There are many fans of the iron-block 4.8-, 5.3-, and 6.0-liter Gen III V-8s that power many of the ’99 and later full-size Chevy and GMC trucks. That fan base is drawn to the Gen III V-8 because of its thick powerband, impressive peak power numbers, and good fuel economy. Simply, the Gen III V-8 pushes these 5,000+ pound trucks pretty well in factory form, and with a few performance tweaks, can really make them move out. This chapter gives a few examples of performance modifications that can be made to the Gen III V-8s to create a scootin’ truck or SUV. The installation of superchargers, factory performance cylinder heads, and turbocharger kits shown here will work on any of these three engine configurations, but as usual, you should know the bigger the displacement of the engine, the more power it should make overall.
This Tech Tip is From the Full Book, HOW TO BUILD HIGH-PERFORMANCE CHEVY LS1/LS6 V-8S. For a comprehensive guide on this entire subject you can visit this link:
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For comments and dyno charts on bolt-on component modifications external to the engine, like air cleaner systems, cat-back exhausts, and similar changes, see Chapter 5.
Simple Supercharger Install
The first performance upgrade shown here, the MagnaCharger supercharger kit, is by far the simplest considering its ability to make power. MagnaCharger has created a low-profile intake manifold that allows them to place the Eaton supercharger on top of the engine and still fit under the hood. Installation requires just a little more than removing the plastic intake and replacing it with the MagnaCharger system.
The MagnaCharger kit is surprisingly complete and the instructions are shown in step-by-step, photography-supported detail. There are a few things not shown, like how to remove fuel injector clips and other details, but lucky for you, those steps are detailed here and in Chapter 4 in the full-size truck section. A dyno test was performed to quantify the power increase and the results are shown.
The main reason that a supercharger is such a great way to increase power in the truck Gen III V-8 is the fuel these engines were built to run. Since most consumers for these trucks are concerned with fuel costs, GM designed the Gen III V-8 truck engines to operate on regular 87-octane fuel by optimizing combustion chamber pressure, fuel stratification, and detonation/knock detection. This means there is considerable room for more performance by tweaking the compression ratio, cam specs, and knock controls, if you accept running higher-octane fuel. To put it simply, boosting the inlet charge on the Gen IIIs with a crank-driven blower creates a thick powerband that is truly addictive — so you’ll probably be accepting of the added cost of premium fuel.
The top choice by most enthusiasts for full-size trucks is the MagnaCharger. The common reasons for this are its ease of installation, durability, impressive power production, and limited impact on the mileage. As a general rule, most superchargers offer simple installation, impressive power production, and reasonable cost for the power you get in return. But one advantage the MagnaCharger has over other blowers is a bypass feature at low RPM so the engine can run essentially unboosted, freewheeling the blower. This helps to improve the mileage and is transparent to the driver of the vehicle.
The Magnuson supercharger system shown here is being installed on a Hummer H2 LQ4 6.0-liter V-8. The LQ4 is ideal for supercharging because of its 9.41:1 compression ratio and 6-liter size. The hipo LQ9 has 10:1 compression, which doesn’t allow for as much boost and timing, so the improvement isn’t as impressive. The 4.8- and 5.3-liter engines all have 9.5:1 compression, so they make good power under boost — they just don’t have the same displacement as the LQ4.
The supercharger/intake combo bolts on just like the stock intake, and the front drive installs quickly. Probably the only thing that is not intuitive in the installation is how to get the fuel injector wiring and a few other sensors and connectors released — those steps are shown here and in Chapter 4. Before removing the intake manifold, vacuum the top of the engine with a powerful vacuum to remove any dirt and debris that would otherwise fall in to the exposed intake ports of the engine.
Actually, as a testimony to the engineering work that went into the MagnaCharger system, getting the stock wiring reinstalled and wiring up the added Magnuson components takes longer than the mechanical installation work — that’s how simple it is to install the hard parts.
The supercharger comes with a 3.3- inch-diameter pulley from Magnuson, but there are a plethora of pulley diameters available. Going to a smaller pulley spins the blower more and increases the amount of air entering the engine at any given time. Usually, if you do this you’re going to need some calibration work done beyond the calibration that MagnaCharger provides. This points out what might be considered the negative to the MagnaCharger system—it is not intended for big power engine combos. This means if you want more than 10 psi whistling in to the intake, or anywhere close to this, the MagnaCharger system really isn’t the system for you. This system is intended to operate on a stock engine with boost pressures less than 5 psi. But, after looking at the dyno figures, you’re probably wondering why anyone would want to spin this blower harder since it is already making over 500 ft-lb of torque and 500 hp!
LS6 Parts for Power
The commonality of the Gen III architecture really is shown right here. Adding certain components originally developed for the special performance LS6 engine in the Z06 Corvette to any Vortec truck engine can provide up to 40 more horsepower with no other mechanical modifications.
What’s impressive about this is that it’s using all components manufactured by GM. They have GM part numbers. They all bolt on to the 4.8-, 5.3-, and 6.0- liter engines with no modifications to the basic architecture (which makes sense, as the architecture is common). Yet, they provide a real performance improvement. Now there are some good reasons for checking out this plan of action.
On the 6.0-Liter
The LQ4 and LQ9 aluminum cylinder heads have 72-cc combustion chambers, while the LS6 combustion chambers are 64 cc. The 8-cc decrease in chamber volume results in an increase in mechanical compression ratio of about 1 full point (from 10:1 to 11:1). Usually, increasing the compression one point with a performance engine would result in detonation that would damage the engine if it ran on anything but premium fuel. But again, almost all of the Gen III V-8 truck engines were originally designed to operate with regular 87-octane gasoline; as far as I know, only the hi-po 345-hp LQ9 was designed for premium. So, on most truck engines, the new compression ratio can be accommodated by using premium 92-octane gasoline. For some extra power, you can also install the LS6 camshaft. This cam, with its extra duration, will make more high-RPM power and bleed off some of the static compression at low RPM, giving you a little extra cushion against detonation.
Unlike the cars, the Gen III V-8 is not mounted halfway under the windshield on the full-size trucks. This means you could make the cam and head swap in the trucks without being a contortionist. To make the job easier, it’s a good idea to remove the hood. Also, the radiator will need to be removed, along with the grille. Then you’ll be able to slide the cam forward enough to remove it from the engine. The grille is straightforward enough you can figure it out as you go, but the hood and some other component removal procedures are covered in Chapter 4.
The cam swap is actually a neat process on the Gen III V-8. If you aren’t swapping the heads, the cam can be changed without removing them, the valley plate, or the intake manifold. The swap can be performed this way because the lifters ride in plastic retainers that will hold them up at the top of their lift for a short amount of time if the pushrods have been removed. This makes swapping cams on the Gen III a really fast process.
First, spin the engine over until the number-1 cylinder is at top dead center (TDC). This is done to line up the timing gear ‘dots’ before tearing the engine apart if you are going to make this swap without pulling the heads. This helps you avoid having to turn the engine over in minute increments with compression in all the cylinders to find TDC when reinstalling the cam. Then, simply loosen the rockers, pull out the pushrods, spin the cam 360 degrees, remove the bolts holding the upper timing gear and cam retention plate in place, and pull out the cam.
No matter what cam you are swapping and how knowledgeable your source of valve-to-piston clearance info is, you should always check it yourself just to be sure. Valve/piston contact is a catastrophe that’ll require considerable work and money to replace bent/broken valves, bashed up cylinder heads, broken pistons, and sometimes a broken engine block if you’re really lucky.
To check valve-to-piston clearance properly, refer to the process detailed in Chapter 6. If the clearance between the valves and pistons is less than 0.160 inch, you may have to cut reliefs in the pistons. Another possible solution is to increase the head gasket thickness (probably not that great of an idea, as it will increase combustion chamber volume and decrease combustion ratio, which will reduce power). Or you could change the advance or retard of the camshaft to move maximum valve lift (which will also affect power), or change the cam altogether.
If you swap the ’02 LS6 cam into a Vortec engine and put in a longer, stronger pushrod to correct for the smaller base circle on the ’02 LS6 cam and get back to good valvetrain geometry, there should be no problems. Even with that said, though, it’s a good idea to check everything to make sure there are no valve-to-piston clearances, valvetrain wear, or other issues that might ruin a good running engine.
Well, what can you say other than all hail Jim Hicks? He is the GM engineer that led the team that created the LS6 cam. To say they are fantastic would be an understatement. It seems whatever Gen III V-8 engine this cam is slid in, about 40 hp comes barreling out. Then, add in some freer breathing equipment on the inlet and exhaust side, and maybe some increased compression and whoa, at least another 10 or 15 hp rolls out. In case you don’t know, 50 hp can be felt in the seat of your pants and it feels good.
On the 5.3-Liter
The 5.3-liter Gen III Vortec V-8 is probably the most common Gen III engine sold by GM (having been built in a 2:1 ratio to any other Gen III V-8), we have provided a full host of dyno tests adding various components to the base engine. You’ll probably notice there is not a dyno test with LS6 heads bolted to the base 5.3-liter engine. Well, this test was run, but since the engine lost power, it wasn’t included in the rundown.
The reason the engine lost power can probably be traced to the change in compression ratio, as the 5.3-liter heads have 61.1-cc combustion chambers and the LS6 heads have 64-cc chambers. While this might not seem like a lot, it’s enough to eliminate the potential power increase from the larger ports and improved flow of the LS6 heads. Milling the deck surface on the heads, or using the milled GMPP CNC-ported LS6 heads, would probably show a gain, but due to time constraints, that test was not run.
Just looking at how well the LS6 cam did in the 5.3- and 6.0-liter should be enough for most enthusiasts. On both engines, while peak power was slightly raised in the powerband, each engine made about 40 more horsepower just by swapping in the Z06 cam! Add in a few aftermarket components if you wish and the power can be raised another 10 to 20 hp. Not bad for a day’s work.
The word alone sounds sexy. Up until recently, there haven’t been any turbo kits for the truck Gen III V-8 engines. But now Wheel to Wheel Powertrain (W2W) offers a turbo kit designed to bolt on to a stock 4.8-, 5.3-, or 6.0-liter Gen III V-8 engine and help it make considerably more power than GM ever imagined.
After reading any of the previous chapters in this book, you know that making power in the 600 horsepower range is asking a lot of the stock short block. While this is true, turbos in general are much more “kind” to internal combustion components than high compression, naturally aspirated combinations, or power adders like superchargers or nitrous oxide. This is because most turbo applications are very linear in their increase and decrease in cylinder pressure, which means there are few pressure or temperature spikes during engine operation that might lead to detonation of preignition that could damage a piston or other parts. Also, with electronic controls on the fuel and especially the spark advance, turbo systems today can be monitored very closely to make sure the engine doesn’t run lean or detonate the pistons into submission.
The W2W kit comes with all the tubing, turbo, intercooler, calibration, and other necessary components.
Usually, turbo systems have a very high cost because of the tubing, intercooler, and other ancillary components needed to create the turbo system. In this case, W2W uses the stock exhaust manifolds but flips them 180 degrees so the outlets are pointing up. This eliminates one of the most expensive components on a turbo system — the tube headers. W2W creates all the tubing required to hook up the turbo to the exhaust and intercooler and then to the inlet, which eliminates the second most expensive component set on a turbo system — the custom headers.
The Garrett turbo used here has a 67- mm inlet to match the size of the engine. A set of Delphi 42-lb/hr injectors are swapped into the intake manifold to provide increased fuel flow to the more powerful turbocharged engine.
W2W recommends replacing the exhaust system with a less restrictive one so there will be less backpressure to prohibit the turbo from spooling up. The stock catalytic converters are one of the real problems. They’ll melt into one solid glob if you try to run them with this turbo motor. This might sound comical, but the resulting infinite backpressure can cause some grim damage to the engine and turbo components. Aftermarket high-flow catalysts are required.
The kit bolts on without any changes required to the engine itself. W2W provides all the tubing and mounting components, and the kit uses the stock exhaust manifolds. Calibration work will be required to alter the fuel and spark tables, and more importantly, the transmission controls, to handle the newly found power. If you vary from the W2W kit, you’ll need some specialized calibration work, as there is considerable detail in getting this type of system to work smoothly and reliably.
W2W built a few early versions of this kit with forged cranks, rods, and pistons of stock dimensions in 6.0-liter blocks to determine what kind of power the engine could take. As you can see by the dyno chart, this turbo package can make almost 900 hp without working too hard. Working backwards towards a stock engine combination, W2W was able to determine they could safely make over 600 hp on an otherwise stock 6.0-liter LQ4.
This is with stock pistons, stock rods, stock heads, and other stock components. This points out one of the impressive aspects of turbo systems. Just cranking up the boost can provide impressive returns on power — you just need to have internal components that can handle the increased boost. A stock 2004 4.8-liter Gen III V-8 makes peak power of 290 ft-lbs of torque at 4,000 rpm and 285 hp at 5,600 rpm, so you can see the turbo motor is making almost double those numbers without a single change to the engine. but the fuse is much shorter on the internal components at those power levels.
Written by Will Handzel and Posted with Permission of CarTechBooks