as well as engine intake and exhaust systems.

Greenwood Turbochargers

John Greenwood built four turbocharged Sharks: three were considered production models and one was the mule for testing. The Greenwood turbocharged Sharks used a custom exhaust manifold cast by Air Research for the turbo connection to the exhaust along with a waste gate. To utilize maximum exhaust pressure, a crossover exhaust pipe was routed to the manifold that the turbo sat on. Airconditioning was out of the question, with very limited space on the passenger's side of the engine where the turbo resided. Like the supercharged installation, an air inlet was mounted in place of the air filter on a blow-through carburetor. Since then TracoEngineering is the only other turbocharged Shark on the roadways. They have a similar setup with a custom exhaust manifold and blow-through carburetor.

You have to be really lucky to find one of the original exhaust manifolds cast by Air Research, and chances are more than four were cast for the production Sharks. Trouble is, where and how do you go about this monumental endeavor? Casting your own manifold is possible but expensive for a one-off copy; the other option is a custom-built header system, which is certainly more doable. The problem with that is the heat generated by the engine going through the pipes is detrimental to the underhood components. Exhaust temperatures tend to be higher under heavy loads when boost pressure is up and can approach 600 to 800 degrees. Coating, wrapping, and shielding the pipes can help control some of the heat if you really want to be a pioneer in the Shark turbocharging arena.

Callaway Turbochargers

In 1987, Callaway Cars turbocharged new Corvettes for General Motors, making them a true pioneer in turbocharger retrofitting. These turbocharged Corvettes (RPO code B2K) were covered under GM warranty-passed emissions testing and were available in all states except California. Their approach to turbocharging was well-thought-out and very reliable. They place a small turbocharger on each exhaust manifold beside the engine. Intercoolers were placed above the valve covers, then an air inlet connected the two turbo outlets to the tuned port intake. They used a custom-built exhaust manifold composed of stainless-steel tubing for the installation.

Now for the reality of it all: the option that added 105 hp was $20,000 for a base vehicle that cost approximately $30,000. This was thanks to the extensive engineering required to make the turbocharged Corvette a true street-driven powerhouse. Certainly it can be done for less money, but not for any driver who gets behind the wheel, which is a must when a manufacturer is building cars. If you put together something at home and end up on the side of the road, sure you'll complain, but it's easier to shrug it off than if you put out big money for it. The bottom line is, it takes time to think out and engineer each portion of the install, including numerous necessary heat shields. You must be concerned with any component within 2 to 3 inches of any exhaust component, including the turbocharger.

Turbocharger Installation

Once the turbocharger is mounted to the exhaust manifold(s) the plumbing begins, preferably to an intercooler then to the carburetor or throttle body. Summit Racing, Jegs, and Superchargersonline.com have many tubes and couplers available for the plumbing. Unfortunately, you have to use the trial-and-error method to find the plumbing pieces that fit your application.

A mandrel pipe bender for 3-inchor-bigger pipe can help. One of my tricks is to use thin-wall PVC pipe (typically 3-inch) to fabricate the required tubing. Once I'm happy with the routing and fit, I have it as a sample for an aluminum fabrication shop's working drawing.

Another trick is to use poster board to make an air inlet, for example, and then cover it with fiberglass. When the fiberglass dries, the paper can be removed. The rough inlet is final-shaped and another two layers of fiberglass are added.

You need flexible coupling to connect the long runs of tubing to the air box or carburetor hat. No matter what tubing you are using, it is always a good idea to have a flex joint to allow some movement and isolate the heat if possible. At least on the turbocharger's outlet to the carburetor, you are working with somewhat simple-to-modify components. When it comes to connecting the exhaust out of the turbocharger, it takes some thought and a mandrel tube bender for the best performance.

Like a supercharger, a turbocharger requires an oil feed and drain-back line to lubricate the blower wheel bearings. Turbochargers can spin up to 20,000 rpm and must have clean oil at all times or major damage can result. The damage to the bearings is minimal if the rotor hits the housing and either component requires replacement.

Clean oil is mandatory and should be changed at a minimum 3,000 miles or pay the consequences. It is also very smart to let a turbocharged engine idle for 5 to 10 minutes after a long hard run to slow the turbo down and stabilize the engine temperatures. The hot oil cooks in the drain-back line and eventually clogs the line, limiting oil flow, and the result is major turbocharger damage. Timer systems are available to shut down the engine after a cool-down period. The ignition is shut off and the timer takes over monitoring the engine temperature and timing the event. When the required amount of time has passed, the engine is shut down automatically.

Intercoolers

Supercharged and turbocharged engines build heat from the air being pushed through the intake system, adding to the already hot intake air. Roots superchargers build as much heat as turbochargers. Centrifugal superchargers are the coolest-running but they too benefit from cooler air. To combat the inherent heat buildup and gain more horsepower, intercooling was devised, routing the pressurized air through a radiator device at the front of the vehicle to cool the air before it enters the engine. The benefits are twofold: better engine performance and less chance of pre-detonation that takes out pistons.

The problem is, where do you place this additional radiator? It did not have to be as big as the radiator in the Shark; it could be two units if twin turbocharging was used. One way of solving this problem was to lay the existing radiator down at a greater angle. The lower radiator accomplishes two things. It provides an area for the intercooler and a place to route the air inlet and outlet tubing.

This sounds easy on paper, but it means a custom-built radiator core support and most likely bumper support modifications. Intercoolers have been laid flat so that the hood can be sealed to them and an opening cut out for cool air to flow through them. Of course, once the intercooler is placed it must be plumbed, and that can be as difficult as the installation.

There are other ways to combat the heated air entering the engine with stand-alone injection systems. Some of the early designs used water and alcohol injection to cool the intake charge; others used windshield washer fluid. Adding the water and alcohol decreases cylinder temperatures and decreases the chance of pre-detonation.

Today's sophisticated systems use electronic controllers to handle water, alcohol, and methanol injection for precise injection flow at the requirements for the boost level. AEM, for example, has complete systems that are much easier to plumb into your boosted engine than it would be to design an intercooler.

The systems work, although they require a reservoir and filling on a regular basis. I have also found that the systems are fine if used regularly; if not, the injector nozzle can clog and limit or prohibit the much-needed flow of cylinder cooling fluid. Well-thought-out systems have warnings when the fluid is low or no flow has occurred. So there is an alternative to the ultimate intercooler setup for a pressurized Shark.

While it may sound cool to have a pressurized system on your Shark, it comes down to dollars and cents. Over the long run, this is a costly upgrade for the power gain.

Written by Chris Petris and Posted with Permission of CarTechBooks

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Source: https://www.chevydiy.com/c3-corvette-how-to-add-power/

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