Racing Fuel Systems

I'm running a pair of 750s on a Holley Hi-Ram, on a Gen 3 Hemi. Motor goes clean on the brake, but when you let the button go, it rolls a little coal. Is there a way to lean out the fuel a little on the brake without effecting the curve down track? If the car is foot braked, the issue does not happen. Carb jetting is currently 72 on pass side with 6.5 pv, and 82 on drivers side. Plugs look decent after run.

When an engine misfires it can show a lean spike

I thought rolling coal meant black smoke from being excessively rich?

If you are running a launch rpm limit while on the trans-brake, typically you will see a lean condition during the rpm cut. To get a better understanding of where you are at...remove the rpm limiter, activate the brake, and load the motor up against the converter. See where the air fuel is at, with no rpm limiter. If you see clouds of carbon, that's typically a rich condition.

If you cannot roll it to the floor, and load up on the converter, motor coughs, stumbles, or dies....could be a carb related fuel issue with emulsion, pump shot, idle circuit, ect.

Timing of the event with a lazy curve, or lack of timing can cause launch problems as well.