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How Many Engines Have Been In The ZZZ Family?
Over the years, there have been seven ZZ engines. GM Performance referred to the new motor with the internal distinction of the “H.O. 350” label but stamped with the initials “ZZZ” to designate their engine code. (It is located on the block near the front passenger cylinder head).
The ZZZ Engine
In 1989, GM released its first fully “crate” engine, the ZZZ. The original motor had a cast iron block with aluminum cylinder heads from the L98 Corvette, four-bolt mains, and a forged one-piece rear main seal steel crankshaft. The hydraulic roller camshaft turned via a timing chain, with forged connecting rods scavenged from the Corvette Z28/LTI engines used during the 70s. An dual-plane intake (high-rise) manifold was designed for a stock four-barrel Holley Carburetor. The carb and intake provided an efficient and unobstructed flow of air, which gave the engine an incredible performance level. The result was a stone-cold, reliable engine that produced strong power through the entire rpm level.
The engine produced a 9.8:1 compression, resulting in 345 hp and 370 lb-ft of torque. While they weren’t cheap (around $2,500), you could purchase the complete engine from several performance Chevy dealers. The engines were an instant success because they saved time and money for hotrodders who wanted to just slap a new motor into a car’s engine bay without having to take the time to rebuild one from scratch.
ZZ1 and ZZ2
GM Performance recognized that the “crate” engines were selling so well, but the only complaint was that the ZZZ engine had a cold piston slap from using non-offset wrist pin pistons. The issue was corrected early on in the redesigned ZZ1 and ZZ2, but other changes were made, such as the new “butt-link chain” replaced the roller chain (along with a few other minor modifications). The same power outputs were carried over, as both engines were essentially carbon copies of the original ZZZ engine.
ZZ3
In late 1992, the ZZ motors received significant changes by reintroducing the roller chain and utilizing a lower-rise intake manifold that accepted a Rochester quad-jet to allow for more hood clearance. A new dual hydraulic roller camshaft system helped provide slightly better torque, necessitating new valve seats, lighter valve-spring retainers, and seals to make them compatible. Power levels and compression ratios were retained, but the cost of the engines also began to creep up.
ZZ4
While we will get into the specifics of the ZZ4 below, when the ZZ4 was released in 1996, the engine benefited from the Gen II small block LT1. With upgraded pistons and rings, the compression ratio was bumped to 10.1:1. The power outputs varied, but most common ZZ4 engines produce 355 hp and 418 lb-ft of torque. The ZZ4 was the longest-running engine in the ZZ series, with a run up to 2014.
The ZZ4 retained the cast iron block, aluminum heads, and a hydraulic roller camshaft. From 2004, Chevrolet began to offer the crate engine as a ZZ4 350 turn-key crate engine, which included new spark plug wires, and everything else that might be needed. (The turn-key made the final assembly process much more manageable). The ZZ4 remains a popular engine upgrade for many classic car restorers.
ZZ5 And ZZ6
In 2014, the ZZ5 was released with upgraded components based on the LT4 and Vortec engines. New GM fast-burn aluminum heads were installed (dumping the older aluminum heads from the L98), but the modification required more robust high-velocity intake runners and larger valves. Despite using the same Mahle pistons as the ZZ4, the new heads lowered the compression. Even though overall power numbers increased to 400 hp, the torque dropped slightly. In 2016, the ZZ6 appeared, which increased the engine’s performance to 405 hp and 405 lb-ft of torque.
The Performance Analysis of the ZZ4 Crate Engine?
The ZZ4 has been the most famous member of the ZZ family of “crate” engines that GM has offered, but it has been discontinued. There are crate engines based on the ZZ4 that use fast burn cylinder heads (as were used in ZZ5 and ZZ6 engines) and other modifications. If you are lucky enough to find an intact ZZ4 “turnkey” engine (like this one we found while searching on thirdgenranch.com), expect to pay a pretty penny.
The engine has a reputation for being a reliable performer and is best suited to pre-1977 classic cars that are not meant to be pushed hard. The ZZ4 crate engines come with new spark plug wires, a cast iron block, aluminum heads, a steel crankshaft, and a hydraulic roller-style camshaft/lifters. With the stock intake, large valves and other components, the ZZ4 350 turn key can promote efficient performance and be a nice addition to the restoration project for any street rod.
As a general rule, the engine makes adequate power ratios for everyday driving, and if that is what you are looking for, then the ZZ4 might be the best choice. One thing that appeals to some Chevy owners is how easily the ZZ4 takes to performance upgrades (many bolt-on applications can generate significant boosts).
Now, don’t get us wrong. The ZZ4 is a good engine with a sturdy base, and many gearheads have adapted it to their needs over the years. (Always read the fine print on any turn-key engine to discover the things that might affect engine warranty). However, there are some issues with the engine's internals that you should consider upgrading if you plan to push the engine to significant power and performance levels.
WeaK Push Rods
Many forums concerning the ZZ4 indicate that the pushrods tend to be weak, and boosting your engine can often create too much stress, resulting in bent rods. (This is never a good thing). Bent push rods can create severe issues if left untreated.
While there is a great deal of debate on what might be the cause, there is a general consensus that the stock ZZ4 push rods are just not as good as many aftermarket rods available. The push rod length is 7.2 inches, and we recommend using a COMP 7702 Hi-Tech Pushrod Checker when doing this modification.
Lazy Camshaft
The ZZ4 uses a hydraulic roller camshaft that was brought over from the previous ZZ3 motor. The standard upgrade is to an LT4 Hot Cams with a gross lift of 0.525 and 1.6:1 RRs. Most forums report that replacing the camshaft can push the valve springs to their limits. (Don’t fret. The ZZ4 and the LT4 use the same valve springs to handle the load. If you don’t trust them or they’ve gone bad, you should change them out).
Best With Premium Gas
The ZZ4 is a GM performance engine, and as such, it requires a higher-octane fuel to perform at its best. The engine will run nominally on regular 87 octane, but most owners agree that Premium gasoline is best (especially to reduce any knocking or pinging).
