squeek

Hey i have a 89 carburated 5.0. It has a 650 proform double pumper. when i start it up it pops back through the carb. no matter where i go if i try to get on it, it just stumbles and pops back through teh carb.

anybody know what this could be. jets is all i can think of but i have no clue what jets i should put in it?
thanks for any help

FuzzyDiceRule

sounds like your timing is off, not sure exactly what, but start there

projectresto83

Your timing. I had the same problem when I first got my carbed 306 up and going. Check your timing and reset it. If it still occurs and you know you have it dead on it sounds like your balancer is worn out and has spun on itself making your timing marks be in the wrong position.
Start your car and move your dizzy until it runs smooth and doesn't backfire anymore and not where that timing is. Then try and restab the dizzy to its correct spot and see if it does it again and then move the dizzy again until it is running smoothly. It will probably be in the same area.
I pulled out my dizzy and moved it a tooth one way and watched how it ran and then went the other direction and see if it was any better. After messing with it I realized that the balancer was wrong.
I pulled my timing cover off and double checked the timing marks on the chain were lined up to TDC and then installed my balancer and pointer and it was reading at like 30 degrees and it was set to zero.

SICNINETYCOUPE

back firing out the intake when the engine is cold is usually too far advanced timing and back firing out the exhaust is usually too far retarded timing, get a light on it and see what you find.