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Performance Parts and Modifications Explained

 

Don't let aftermarket parts scare you!  Many of them are extremely high quality pieces, equal or better in quality to their factory GM counterparts.  Not only do these parts improve performance, but they often increase gas mileage as well by improving the efficiency of the car's engine.  Make sure you do your research before buying and installing aftermarket parts, as many of them differ in quality, particularly on earlier cars.  Also, know how your performance parts can affect your factory warranty, if your Corvette is still covered by one.

Interested in having performance parts installed on your Corvette? 

See our Add-On Performance Parts page or contact our Service Department at (678)395-3957 for a quote today!

 
Aftermarket Camshafts

Aftermarket Camshafts 

One of the more exotic and skilled upgrades, camshafts can take quite a bit of time to install, but yield one of the best bang-for-the-buck values for the do-it-yourselfer.  The camshaft is located inside the engine block, and rotates with the crankshaft, as the two are tied together via the timing chain.  The camshaft's job is to open and close the valves in the cylinder heads, allowing air to come in, and exhaust gases to be expelled.  Camshafts are available in a great variety of shapes and sizes, allowing the owner to choose how much power they desire at certain RPMs, generally at a cost of drivability in terms of gas mileage and smoothness of idle.  Some camshaft manufacturers can build a "custom grind" camshaft, built to your exact specifications with your car's other modifications and your driving habits in mind.  Compared to nearly all foreign cars and even V8 Mustangs, camshaft upgrades on Corvettes are very inexpensive in terms of parts, as GM's engines use a pushrod design with a single camshaft instead of costly multiple camshaft setups.  Some camshafts may require new valve springs to be installed as well, particularly when going with larger cams.  Tuning of some sort is almost always required when installing a camshaft for a smooth idle, maximum power, and drivability.  Available for nearly all cars.

Cost: $150-400 (expect more for cams requiring new valve springs)

Install Difficulty Level: Expert

Requires Specialized Tools: Yes

Typical Gains: 5-50hp

 
Aftermarket Carburetors/Throttle Bodies

Aftermarket Carburetors/Throttle Bodies 

Aftermarket Carburetors/Throttle Bodies

Once the heart of an engine's fuel delivery system, carburetors became obsolete with the advent of computer-controlled fuel injection systems in the early 1980s.  Although small in their footprint, carburetors combined the throttle body, fuel jets, and all fuel and air metering tasks.  Thus, aftermarket carburetors make more power by increasing the amount of air and fuel going to the engine, as well as using the entering air and fuel more efficiently.  The 1981 Corvette is unique, as it is the only year that came equipped with a computer-controlled carburetor, allowing for slightly more accurate fuel metering from the factory.  Consequently, it is very difficult to properly install an aftermarket carburetor on a 1981 model without seriously modifying the car's computer and emissions equipment.  The 1982 and 1984 Corvettes were equipped with Crossfire Injection, which was an exotic dual throttle body injection system, appearing similar to two small carburetors.  Crossfire Injection is best explained as a hybrid of a carburetor and a true fuel injection setup.  Although plagued by word-of-mouth from amateurs frustrated with its intricacies and special parts, Crossfire Injection cars run just as well as carbureted or fuel-injected cars when tuned properly. Although used for a very short period in Corvette history, GM found Throttle Body Injection (TBI) setups like the 1982 and 1984 Corvettes to be very efficient on other vehicles, and still uses a form of TBI in the base engine of their current model year full-size truck.  Like the 1981 computer-controlled carburetor model, 1982 and 1984 Corvettes with Crossfire Injection are very limited in terms of upgrades, other than switching over to a complete fuel injection or carburetor setup.  Additionally, most aftermarket carburetors require some tuning out of the box, and it is becoming increasingly difficult to find shops that have competent carburetor technicians other than carburetor specialty shops.  Nearly all aftermarket carburetors will require an intake manifold adapter plate and several other inexpensive modifications to fit and function on an otherwise stock engine.  Additionally, carburetors come from the manufacturer with variety of options and air flow (CFM or Cubic Feet per Minute) ratings.  Be sure and get the carburetor that is right for your car, based on your engine's size, power, computer requirements, and whether or not you have a need for an electric choke and vacuum secondaries. 

The equivalent of the carburetor in 1985-up cars is the throttle body.  Unlike carburetors, the throttle body's only job is to open to let air into the intake manifold when the accelerator is pressed.   Aftermarket throttle bodies have larger openings than their factory counterparts, allowing for more air to enter the engine, creating more horsepower.  Throttle bodies do not do any air metering, as all air metering is handled by the Mass Air Flow sensor (MAF), or speed density system on earlier cars, before it enters the throttle body.  The task of getting the fuel to the engine on these cars is handled by a significantly higher pressure, in-tank fuel pump and fuel rails containing the actual 8 fuel injectors.  All throttle bodies have crucial electronic sensors attached to them, which generally are removed and then re-installed on aftermarket throttle bodies before installation.  Aftermarket throttle bodies generally do not require any tuning to work properly.  Relatively inexpensive and very easy for the novice to install, aftermarket throttle bodies are great for anyone looking to free up a couple horsepower with a minimal investment of time and money.

Cost: $200-500

Install Difficulty Level: Advanced

Requires Specialized Tools: No

Typical Gains:  3-15hp

 
Aftermarket Cylinder Heads

Aftermarket Cylinder Heads

Aftermarket Cylinder Heads

Generally referred to as just "heads", a car's cylinder heads contain all of the valves and associated components necessary to feed air to the engine and then remove the resulting exhaust gases.  Heads are a relatively expensive upgrade, and are generally only installed on cars whose owners are looking for maximum power.  On older engines, most factory cylinder heads are made of iron, which is strong but very heavy.  Aluminum heads were available from the factory on certain engines on earlier models, but did not become standard until the later part of the 1986 production year.  Aftermarket aluminum heads are not only lighter than their iron counterparts, but also feature much larger as and smoother intake and exhaust ports, resulting in phenomenal power increases.  In fact, many modifiers choose to simply polish and bore-out or port the factory cylinder heads, which still yields very good power increases for minimal parts cost, while sacrificing some strength and reliability.  Heads are generally sold one of two ways: bare, with just the heads and no other parts, or ready-to-install with all valves and related components.  Like camshaft upgrades, heads usually require tuning for maximum power and drivability.  Cylinder head upgrades are particularly effective on 1971-81 cars, as federal emissions requirements for those years mandated that the factory heads use smaller ports in hopes of achieving better gas mileage.  Unfortunately, these "choked" head designs did little for gas mileage, but greatly decreased the power that these cars made.  Available for nearly all cars.

Cost: $800-4,000

Install Difficulty Level: Expert

Requires Specialized Tools: Yes

Typical Gains: 5-50hp, also up to 50 lbs in weight savings on cars originally equipped with iron heads

 
Aftermarket Distributors/Caps/Rotors/Ignition Coils/Spark Plug Wires

Aftermarket Distributors/Caps/Rotors/Ignition Coils/Spark Plug Wires

As factory ignition systems are fairly efficient when working properly, aftermarket ignition parts should be considered only for those with engines that already have all other possible upgrades, or those looking simply to dress-up their engine bay.  Although aftermarket ignition parts are proven to show power increases, they rarely show a great increase over the same factory parts in cars with mostly stock engines.  Available for nearly all cars.

Cost: $30-400 (per part)

Install Difficulty Level: Moderate to Advanced

Requires Specialized Tools: No

Typical Gains: 1-20hp

 
Aftermarket Intake Manifolds

Aftermarket Intake Manifolds 

Aftermarket Intake Manifolds

Not to be confused with the cold air intake, intake manifolds are bolted directly to the top of the engine,  and are the final stage in feeding air to the engine.  In non-fuel injection cars, factory intake manifolds are usually made of iron.  In this case, aftermarket replacement intakes are made of aluminum, and save weight as well as make more power.  Aftermarket intakes for carbureted cars are generally much less expensive than their fuel-injected counterparts, and can usually be optioned with a variety of provisions for cars with emissions equipment.  However, some additional modifications may be necessary to accept an aftermarket intake on later model carbureted cars.  TPI cars (1985-91) have complex aluminum upper and lower intake manifolds, making them much more costly to upgrade.  Nonetheless, great power increases can be had with aftermarket TPI intake setups as the factory intake is fairly restrictive on these cars, particularly in the upper RPM ranges.  LT1 and LT4 cars (1992-96) have a single aluminum intake, and all LSX cars (1997-current) have a similar setup, constructed not from aluminum, but from composite materials.  Note: carbureted cars, particularly earlier ones, have little clearance between the air cleaner and hood from the factory.  Aftermarket intakes make power by allowing more air to flow through them, and usually accomplish this by being much larger than the factory unit.  Consequently, this can cause a clearance issue with the hood.  Therefore, make sure the intake you are looking at will clear your hood.  Available for nearly all cars.

Cost: $150-2,800

Install Difficulty Level: Advanced

Requires Specialized Tools: Only on models with Fuel Injection

Typical Gains: 5-30hp, plus weight savings on cars originally equipped with cast iron intake manifolds

 
Aftermarket Shifters

Aftermarket Shifters

These units replace the factory shifter in manual transmission cars.  The main advantages to an aftermarket shifter are shorter throw distances between gears, and stronger stop points for each gear.  Factory shifters often feel rubbery, particularly in 1984-up cars.  An aftermarket shifter not only makes it easier to find gears, but also gives the driver a greater feel for the car and which gear it is in.  Not all aftermarket shifters are equal; some manufacturers use considerably shorter sticks, which can limit leverage and make it difficult to shift gears.  Like catback exhausts, it is better to try out a shifter yourself before deciding if it is right for you.  Available for nearly all cars.

Cost: $150-350

Install Difficulty Level: Advanced to Expert, depending on generation

Requires Specialized Tools: On some models

Typical Gains: None, although quicker shifts from an aftermarket shifter can equal faster lap and trap times for those competing in roadracing and NHRA events

 
Catback Exhaust

Catback Exhaust 

These kits replace all factory mufflers and pipes located downstream from the catalytic converter (hence the name catback exhaust).  One of the most popular modifications, these systems range in quality, construction, sound, and prices.  Catback exhaust systems make power by reducing the amount of backpressure in an exhaust system, allowing for more exhaust gases to be expelled more quickly, thus allowing more air and fuel to enter the engine's combustion chambers.  Be leery of anything not made of stainless steel -- these systems WILL rust, even in Southern climates.  Most kits do not require welding, although it is still recommended for factory-quality fit.  A catback exhaust system has a greater influence on the sound a car makes than any other modification -- therefore, make sure that you choose the system that is right for you.  Many systems produce an aggressive sound, however some louder systems can produce a "drone" that can make driving unpleasant.  It is highly recommended that a customer listens to or drives a car with the catback system they are considering before making a purchase as there is such a high variation in sounds.  Available on nearly all cars.

Cost: $300-1,700

Install Difficulty Level: Advanced

Requires Specialized Tools: No

Typical Gains: 5-15hp

 
Headers

HeadersHeaders

Headers

Headers attach directly to the engine block and replace the factory exhaust manifolds.  Like catback exhausts, headers come in a variety of price ranges and quality.  Headers come in three lengths: shorties, midlengths, and longtubes; however, not all lengths are available for all Corvette generations.  Headers make power by providing a much larger area for exhaust gases to travel than factory exhaust manifolds, once again allowing more air and fuel to enter the engine.  Generally speaking, the longer the headers, the greater the performance increase.  However, longer headers can cause clearance and scraping issues, particularly on newer cars that have been lowered.  Additionally, some header kits do not include catalytic converters or provisions for rear oxygen sensors, which can be a problem for later model cars registered in counties with emissions testing.  Even with catalytic converters and rear oxygen sensors installed, some header systems can still cause a check engine light to come on, generally related to oxygen sensor readings.  This can be overcome with tuning, although this can be costly.  Headers are generally available in three different finishes: black painted, ceramic coated, and stainless steel.  Although inexpensive, black painted headers usually rust quickly and can be a real eyesore in an otherwise clean engine bay.  Ceramic coated headers are usually a glossy silver finish, which looks great for years if not scraped by speed bumps.  Some manufacturers of ceramic coated headers offer a lifetime finish warranty, which is helpful down the road as extreme exhaust temperatures and scrapes from improperly-maneuvered speed bumps can wear away the coating.  Stainless steel headers are generally the most expensive, and are usually a dull steel color.  As one might suspect, stainless steel headers do not rust and never have to be recoated.  Available for nearly all cars. 

Cost: $200-1,500

Install Difficulty Level: Advanced

Requires Specialized Tools: No

Typical Gains: 5-25hp

 
K&N FIPK/Cold Air Induction Kits

K&N FIPK/Cold Air Induction Kits

K&N FIPK/Cold Air Induction Kits

Although these kits make use of reusable air filters, the main advantage over just a reusable air filter by itself is the replacement of the factory air box and its location.  Cold air kits generally have much larger filter elements than stock units, and are usually mounted in a location where there is more outside or colder air available.  Thus, these units make their power by delivering cooler air in greater densities than their factory counterparts.  The equivalent for carbureted cars, aftermarket air cleaner assemblies are available for non-fuel-injected models, but serve little purpose other than engine dress-up as the factory units are relatively efficient.  K&N FIPK and Cold Air Induction Kits are available only for modern fuel- injected cars (1985-up).

Cost: $200-400

Install Difficulty Level: Beginner to Advanced

Requires Specialized Tools: No

Typical Gains: 5-15hp

 
K&N/Reusable Air Filter
K&N/Reusable Air Filter

Commonly misconceived as an inexpensive way to make great power, the main advantage of the K&N type air filter is its reusability.  Although a small gain in power is possible, the gain is usually negligible and cannot be felt simply by driving the car.  Nonetheless, this is an excellent and inexpensive mod for anyone who is going to keep their car for at least a couple of years, at which time the filter pays for itself as replacements are not necessary.  Available for nearly all cars.

Cost: $40-80

Install Difficulty Level: Beginner

Requires Specialized Tools: No

Typical Gains: 1-3hp

 
Underdrive Pulleys/Aftermarket Harmonic Balancers and Dampers

Underdrive Pulleys/Aftermarket Harmonic Balancers and Dampers

Underdrive pulleys create horsepower by reducing the amount of rotating force given to an engine's accessories (alternator, a/c compressor, water pump, power steering pump), thus making more power available to the drive wheels.  Aftermarket harmonic balancers and dampers work in a similar fashion, but limit the amount of power given to all of the engine's accessories at the source, since the harmonic balancer/damper bolts directly to the crankshaft, and is responsible for turning all accessories on the front of the engine with the help of the serpentine belt.  In some cases, an overdrive pulley is required for the alternator when an aftermarket harmonic balancer/damper is used, as some alternators have to be spun at rates closer to the factory specifications in order to provide adequate power for the rest of the car.  Available for most cars.

Cost: $170-300

Install Difficulty Level: Advanced

Requires Specialized Tools: Yes

Typical Gains: 5-20hp

 

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