GM 350 CI ZZ4 Crate Engine Build - Hail The Gladiator

The Roman gladiator was a fierce warrior who would fight any enemy in any land and return to shower his emperor with captured booty.

Our story is about an engine that has come to be called the Gladiator for both its strength and endurance. The name itself was not actually chosen by its owner, rather it was bestowed by those who have spent years abusing it.

The Gladiator's lineage can be traced back to Memphis, Tennessee, the home of Comp Cams. The power gods at Comp wanted a test mule that could withstand years of dyno abuse without killing the budget. Westech Performance Group was called upon to develop and test such an engine, with Comp Cams backing the deal. As a foundation, Westech ordered a GM Performance Parts ZZ4 crate engine, which it felt would be up to the task with minimal modifications.

Building The Gladiator

GM's 350ci ZZ4 crate engine is a true street engine, designed to run on 92-octane pump gas all day and deliver reliable horsepower for years. Westech unwrapped the ZZ4 and immediately strapped it onto its Superflow 901 engine dyno for its first flogging. GM claims the ZZ4 will make a respectable 355 hp and 400 lb-ft of torque. This particular motor cranked out 349 hp at 5,400 rpm and squeaked by with 380 lb-ft at 4,100 (see Test 1). Not quite up to par in the torque department, but that could be attributed to the large 13/4-inch headers that Westech has used in all the Gladiator's testing.

With the power baseline established, it was time to start testing Comp Cams camshafts. Out came the GMPP hydraulic roller cam and in went a Comp Cams 268H hydraulic flat-tappet camshaft, which actually featured less lift and duration than the stock cam. On top went an Edelbrock Performer RPM intake manifold along with Comp Cams springs, retainers, pushrods, and Hi-Tech roller rockers. For fuel and spark Westech added a Holley 750 double-pumper carb and an MSD billet distributor and wires.

The new, smaller Comp Cams hydraulic camshaft didn't stop the Gladiator from cranking out a new peak of 380 hp at 5,400 rpm and 402 lb-ft at 4,100 rpm, a net increase of 31 hp and 21 lb-ft over stock (see Test 2). With these few simple changes making such a good power improvement, Westech couldn't resist adding some hard-core parts to this engine.

The Rebirth

The testing schedule called for more abuse, and Westech felt that a set of Speed-Pro forged pistons (PN L2256F) and file-fit moly rings would handle the task better than the cast factory slugs. Westech's John Baechtel and Steve Abruczese tore the ZZ4 apart and hung the new pistons and rings on the stock powdered-metal rods. They also used new Fel-Pro head gaskets (PN 1010) to keep the engine around 10:1 compression. With the new reciprocating pieces in place, Westech bolted on a pair of Air Flow Research CNC-ported 190cc street heads for the Gladiator to wear into battle. CHP has tested the AFR 190s (see "Flow to Go," Oct. '98) and found them to flow exceptionally well, and they must be recognized as a big contributing factor to the overall power the Gladiator made in its later stages.

A few more changes were made upon reassembly, all in the search of additional power. To start, Westech added a much larger Comp Cams 292H hydraulic flat-tappet camshaft along with an Edelbrock Victor Jr. intake manifold and a new Speed Demon 750-cfm carb. The Gladiator carried the same 13/4-inch headers and 3-inch exhaust armor into its next battle.

After consuming too many gallons of 92-octane pump gas to count and withstanding countless full-throttle dyno pulls, the Gladiator emerged from this battle victorious again, this time returning with a gift of 468 horses and 421 lb-ft of grunt (see Test 3). The new, better-breathing Gladiator gained its extra power up high in the rpm band, with its new horsepower peak arriving at 6,800 rpm and its new torque peak at 5,200.

The Ultimate Warrior

Then it was time to really test the Gladiator's mettle. Abruczese pulled out the 292H camshaft and replaced it with a custom-ground Comp Cams solid roller camshaft. This big cam featured 254 and 260 degrees duration at 0.050 with 0.583- and 0.589-inch valve lift on the intake and exhaust respectively. Comp ground the cam on a 110-degree lobe separation angle to keep power at a reasonable rpm. The only changes made to the Gladiator's external armor were a 2-inch carb spacer bolted on top of the Victor Jr. intake and a larger Demon 850 carb. Westech also changed the valvesprings and pushrods and deepened the valve-relief notches in the pistons to clear the almost 0.600-inch valve lift. With the engine sealed up, it was sent back into battle with the Superflow waterbrake. The fight was over quickly when the Gladiator emerged carrying 527 horses on its back.

What began as just a simple stock ZZ4 crate engine has since produced 527 hp and 459 lb-ft of torque (see Test 4), all with a few simple bolt-ons and new pistons and rings. To date, the Gladiator has withstood over 1,000 full-throttle dyno battles without a single injury and continues the fight today. Someday, the Gladiator will be laid to rest and its suit of armor retired, but until that day the potent warrior will continue to shine and prove its mettle.