ATK HP55C-EFI Chevy 383CI with Fitech EFI 500HP

A Fitech Go EFI 4 600HP throttle-body system, complete with its own handheld tuner, fuels this 500-hp, 505-lb-ft 383 stroker instead of the mechanical-secondary carburetor ATK uses on its other street-strip 383 builds.

The engine underneath the EFI

Strip away the fuel system and this is the same hardware as ATK's carbureted 500-hp stroker: the Dart SHP aluminum castings, 72cc chambers, 2.02/1.60 valve sizing, a forged 4340 Scat crankshaft turning matching Scat H-beam rods, and 10.2:1-compression forged pistons. The Edelbrock Performer RPM Air-Gap intake, distributor, and water pump are mounted, with the Fitech throttle body, wiring harness, and handheld controller in place of a carburetor.

Fuel system notes

• This kit does not come with a fuel pump.
• An electric fuel pump works, and so does a mechanical pump if it runs through Fitech's Fuel Command Center.
• Idle quality takes after ATK's other street-strip 383 engines: expect a noticeably lopey idle from this cam.

Common questions

Can I tune this myself without a laptop? Fitech's system includes a handheld controller for adjusting fuel curves on the fly.

Does the kit supply its own fuel pump? No, that part is on you: an electric pump works, or a mechanical one routed through Fitech's Fuel Command Center hardware.

What octane does it need? ATK specifies 91 octane or higher for this compression ratio. California requires BAR compliance for engine swap installations.