While the LS1 Gen III V-8...
While the LS1 Gen III V-8 is a great engine design, the real mind-numbing components are the cylinder heads. The symmetrical, cathedral intake ports are a result of massive amounts of experience, testing, and innovation. They were built out of necessity to fit between the pushrods, the four head bolts, and other systems but are impressive in their ability to flow air. The design is common between all the cars and trucks through 2005, which makes it easy to swap parts for power. These are GM Performance Parts CNC-ported cylinder heads that will yield additional power.
While the LS1 Gen III V-8 is a new pushrod engine, many of the systems will seem familiar once you start working on them-except for one. The calibration side of the Gen III is not for the faint of heart. The factory controls should be changed with caution. Some of the simple power programmers, like those available from Hypertech, DiabloSport, and others, limit the consumer's access and ability to make changes. This minimizes the chances of causing a problem with the drivetrain.
More advanced calibrating aids-most notably the systems available from LS1 Edit and HP Tuners-allow impressive access to the factory calibrations. But even simple changes to maximum engine rpm, transmission shift line pressures, and the ignition advance can quickly spell disaster. It is strongly suggested you find a reputable, recommended calibrator to assist in getting the correct calibration for your vehicle. Not only does a good calibration make a huge difference in power production, you will notice an improvement in driveability, longevity, and other aspects also.
In general, the Chevy LS1 Gen III V-8 is going to be the foundation for hot-rod engines for a long time to come-and for good reason. It was developed with the goal of being the best production pushrod V-8 ever built. Judging by the interest in the automotive enthusiast community, it is a fitting powerplant to celebrate the amazing 50-year legacy of the small-block engine.
If you are making any power...
If you are making any power increases to the Gen III V-8, plan on increasing the flow of oil through the engine with a mild porting of the oil outlet passage and with an increase in the pop-off valve pressure (here being accomplished with a shim under the spring). The LS1 Gen III was designed to operate on a minimum of oil to minimize power losses, so more power means you need more oil.
The information presented here applies to all Hummer H2s and Cadillac Escalades. Powered by the cast-iron block, aluminum-head, 300hp LQ4 6.0L Gen III V-8, these massive rolling statements become much more pleasurable to drive with just a few engine upgrades. Some of the simpler pieces include air inlet and after-cat exhausts, but for a real seat-of-the-pants power infusion, you'll need to bolt on a Magnuson supercharger for a sweet increase of at least 100 hp.
Of all the modifications you can make under that flip-forward hood, a supercharger is the most dramatic. Installing a blower on the LQ4 works great since the engine was built with a 9.41:1 compression ratio-so adding some sub-5-psi boost can be done without changing pistons or encountering engine-damaging detonation (but you must run premium fuel with the blower). The Magnuson unit seems to be the most popular because its system bolts on with minimum hassle and makes durable power.
The Gen III V-8 architecture was introduced to the public as the GM Regular Production Option (RPO) LS1 engine in the '97 Corvette. A GM engine RPO is essentially its name for that vehicle platform, but not its architecture name.
Because of the RPO confusion, the industry has ended up calling every variation of the Gen III V-8 an LS1, which is slightly incorrect.
Internally, GM calls this engine architecture the Gen III V-8, so that's what we're going to call it throughout this story. But as you've probably noticed, the story often references LS1s; that's because everyone in the business knows these engines as LS1s. Whatever you call them, the Gen III LS1 V-8-and the latest version that are being called Gen IVs-make great hot-rod engines, and you're going to be ready to jump into building one.
 If you install milled heads...  If you install milled heads or a smaller base circle cam (often required for more valve lift than stock) or make any changes to the top end of the engine, you'll need to correct the valvetrain geometry. The best way to do this is with different length aftermarket pushrods. This gets the geometry right but also adds strength since the factory pushrods are too lightweight for high-rpm valvespring pressures. So swapping them for performance pushrods is required anyway. |  When removing an engine from...  When removing an engine from a vehicle, it's important to limit how many systems you take apart. The coolant system will need to be drained, but the power steering and air conditioning can be left intact when removing the engine. This will minimize the special equipment and care required to get back to stock performance levels with these systems. |  While the mechanical side...  While the mechanical side of the Gen III LS1 V-8 is impressive in its simplicity, the electronic controls are complex and daunting to modify. GM did not intend for these systems to be accessed, but the aftermarket has figured out how to modify them and many calibrators are developing the means to operate these engines with performance equipment on them. |