We then installed the lifter retention system and snapped the oil shield into the lifter valley. The oil shield keeps hot oil off of the bottom of the intake manifold. After this, we easily finished assembling the engine. Again, we were impressed at how everything needed-no matter how small-was included in the kit. GM really meant it when they called this kit "deluxe."

The easy and affordable solution to our valve cover clearance issue was found over at Spectre Performance in the form of these sweet fabricated aluminum pieces (PN 5041, $191.39). The 850 CFM Holley 4150 carb included in the ZZ502 kit has vacuum secondaries and an electric choke, which is ideal for street duty, and the Bow Tie intake is geared toward putting out gobs of low-end grunt.

This was also our first chance to try out COMP's new Ultra Pro Magnum rockers (PN 1620-16). We stuck with the same 1.7 ratio, but everything else about these new rockers are better than the stamped steel pieces included in the engine kit. Even though they are 8650 chrome-moly steel, they are still 5 percent lighter where it counts at the valve, compared to aluminum rockers. This is due to their web-like structure that adds strength where needed and reduces mass in low-stress areas.

Here's our finished and upgraded ZZ502 crate engine. The supplied aluminum Bow Tie dual-plane intake, Holley 850 CFM carb, harmonic damper, and HEI distributor top our long-block. Since our dyno uses an electric water pump, we didn't bother putting on the aluminum GM unit. We also found that the ZZ502 valve covers were just barely hitting our new COMP rockers. To clear, we would either have to double up the gasket or swap to a taller valve cover.

The ZZ502 is rated at 502 hp at 5,200 rpm and 567 lb-ft of torque at 4,200 rpm. After a little tuning, we nailed down 582 horses at 5,600 rpm and 594 lb-ft at 3,900. In addition to the gains of both torque and horsepower, we also liked how peak torque came on lower and how the 502 pulled farther than it did in stock form. Even if you account for some variance between GM's dyno and ours, that's a pretty decent gain.

Out of curiosity, we also decided to try a small 1-inch open spacer. Horsepower moved up a touch to 586 at 5,800 rpm while torque dropped to 589 lb-ft at 4,100 rpm. In essence, we traded a little low-end torque for a bit more horsepower on the top end. In a street car we would rather have the torque.

With both the Holley 1,000 CFM carb and the high-rise single-plane intake, we lost a ton of low-end power with almost no gain up top. The mill just wasn't able to hang in the upper rpm where a combo like this really comes on. But hey, it was worth a try. Considering the price of the carb and intake, the better "bang for the buck" is what GM supplied with the ZZ502 kit.

We then grabbed a Weiand single-plane high-rise intake off the shelf and slapped on a Holley 1,000 CFM carb. Before this we tried just the 1,000 CFM Holley carb (no spacer) on the GM intake and found almost no change with peaks of 588 hp and 595 lb-ft of torque.