Fast355

It really depends on the setup. I have seen LT1 builds want as much as 38* on pump gas at 12:1 compression.

I am sure my 383 would want more timing on pump gas if it were not pulling around a 7,000 lbs Express van with a 4L85E and only a 3.73 gear. 6L90E swap coming soon though. I bet it wants a little more timing when the engine is not under as much load.

CamOnlyJabroni

Agreed. Mine sees between 38-40 on E85 with 12.7:1. Probably isn't gaining much at 40 compared to 38 but the plugs still look good.

T/A KID

iTrader: (12)

I’ve NEVER seen an lt1 engine want less then 30 degrees at WOT even with 11.5 CR or more.. these old school design heads need timing

Fast355

Typically 34-38 is where I see LT1s and LT4s make peak power. I have seen a couple that are knock limited to around 32-34, but that is not the normal. One of the knock limiteds was an iron headed LT1 in an 85 Suburban. The other was an aluminum head 383 in a heavy Fleetwood.