gswartz

Hey guys, first time poster here. I am having a problem with my 65 289 mustang. It was origionally a 2bbl that I converted over to a 4bbl. The car starts and rev's up fine but when ever you drop it into gear, AT, or let off the gas the car back fires and dies out. The first time I start it after a week or so the car just wants to back fire and die out. Anyone got any ideas. Its a 4100 carb number C5AF. It is not an origional mustang carb but is a 65 ford 4100 carb.

Thanks,
Greg

TBIAgent69

If it's backfiring out the intake, you have a vacuum leak or the mixture/jetting is too lean. If it's out the exhaust, check the timing (and vacuum advance), ensure the choke isn't stuck closed, and make sure it's not running too rich. Has the carb been rebuilt/cleaned recently?

edit to include:
If you want to look for a vacuum leak, spray carb cleaner on possible leak spots (base of carb, along intake manifold, etc) and see if it idles better. To check the vacuum advance, with the engine off disconnect the advance hose from the carb and suck on it. If you can keep sucking then it's bad.

Soaring

If it were mine, I'd go ahead and tune the engine. Start by timing it and adjusting the points. If that didn't do the trick, then check all your wires from the coil to dizzy to all the plug wires. If your spark is fine, then suspicion the fuel issues. Tune the carb for max air/fuel mixture, then check all the things stated above.