340 HP    435 Torque          $4100.00

DESCRIPTION: HT 383 BASE ENGINE
There comes a time when you may not just want more power, you may need more power. Times like when you are towing your show car or bass boat with that 1970s-and-earlier GM truck, and it just doesn't have the low-end grunt that you need to flatten hills or make a safe pass. For those times, our engineers designed the HT (high torque) 383 with lots of cubic inches and other components to enhance the low-rpm power that you need. The GM Performance Parts HT383 has been specifically engineered for low-rpm torque, and it's packed with durable parts that are all brand new. It produces 435 lb.-ft. of torque at 4000 rpm, but more importantly, it produces more than 400 lb.-ft. of weight-moving torque from 2500 rpm all the way up to its 4000 rpm peak. In other words, your trailer's worth of weekend fun is barely noticeable when hooked to a vehicle equipped with the HT383. The bottom end has a 383 stroker forged steel crankshaft, heavy-duty rods, and hypereutectic pistons. The block is cast iron with 4-bolt main caps, and's up to the task of making lots of power for years to come. The brand new HT383 makes a great alternative to salvage and rebuilt engines. Once installed, the HT383 makes it possible to look forward to that big hill or long haul. Don't just drive to your favorite fishing hole, be the first one there!

425 HP    460 Torque           $4925.00

DESCRIPTION:ZZ383/425 Crate Engine
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 or off road powerhouse.
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 9.1 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: 1 3/4" primaries, 33 inches long with 4-inch collectors.
GM dual plane intake P/N 12366573 may be used for hood clearance on the ZZ383/425, but results in a decrease in peak horsepower of approximately 15-20 horsepower.