Knowing all the technical aspects of the Gen III V-8 engine is interesting, but more than likely, the information you really want to know is how to improve its performance. That’s why this chapter is about aftermarket components that can be bolted on to the stock Gen III LS1 V-8 engine for power increases. In the following pages, you will see the performance gains of some of the most popular components and combinations of components used to increase power on the Gen III V-8. The chapter starts with simple external bolt-ons and progresses to big-hp, highly involved engine combinations. To put some data behind the combinations, most have their power output documented with dynamometer testing.
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Note that all dyno results shown here are standard corrected, not the OEstandard of SAE corrected. Standard correction is to 29.92 inches Hg at 60 degrees F, while SAE correction is 29.23 inches Hg at 77 degrees F. Usually, standard correction data will be about 10 percent higher than SAE corrected, due to the lower temp and higher density of the standard correction. Also, most of the testing was performed without the FEAD, or front engine accessory drive, installed for simplicity. The alternator, A/C compressor, and power steering supposedly consume about 35 hp.
As you will see, the Gen III V-8 responds positively to many different external performance components, like airboxes, exhaust systems, and intake manifolds. There is no one component that unleashes 50+ hp, but the careful selection of a few components combined with some knowledgeable tuning can produce impressive power gains. This chapter starts with some of the more simple modifications, like adding a freer breathing airbox. Then, you’ll see some of the better combinations being tested in the dyno rooms of LS1 developers. Chapter 6 shows you exactly how to upgrade the top end of a Gen III V-8 for a 100+ hp gain, while Chapter 7 shows you all the details needed to build a 500+ hp normally aspirated, stock-block Gen III V-8.
Where Does Bolt-On Power Come From?
If you have ever wondered why GM, or other vehicle manufacturers, “restrict” power output by not using parts like the aftermarket offers, there is one big reason and a lot of smaller ones. First, most of the simple bolt-on performance components that produce power without major changes do so for a simple reason. When GM engineers begin the development of a certain powerplant, they do so with many external components that don’t have the final durability, refinement, packaging, piece cost, and noise, vibration, and harshness (NVH) canceling devices on them. Some of the more common components like this are the air intake and exhaust systems.
In fact, many of these base components and systems are changed over the course of the GM development and durability evaluation process to meet the extensive requirements for creating production-level powertrains. Many of these requirements conspire to “consume” horsepower — or so most hotrodders would believe. Actually, GM would do anything to keep the power output as high as possible, but an even more important issue to them being a successful automobile company is that they not alter the requirements needed to exceed their extremely high quality and durability expectations.
Essentially, if GM were building racecars, then noisy, short-fuse power would be okay. But they’re building highly refined street vehicles that most of the public wants to drive without hearing the engine running for hundreds of thousands of miles. So, the powertrain engineers work backwards to end up with quiet, smooth vehicles.
A good example of this is GM adding sound canceling devices, called Helmholtz resonators, into the intake tubes to minimize the valvetrain and intake air noise that emanates from under the hood. Since the GM engineers started the powertrain development process with intakes that didn’t have the final noise canceling features in them, the base computer calibrations have values in the tables and some simple learn features to run the engine in the “noisy” mode.
This is where the aftermarket comes in. They reverse engineer components, like intake air tubes, that don’t have these noise-canceling and power-consuming features. Also, they don’t have to adhere to the same technical specifications as the production engineers do on cost, packaging, materials, durability, crash testing, and other parameters. This freedom allows the aftermarket manufacturers to increase the airflow into the engine.
With the less restrictive air inlet, the mass airflow (MAF) sensor reads higher airflow into the engine and the powertrain control module (PCM) looks up the required fuel ratio in a different area of the calibration to increase the fuel being injected into the engine. And since the calibration has the values in it or a learn function, the powertrain experiences an increase in power.
The main negative from the installation of many of these performance components is the vehicle will experience an increase in NVH. But since most automotive enthusiasts want to hear the powertrain doing its thing, as they equate this with increased power production, this works out to everyone’s advantage.
Hot Rod Development
There is another subject that should be discussed regarding the aftermarket industry. Unlike the time- and moneyconsuming durability testing and validation GM performs on all of their production components, the aftermarket sees much of their component evaluation done in the field in backyard garages all over the world.
As this book is being written, GM is spending about $400 million a month on warranty claims, so they can’t afford to sell anything they aren’t confident will work impeccably in practically any situation on the road. If your aftermarket component fails, you will sometimes get a new component. But often, the consumer understands they are developing their own powertrain and sometimes they will exceed the capabilities of the part. When this happens, they’ll need to step up to a more durable component or buy a replacement part and do something different so as not to repeat the situation that failed the part.
Neither situation is better than the other by itself. If the factory warranty matters to you, then you need to honor GM’s wishes to maintain it. If you aren’t concerned with voiding the warranty or having a few failures along the way to engineering a “better” powertrain, then making major changes to the powertrain will be very satisfying.
There are many more components on the market than the components shown in this chapter (see the sidebar Gen III Power Parts on page 76) and more on the way. This overview is intended to show some of the potential of the Gen III V-8 with regard to aftermarket components.
Note: If you are comparing dyno charts within this chapter, you’ll notice the power figures don’t correspond for various upgrades. That is because the parts were tested on different engines. You should pay attention to the test-bed engines being used to test the parts, as they will have a strong influence on the outcome of the test. For example, a highflow airbox will probably add more power to a fully built race motor than it will to a bone-stock engine.
Whether you own a Camaro, Firebird, Corvette, or full-size GMC or Chevy truck, all will respond positively to the installation of an aftermarket air intake tube and air filter. This is a good first modification, as any other power increasing additions need more air to make power, which the performance airbox and air filter will provide
Installing an aftermarket air filter and tube usually can provide a lift of anywhere from 7 to 15 horsepower on a Gen III V-8 engine. The systems being sold vary in the horsepower they provide based on their design and the vehicle platform. Most of the Camaro and Firebird aftermarket companies sell just an airbox lid and air filter, while most of the aftermarket Corvette airbox companies sell a complete replacement tube and air filter unit that installs in place of the factory airbox. For the full-size GM trucks and SUVs, most aftermarket companies sell replacement tubes, airboxes, and air filters.
Many of the production GM airbox engineers attribute much of this power increase to the elimination of various noise canceling equipment in the intake tract, being able to spend some more money for a smooth inlet tube, and going to an open-element air filter. To get the full power increase possible, shield the air cleaner from the hotter underhood air so it will breathe cooler ambient air for the maximum power increase.
While open-element air filters work great in performance applications, there are plenty of reasons why GM doesn’t sell their vehicles with these types of air filters. The biggest issue is the noise generated by the intake air rushing into the engine and the valvetrain noise emanating out of the intake tract. While performance enthusiasts find this noise music to their ears, much of the public doesn’t enjoy listening to it.
Other issues to be aware of include what GM calls water ingestion. This refers to the ability of the air filter housing and tube to allow the engine to breathe in air without ingesting water that is either standing on the road or falling from the sky. The automobile manufacturers perform extensive testing to make sure their vehicles can be driven during heavy rains without causing the engine to suck in a deadly amount of water. This is not to say the aftermarket air filter systems won’t pass these tests, just that they haven’t been through this testing.
Usually, performance enthusiasts enjoy a little noise from the engine bay and understand the quirkiness brought on by the use of certain performance components, so these issues are not a problem, but it is important you know they exist.
In general, installing an aftermarket air filter housing and inlet tube on a Gen III V-8-powered vehicle usually requires little more than some wrenches, screwdrivers, a radiator hook tool, and possibly a drill to create a mounting hole. Most aftermarket performance airboxes on the LS1-powered cars are a direct bolt in, requiring no drilling or additional components.
Gen III LW/LR/LQ V-8-powered trucks and SUVs have similar hose clamps and connectors as the cars, but also often have a few fasteners holding the rather large airbox and tubing in place. The aftermarket airboxes usually use a fastener or two to hold them in place, but often not the factory fastener holes — so new holes will sometimes need to be drilled in the radiator core support or fender support to hold the performance airbox in place.
In general, the performance increases these units provide for the amount of work required to install them makes these a popular addition to these vehicles.
Power Production and Dyno Test Details
As a note, these dyno figures, and the other dyno figures shown in this book, are standard corrected, not the SAE corrected figures used by the automobile manufacturers. In general, the standard numbers usually are about 10 percent or so higher than the SAE numbers. Also, many of these tests were performed without the accessories, which means there were no losses from the alternator, A/C compressor, and power steering pump. These accessories can consume 35 horsepower or more.
GM has spent considerable engineering and tooling money to develop a costeffective, free-flowing, lightweight, nylon intake. Since the stock intake has such thin wall thickness, porting the stock intake passages is not an option. The F.A.S.T intake manifold is an ingenious revision to the one-piece, nylon production intake manifold. F.A.S.T has tooled up a three-piece intake that produces a noticeable lift in an LS1’s power output.
The F.A.S.T. intake can be ordered with either the factory opening, or set up for a F.A.S.T./Wilson 90-mm billet throttle body for high-horsepower applications.
The F.A.S.T intake manifold bolts onto any Gen III V-8 just like the production intake, and the throttle body/inlet tube mounts in the stock location too. It is probably a 30-minute job for an experienced hand, and maybe an hour or so for someone who has never pulled an intake manifold. While that hour or so might sound optimistic, remember the Gen III intake doesn’t have a water crossover or distributor. Simply remove 10 bolts, remove some wires and hoses, pry off the stock intake, clean the port gasket face area, install the new intake with new gaskets, tighten down the bolts, and reinstall the wires/hoses. Done.
Performance Camshaft and Valvetrain Components
Changing the camshaft on a Gen III V-8 holds a lot of potential for a variety of reasons. First, the initial Gen III engines had common camshafts for manufacturing simplicity and cost containment. This led to compromises in power production, but that’s good for performance enthusiasts, as there is power available with just a cam swap. Second, the stock LS1 and truck/SUV intake and exhaust systems have the ability for increased flow, especially on the 4.8- and 5.3-liter truck engines, as those systems are built to handle up to the 6.0-liter engine
If you are new to cam swaps, consult many sources before making a change.Valvetrain combinations can be confusing and cause considerable damage if miscalculated, so the more data you can gather from knowledgeable sources, the higher the chances of increased power without any problems.
The worst situation would be the valves hitting the piston tops while the engine is rotating. This is catastrophic to the engine operation. The best way to avoid this is pull the cylinder heads, put a dime-sized dollop of modeling clay on the lowest point of the intake and exhaust valve faces where they might hit the pistons, and reinstall the head. Then, slowly cycle the engine through a full combustion rotation and remove the head to measure the thickness of the clay where the valve contacted it. This thickness should not be less than 0.160 inch.
The Gen III cams are straightforward to remove, just pull the valve covers, relax the rockers, pull the pushrods, rotate the cam 360 degrees to nest the lifters in their retainers, and slide the cam out. Use a long 3/8-inch extension slid up inside the gun-drilled cam for leverage when you’re removing it.
Before installation, lube up the new cam with engine oil on the lobes and bearing surfaces. Also, with any performance Gen III cam substitution, you should install aftermarket pushrods to handle the increased forces from the more aggressive cam lobes.
Power Production and Dyno Details
Camshafts are the brains of the engine, so the cam choice you make will seriously affect the power production. If you go with a mild street cam, the idle quality and powerband will be smooth and predictable. If you go with a more race-oriented cam, the idle will probably need to be higher, and the powerband will be peakier — which means most of the gain in power will be at the upper reaches of the RPM band. Neither is necessarily better than the other, you just need to decide what you are looking for from the vehicle.
The cam used here would probably be classified as a hot street grind. It has a good idle quality, but leaves no doubt that the engine is a performance piece. The driver would feel the power increase from this cam swap. Also, the addition of a set of better-flowing CNC cylinder heads would only make this engine come to life even more, as can be seen in the adjoining dyno numbers.
The baseline dyno engine was an LS6 5.7-liter engine, long-tube headers with 1-3/4-inch primaries, and a Donaldson Blackwing air cleaner. In the chart on page 83 the middle test adds the cam to the engine, and the test on the far right uses the cam and a set of W2W Power Pak CNC-ported cylinder heads.
Here are the specs on the cam:
One of the simplest ways to increase the power to the Gen III V-8 is to install a supercharger. For full-size trucks, the best choice is the Magnuson, and it’s discussed in Chapter 8. Here, we’ll be discussing one of the many centrifugal superchargers available for the car version of the Gen III V-8.
The engine run here could be built with a 5.7-liter LS1 aluminum engine block or a 6.0-liter LQ castiron engine block. The key changes here are this engine has had an aftermarket Lunati crank with a 4.000-inch stroke installed in place of the 3.622-inch stock crank to increase the engine size to 408 cubic inches (or 383 ci if you start with a 5.7-liter block). The iron block was used in this application as it has shown the capability to handle 750+ hp all day long with no problems, while the aluminum blocks require modifications and maintenance to handle these power levels.
The supercharger in this test is a ProCharger D1SC belt-driven centrifugal supercharger. The engine requires only a small handful of performance components to create a true 800+ hp giant. This engine will need to run on 100 octane street gas.
The 4.000-inch stroker crank drops in without any block modifications required (like grinding on block surfaces to clearance the increased stroke crank). This engine has aftermarket rods and pistons, so checks were done to make sure the rods cleared the cam (they should), and that the number-8 piston is machined to clear the crank sensor wheel.
The ProCharger D1SC supercharger kit comes with all the necessary components for installation. If there is any improvement that every supercharger system like this can benefit from, it’s stronger brackets to hold the centrifugal supercharger on the engine. Bracket flex often shortens belt life, increases belt slippage, and accelerates supercharger bearing wear. You’ll never go wrong increasing the stiffness of the supercharger bracketry.
Power Production and Dyno Numbers
The centrifugal supercharger system has the capability of making considerable power when set up properly. They can be sensitive to belt alignment and fueling issues, but with those handled, they usually make good power. Mileage usually suffers with centrifugal supercharger systems.
- Iron block 6.6-liter (408-ci) engine (3.990-inch bore x 4.000-inch stroke)
- ProCharger D1SC centrifugal supercharger, mounting flanges, tubing, etc
- GM LS6-type intake
- CP Forged aluminum, full-dish pistons to achieve 9.0:1 compression
- Oliver billet steel 6-1/8-inch connecting rods
- GM CNC LS6 cylinder heads with 2.02/1.60-inch valves
- Block modified for ARP 1/2-inch head studs
- Aftermarket Comp Cams camshaft (W2W grind)
- Comp Cams valvesprings (PN 266618)
- Lunati 4.000-inch forged crank
- SLP 1-7/8-inch primary headers and full exhaust
- Modified stock controller or, if you’re building a street rod use an aftermarket controller (ACCEL, Big Stuff, Electromotive, F.A.S.T., etc.)
- Stock oil pump with ported outlet and higher-pressure pop-off spring
- BBK 85-mm throttle body
- LS6 85-mm MAF sensor
- 42-lb/hr fuel injectors
- Max supercharger boost of 11.5 psi
While there are many different types of nitrous systems available for the Gen III V-8, the system shown in this chapter is a simple Nitrous Express (NX) 150-hp, wet-flow, single-shot system. While there are port-injected, dry flow systems and injector-ring systems available, the single plate wet-flow system is by far the easiest to install and yet still provides a substantial power increase when the nitrous is flicked on. Usually, wet-flow systems are preferable for up to 150-hp systems. Dry systems that get the additional necessary fuel through larger fuel injectors are usually used for 200+ hp systems.
This NX nitrous system, which was installed on a ’01 Pontiac Firebird, came with all the components to install. The one tricky step is drilling a hole in the intake. This can be done with the intake still on the vehicle by removing the intake tract and placing a vacuum suction tube just below the drilling to catch the chips. Check the pictures for hints on where to mount the solenoids and nozzle.
If you’ve ever driven anything with nitrous, you know what a hoot it is to press the happy button. If you haven’t, you really need to try it. A big power boost is a precarious chemistry experiment, but increases of 150 hp and less are very manageable and very fun. There still is the potential to burn a piston if the fuel solenoid doesn’t open to help out the nitrous, but the chances of this are low with a more conservative setup.
If you don’t know, nitrous is like renting instead of buying because the bottle will need regular refills to keep the engine pumping and bumping. This isn’t the end of the world, just a fact of life with laughing gas horsepower.
Written by Will Handzel and Posted with Permission of CarTechBooks