ATK Engines ATK HP33M Chevy 383 Vortec Stroker Mid Dress Engine 390HP

The ATK HP33M pairs a 383 stroker bottom end with Dart Vortec-style cast-iron heads carrying 2.02/1.60 valves, for 390 hp and 460 lb-ft of torque out of a factory-style head casting rather than a big-port aluminum head. What mid-dress means here Underneath, Scat's nodular-iron crank turns I-beam rods secured with ARP 8740 bolts, under hypereutectic pistons at 9.5:1 compression. Ignition and the water side ship mounted: the distributor, water pump, and balancer are already in place, with the dual-plane intake bolted to the heads. What to check before you buy Because the timing here is set through the PCM rather than the distributor, your ECM calibration needs to match this cam and head combination. The oil pump is a Melling unit at standard volume, nothing upgraded for this combination. Fuel delivery is left to you: the carburetor and fuel pump are not mounted, only listed as ATK's suggested parts. Common questions Why Vortec-style heads on a stroker? ATK pairs this stroker rotating assembly with cast-iron heads instead of the larger aluminum heads used on its higher-output 383 builds. Is the ignition hardware in place? Yes, the distributor and water pump are mounted; what's missing is the spark plugs and plug wires, left as ATK's suggested parts. Why hypereutectic pistons instead of forged? ATK pairs the Vortec-style heads here with 9.5:1-compression hypereutectic pistons rather than the forged pistons used on its aluminum-headed 383s. California requires BAR compliance for engine swap installations.