ATK HP94M Chevy 383 Stroker Mid Dress Engine 415HP

Mid-dress means the HP94M, a 383 stroker making 415 hp and 460 lb-ft of torque, ships with the intake manifold, oil pan, timing cover, and harmonic balancer already in place, leaving the flexplate or flywheel for you to match to your transmission.

What is already on, what is not

A dual-plane intake and an HEI distributor come bolted on, though the carburetor is left to you; ATK suggests a Quick Fuel 680 CFM unit backed by a Holley mechanical pump good for 110 gallons per hour. Neither ships with this build, so add those plus your flexplate or flywheel before swap day.

Inside the stroker

4.040 inches of bore and 3.750 inches of stroke give this stroker its 383 cubic inches, on a Scat nodular iron crankshaft and Scat I-beam rods with ARP bolts. Roller rockers made of billet aluminum spin against ATK's aluminum heads, above hypereutectic pistons holding 9.7:1 compression, with timing handled by a double roller chain. ATK recommends 91 octane fuel for this combination.

Q: Does it come with a carburetor? No; ATK's recommendation is a 680 CFM unit, purchased separately.

Choosing mid-dress over the fully dressed version makes sense if you already own a flexplate or flywheel, or if you would rather pick your own carburetor and exhaust than accept ATK's recommendation for them. It also suits a swap where the transmission side of the build is already decided before the engine shows up.