Mudslinging

My 79 D100 pick up with a 318 and holley 650 backs fires when I accelerate hard. When I drive normal it doesn't do it. It does it for a while then it doesn't do it for a while. Could it be carburator or timing? Any imput will be appreciate.

mikerp76

is it backfiring out the carb or the exhaust?

Mudslinging

I feel it in the exhaust. Its weird, it was doing it a lot when I step on it, it would back fire bad, as soon as I back off on the accelerator it would go away, then it stopped doing it for a while. Now started back up again. It almost feels like, when the secondaries open up, that is when the back firing starts. On a side note, a couple of times I had problems with the secondaries staying wide open and had to shut the truck off to giggle the mechanism that the secondaries sit on to get them to close. So I was thinking carburetor.

mikerp76

it could be getting too much fuel which could cause the problem

Mudslinging

Thanks mike76, I will send the carb for rebuilding. Do you have any place in particular that rebuild carbs.

78D200

Sounds like too much fuel and your timing may need to be advanced a degree or two.

Gorts 5th

if he s getin a back fire out the tail pipe its to advanced the.. timing. what might be happening is your vacuum is hooked up to a port that is advancing it to quickly and causing the tail pipe back fire but also if your secondaries are sticking open thats a red flag for a bad or incorrectly modified carb could be all your problems you have a few things to check

mikerp76

i know you can get a carb kit from any aouto paarts sorte in your area. as for who could rebuild it for you i would call around some of your local shops or try to find out if one ofour members here know how to do it that may live close by. i do all the carb work on my car myself. it's not that complicated as it may seem. just be sure to take your time and tey to remember what went where.