That Chevy LS1 small-block V-8 sitting under the hood isn't too bad, but, of course, it would be nice to make some power improvements. Ahead lie the tools and procedures that will make this possible: clarifying the terms used when talking about these engines, examining their architecture, and outlining several steps that can make that desire for more power a reality.
The Gen III V-8 was designed to be used in multiple cubic-inch sizes, to power cars and trucks, to be easy to manufacture and service, and to provide superior durability. It is a seemingly simple design that achieves all of these requirements with impressive power output and efficiency.
Some of the simple bolt-ons the LS1 Gen III V-8 makes power with include free-flowing airbox components (shown), after-cat exhaust systems, "wet" 100hp nitrous systems, mildly ported stock throttle bodies, a supercharger, and other similar components.
The Gen III small-block was designed from the beginning to be based on either an aluminum or cast-iron engine block. The cast-iron engine blocks came in the trucks, while the aluminum engines went in all the car applications with the thought that cast-iron blocks were needed to handle the rigors of truck usage. Some of the midsize SUVs and SSR trucks now use the aluminum block-based engines, but the fullsize trucks still use cast-iron blocks.
Here is the timeline of the first usages for this engine: The Regular Production Option (RPO), coded LS1, Gen III V-8 was introduced as an aluminum block-based engine in the '97 C5 Corvette. The aluminum block was improved and used as the foundation for the LS6 that powered the '01-'04 Corvette Z06s. The '98-'03 Camaro/Firebirds were powered by LS1s, as was the '04 GTO. The '04 Cadillac CTS-V started out with LS6 power.
The current engine in the '05 CTS-V, GTO, C6 Corvette, and SSR is the 400hp LS2 V-8-considered a Gen IV V-8 engine. The Gen IV is a variant of the Gen III. The Gen IV was not the completely new engine the Gen III was to the Gen I/II small-block V-8s, so much of this discussion applies to both the Gen III and IV V-8 engine families.
The Gen III aluminum block is a tour-de-force of technology. The block has pull-from-the-bottom head bolts, is deep-skirted, uses cross-bolted mains, has built-in crank and cam sensor mounts, and was designed to be as light as possible. The cylinder liners are thin, centrifugally cast, cast-iron inserts that are cast in place when the molten aluminum is poured into the mold. This reduces weight and machining time (not pressing in cylinder liners) and also extremely limits the amount the bores can be opened (because they are thin and are not perfectly positioned in the block). The LS1/LS6 engines come with 3.898-inch/99mm bores that can only be increased about 0.010 of an inch in diameter before fears of cutting through the liner become great.
One of the advantages of the just-released 6.0L Gen IV LS2 aluminum engine block is it has 4-inch/101.6mm bores and can be bored out 0.020 of an inch. Other than having bosses cast in place for the "Displacement on Demand" (DOD) in the lifter valley, the knock and cam sensors moved, and the head bolts being the short versions, the LS2 block is common with the LS1 block.