Chevy 427 motor

[Dave King]

I"m tuning a Chevy 427 motor for the first time and I have it dialed in good for driveability. However the car seems to lack the seat of the pants torque as it can't spin the tires at all. Motor seems sound, cranking compression is good, burns the plugs fine, no signs of detonation, a/f 13.0 at WOT. Can anyone give me any advice for the timing curve? Right now I have a flat 18 degrees timing on it. Here's what the motor has.

427 Chevy Crate motor
Accel Intake
Edelbrock heads
12:1 pistons, compression is about 11.7:1
Runs on 93 octane

 

[gs462]

First off 93 octane seems WAY low for almost 12-1, hows the timing???

 

[Pablo]

Your compression is pretty high so proceed with caution, but 18 degrees is really no where near the amount of timing an N/A bbc is going to need at wot.

I have a lot of experience in SBCs and an SBC with modern aluminum heads typically wants low 30's timing wise with high compression. My iron headed (early 80's H.O. heads) 310 with 10:1 CR ran its best at 36 degrees.

The ramp and total timing can vary depending on the vehicle weight, gearing, aerodynamics, etc. A heavier vehicle wants a lazier timing curve, I.e. all in by 3400 rpm, a lighter vehicle can get away with topping out at 2800 rpm.

IIRC, BBC's typically need more timing lead than SBCs. Low timing will make an engine feel very soft. Also, are you sure you have 13.0:1 throughout the entire rpm range as verified by a wideband O2 sensor? If so, I would richen that up a bit to the 12.6-12.7 range. Hopefully you have a knock sensor you can monitor while you are tuning. That engine will probably run best on higher octane fuel, a good E85 candidate right there.

 

[Dusty Bradford]

Like they said, timing is about half of what it should be for a n/a motor. Even boosted BBC's need 36-38 down low. Raise it to 30 and go from there, listening for pinging.

 

[bobc455]

Do you have the knock sensor hooked up & enabled?

-Bob C.

 

["Turbo-T"]

Try setting the total timing for 36-38 degrees all in by 3000 rpm. That seems to be the magic sweet spot for a Chevy V8 engine.