The most obvious question when you start studying the LSX block is, "What heads do you put on that thing?" After all, with six bolts per cylinder, there must be a head designed to take advantage of that additional feature. The answer is the new GM Performance Parts LSX-LS7 head--the first in a series of LSX heads coming from GM Performance Parts. While the LSX block will accept any LS-style cylinder head, the GM engineers took the already amazing LS7 head, beefed it up in key areas (valvespring perches, deck thickness, port walls, etc.) to take more abuse, and added the two additional fasteners per cylinder. The heads themselves are cast from 356-T6 aluminum and feature a ?-inch deck. That thick deck surface not only ensures a good gasket seal, but it also allows engine builders to develop their own custom combination of combustion chamber size and valve angle.

As installed in the LSX 454, the LSX-LS7 head is a study of pure efficiency. Flowing over 370 cfm on the intake--with the potential for a lot more if the end user so chooses--this head allows the LSX crate engine to feed 454 hungry cubic inches past the 6,500-rpm range. The LSX-LS7 head comes with 2.20-inch intake and 1.61-inch exhaust valves. The heads will work with either the newly released LSX-LS7 carbureted (PN 19166948) or LS7 (PN 12568976) intake manifolds. At launch time, the LSX 454 ships with the new LSX-LS7 intake and a carburetor (final selection was not defined at the time of this writing), and a fuel-injected version with the LS7 intake manifold is to follow.

The GMPP engineers didn't stop there. A complete new line of valvetrain components is also on the way. While GMPP has always had a good selection of cams, valvesprings, and cam kits, the new LSX camshaft as installed in the LSX 454 only hints at what's on the way. It's a "straight" design, with both intake and exhaust lifts measuring .635 inches, with 236 degrees intake/246 degrees exhaust duration (at .050-inch lift).

Those 454 inches come from an entirely new line of LSX engine components from GM Performance Parts. A forged steel crank (4.185-inch bore by 4.125-inch stroke) works with forged rods and 11:1 forged pistons to fill out the LSX block. These are all-new pieces designed from the ground up to deliver power and performance past what the production level of equipment allows. And, as GM's LSX trademark has come to signify, when you see "LSX" on a GM Performance Parts product, it represents only the finest materials, validation levels that only GM can reach, and horsepower potentials we've only dreamed about with such durability levels. It's an exciting time for GM fanatics and LS junkies alike.

Validation
It's hard to imagine the testing that a GM Performance Parts engine or engine component goes through. We won't spend much time going into all the gory details, but with a GM logo on the part, it gets thrashed to the limit before it goes public. GMPP has this insane validation study where an engine is kept at full load (a cycling of full throttle between peak horsepower and peak torque) for 50 hours. That's the equivalent of running 16,000 11-second dragstrip passes. It's for this reason that GMPP can easily back all of their stuff with a 2-year/50,000-mile warranty.

First Of Many LSX Crates
GMPP has got a killer new crate engine, and we'll see a bunch of new LSX parts coming out, but the real story is how nicely all of these components have been engineered to work together. The LSX 454 and its sibling, the LSX 376 (see sidebar, p. 76), are great examples of what this portfolio is going to be like. We are on the verge of having to completely readjust what we think of as "a lot of horsepower." After all, a small-block Chevy can only go so far before you start getting idle, starting, or fuel efficiency issues. These new LS engines--with a little nudge from the engineers at GM Performance Parts--are giving us levels of performance and efficiency that are hard to compare.