The ZZ6: A New Crate Engine on the 60th Anniversary of the Small-Block

About twenty-five years ago the era of modern crate engines began with General Motors (GM) release of the “H.O. 350,” an all-new, high-performance small-block engine assembly that blended the best of old and new technologies through the use of hydraulic-roller cams and aluminum cylinder-heads. For perhaps the first time, the “ZZZ” stamped blocks made it as cost-effective to buy a fully assembled crate engine as to build an equivalent engine from speed shop parts. In 1990, those first ZZZ crate engines had four-bolt mains, a forged one-piece rear main seal crankshaft, L98 Corvette aluminum cylinder heads, and a 9.8:1 compression ratio that produced 345 hp at 5,600 rpm and 370 lb-ft of torque at 3,600.

The early ZZZ engines were soon followed by ZZ1- and ZZ2- designated crate engines, although the power and torque ratings remained about the same. In 1992, the ZZ3 was introduced with the same peak power and torque numbers, but the power came on at lower rpm (345 hp at 5,250 rpm, 387 lb-ft at 3,250 rpm). The ZZ4 version of GM’s crate engine appeared in 1996 and became the longest-running ZZ engine with production all the way through 2014. Official power ratings for the ZZ4 were 355 hp and 418 lb-ft. In 2014, the ZZ5 was introduced and it made use of larger intake runners and larger valves to produce 400 hp and 400 lb-ft. of torque.

Fast forward to 2015 and Chevrolet has announced it will soon replace the ZZ5 with a new ZZ6 crate engine in 2016, the year that also happens to be the 60th Anniversary of the GM’s venerable small-block family of engines. The new ZZ6 crate engine will employ updated Fast Burn cylinder heads along with beehive-style valve springs to enhance high-rpm capabilities. The main differences from the ZZ5 include a larger, 770-cfm Holley carb, 1.5:1 roller rocker arms, and a single-plane intake manifold. The official power ratings from GM for the new ZZ6 are 405 hp at 5,600 rpm and 405 lb-ft of torque at 4,600, making it one of the most powerful 350 small block-based crate engines in the ZZ lineage.

To support high-rpm airflow and low-speed drivability, the ZZ6 engine employs 2.00/1.55-inch valves and uses a hydraulic roller camshaft with .474/.510-inch lift and 208/221-degrees duration. A forged steel crankshaft and high-silicon aluminum pistons in a four-bolt-main cast iron block complete the package. GM says the ZZ6 crate engine will be offered in two versions. The Base kit (P/N 19351532) includes a single-plane aluminum intake, distributor, water pump, damper and flexplate, the carburetor and other accessories are not included. The more complete Turn Key kit (P/N 19351533) includes the carburetor, air cleaner, starter, distributor, alternator, air conditioning compressor and front-end accessory drive system.

The ZZ crate engines have a proven reputation for power and durability, and the new ZZ6 looks like a pretty impressive package for a carbureted 5.7L. It would probably make a great motor for a non-numbers matching car or other restoration project, and we probably won’t have to wait too long to see how that turns out.

The availability of both engine kits will be announced at the SEMA Chevrolet Press Conference on November 3, 2015. For more information, log on to the Chevrolet Performance website at www.chevrolet.com/performance.html.

ZZ6 Crate Engine Specs

Advertised Horsepower – 405 hp @ 5,600rpm
Advertised Torque – 405 lb-ft @ 4,600rpm
Engine Type – Chevy Small-Block
Bore x Stroke – 4.000” x 3.48”
Block – Cast Iron with 4-bolt Mains
Crankshaft – Forged Steel
Connecting Rods – Forged Powder Metal
Pistons – Hypereutectic Aluminum
Intake Manifold – Single-Plane Aluminum
Carburetor – 770 cfm Holley
Camshaft – Steel Hydraulic Roller
Valve Lift – .474 intake/.510 exhaust
Camshaft Duration (@.050 in) – 208 degrees intake/221 degrees exhaust
Cylinder Heads – Fast Burn Aluminum – 62cc chambers
Valve Size – 2.000 intake/ 1.550 exhaust
Compression Ratio – 9.72:1 nominal
Rocker Arms – Aluminum roller style
Rocker Arm Ratio – 1.5:1
Recommended Fuel – 93 octane premium pump
Distributor – HEI
Ignition timing – 36 degrees @ 4,000rpm
Maximum Recommended RPM – 5,800rpm
Balance – External