With GM’s legendary Fast Burn cylinder heads and 383 cubic inches, the ZZ383/425 delivers incredible torque with smooth, linear delivery. If you're looking for a small-block package that delivers big-block power, then you’ve found it. 425 horsepower at an incredibly low 5400 RPM, and 460 ft.lbs. of torque at 4500 RPM make this the ideal hot street engine.

The excellent air handling and combustion characteristics of the Fast Burn cylinder heads combined with the ZZ383/425’s 3.800" stroke, make this engine the benchmark against which all other 383 inch small-blocks should be measured. And it’s tough, too. The 4340 nitrided and induction hardened crank and unique forged PM rods see to that. The 9.7 to 1 compression ratio ensures that the ZZ383/425 is 92 octane pump gas friendly.

The ZZ383/425 gets a stout .509/.528 lift steel camshaft with 222/230 duration at .050 lift. Hydraulic roller lifters and GM’s time tested 1.5 to 1 roller rocker arms round out the valve train. And, of course, it has the Fast Burn head’s lightweight stainless steel valves and retainers for reliable performance at extended RPM.

GM’s testing was completed using a GM single plane intake, P/N 12496822 and a 750 CFM Demon carburetor with mechanical secondaries. Test header specs are: 13/4" primaries, 33 inches long with a 4-inch collectors. GM dual plane intake P/N 12366573 may be used for hood clearance on the ZZ383/425, but it results in a decrease in peak horsepower of approximately 15-20 horsepower.