It seems that lately everybody thinks we should all be satisfied to make 400 hp on 92 octane with a Chevy 350. That's great if you think 400 ponies is a lot of power. But the pace of development in cams, heads, and carbs has made it easy and affordable to go beyond that level of performance. For this project, we wanted to go way past it while still maintaining pump-gas and basic bolt-together parts compatibility. Our goal was 500 hp using off-the-shelf parts with no machine work required.
Here's the basic recipe: a GM Performance Parts' ZZ4 partial engine assembly, which comes with a forged crank, four-bolt-main caps, and high-silicon aluminum pistons for about $1,700. Then grab a Comp Cams Xtreme Energy mechanical roller cam, Air Flow Research's superlative 195 Street Head, a tried-and-true Edelbrock Victor Jr. intake with a Speed Demon carb, an HEI, and 13⁄4-inch headers and throw it all on the engine.
Assembling this engine isn't a total slam dunk, however. The solid-roller cam we picked is big enough that piston-to-valve clearance needs to be checked, standard-length pushrods will probably be too short, and there's potential for rocker-arm- to-valvespring retainer and retainer-to-valveguide or -seal interference. In short, everything has to be checked, and (if necessary) corrected.
In this case, Comp's Xtreme Energy XR280R cam was slightly milder than the grind we originally intended to use (the next larger cam actually hit the factory pistons' shallow valve notches). Comp Hi-Tech pushrods (PN 7994) were 0.050-inch longer than standard and were needed to achieve proper valvetrain geometry, and the AFR head's supplied valvesprings required shims to achieve the necessary valvespring pressure. Because we ordered the wrong style cam for this late-model roller-style block (see caption), the front cam thrust-plate retainer boss required trimming to clear the early upper double-roller cam sprocket (which in turn was needed to mate with the early-style front cam nose on Comp's mechanical roller cam).
Edelbrock's Victor Jr. single-plane intake (PN 2975) was chosen to maximize top-end power. | 
GM's 8-inch harmonic damper (PN 12555879) prevents bad vibes. |
The engine ran best with a Speed Demon 850-cfm double-pumper carb on a Wilson 1-inch open spacer. Jetting was "square," with No. 92s on all four corners. A 750 proved too restrictive. | |