Chevy L8P Crate engine & 6L80e Transmission in 71 Camaro

[Carlo C.]

What did it take to mate the 4l80 to the l8t? Are you doing a full manual 4l80? I can’t find any swap harnesses online for that combo.

Easytouring831,

GM Performance doesn’t offer a standalone controller that will properly run a 4L80 behind this setup, so something had to give. Cutting up the floor to cram in a 6-speed wasn’t happening. I wasn’t about to lose the factory console just to row gears. Deal breaker.

So the GM ECU and harness hit the bench, and in went a Holley Terminator X (Gen V LT Direct Injection kit, 550-1631). If it was going to run, shift, and behave like it should, Holley was going to be in charge.

Of course, nothing worth doing is ever plug-and-play.

Holley doesn’t currently support the factory L8P DBW throttle body, which sent me down the rabbit hole until I got Nick Williams — the throttle body guru — on the phone. After walking through a few checks, he nailed it: ditch the L8P throttle body and run a 2019 Corvette unit. It’s physically identical to the L8P throttle body, likely with different internal electronics, but with one key difference — it actually works with the Holley system.

I would also highly recommend getting the pedal assembly from GM as well.

And here’s the important part: buy it from GM. Not the parts store. Not aftermarket. GM.

We tried a locally sourced replacement first. It failed immediately.

The genuine GM unit? Bolted on, synced up, and worked exactly like it should. No drama.



Here’s what fixed it:

Throttle Body – GM #12669871

DBW Pedal – C6 Corvette, GM #19417903

Holley DBW Pedal Bracket – #145-131 (drops right into the factory pedal location)

Once everything was mounted and calibrated, it flat-out worked. Clean throttle response, no glitches, no guessing.

Sometimes the right answer isn’t the easy one — but when it fires up and does exactly what it’s supposed to, you know you made the right call.