Update, I took my car in for a full tune up and everything look good to go. It hasn't backfired since that day so it must have been condensation from the car wash when I sprayed down the motor.
I belive i am having a simular problem with my motor. The thing will rev perfectly under gradual or even quick acceleration. If I slam the pedal to the floor though it will blow out the carb once then get up and go. I found the vac advance diaphragm was not holding so I replaced it and have been through and through the ign system to ensure everything is correct. I have 3 holes on my linkage to adust the pump throw and none seem to make a diff. It seemed to be spraying ok when the carb was apart, but I can't help but think some how its to blame.
The Jalopy Journal
