Working on my wife's car. 86 mustang with a very mild 347 SBF and a 750HO carb from AED on pump gas. This is a high 8 second 1/8th mile car that my wife is getting her feet wet in the street class with so nothing special going on here. The engine starts, idles and takes throttle fine except when trying to footbrake the car at the track (what it was built for).

2000rpm launch, stab the throttle, the car initially accelerates for a split second, then burbles and stumbles, then takes off again. I've gone WAAY up on the squirters (31/35 to 44/42) which has helped, but not resolved the issue. I have also gone up and down on the idle air bleed (hi speed is not adjustable) only making it worse.

AED insists there is something else wrong with the engine build or that there is a converter issue. Engine is brand new, 3600rpm TCI converter, 3.73 gear etc.

Have tried a couple different timing curves in the distributor (18/36 and 26/36) with zero improvement. Have also tried leaving at different speeds with no change.

Have adjusted idle speed and verified transfer slots are not overly exposed on both primary and secondary. Have run with a slightly rich idle mixture as well as slightly lean. No change. Also went smaller on the squirters which made it way worse. Accelerator pump linkages are adjust properly.

Sure seems like there is a lean hole in the carb calibration but again, AED insists it can't be the carb and I need to look elsewhere.

I'm running out of places to look so looking for some ideas.

I'm trying to find another carb to test which will be one of the next steps as well as running the distributor with locked out timing advance.

This message has been edited. Last edited by: CSRacing,

Maybe a different accelerator pump cam with a longer duration? With more fuel going in with the bigger squirters helping, I'm thinking a longer duration shot could also help? No carb guru here, but I was reminded recently of accelerator pump cam differences by a friend.