popin threw the carb

[lytemup454]

ok guys i need some advice. my truck started poping threw the carb the other day and i'm not sure why. i had headers on there but they had a crack so i found some ram horn and went to the exhaust shop. once i left there the truck was running good and quiet. in running around town i burnt out the heat riser in the passenger manifold. i parked it, and pulled the manifold. I taped and plugged the hole then put it all back together. When i started it up and went to pull out of the drive way it started to back fire on me. i drove around the block but it didn't get any better, so i parked it.
I was able to to play with it a little today and found out it was poping threw the carb. I reved it up, and it back fired then shut off. I have no tuning experence what so ever. This is my first V8 and i only have about 30 miles on it.

sorry for the long post but i know you guys like to have all the info.


It's a sb 350 target master crate motor, HEI( skip white), 1406 carb. nothing fancy just something to drive. i don't know where the timing is at a local hot rodder played with it and said it was good it did run good untill now

What would cause this?????

[Cyclone44]

A valve that is stuck can cause this....

[lytemup454]

all of a sudden? what would cause it to stick?

[ChevLoRay]

If it is popping through the carburetor, the first thing that comes to my mind is timing.

What kind of carburetor does it have? If it is a Quadrajet, there's a possibility that fuel is leaking out of the the throttle body, into the intake manifold.

But, replacing headers with cast iron exhaust manifolds will make a difference, in my experience. With headers, you can run a richer mixture (which will create a hotter exhaust). My reasoning for this contention is based on experience, but I'm hoping that others will chime in and correct me if I am wrong. If my contention is correct, your mixture may be too rich and that could lead to the popping that may be dictated by the timing being wrong. I think headers may let you run more advance, and a richer mixture, since the headers dissipate heat that cast iron headers won't disperse.

[lytemup454]

so because my timing was set with the headers on it might of changed when i put in the manifolds? do i have this correct? it has a 1406 edlbrock. if anything i would say that the mixture was lean but it was running just fine.

[straitnate14]

kinda, your timming stayed the same but it might need to be changed with the new exaust, and the rich thing is because headers are able to flow more air and that leads to more fuel that can be pushed through the engine and when you went back to the ram horns you are putting in more fuel than the engine can burn and get rid of, Now does that sound about right?

[lytemup454]

so should i try and retard the timing?

[Somecallmejoe]

If it's a new engine check the valve lash. You may need to readjust the valves. You may have had a lifter that took a while to pump up and if it pumped up late you may have an intake valve hanging open. Also if you have an exhaust valve that is not opening will also cause it to pop through the carb. Thats were i would start after yu ch3eck your timing.

[vectorit]

Just chimin in on the obvious... Did your "hot rodder" buddy mess with the plugs? if he did, he might have switch the 5 and 7 plug wires... It will fire up, but will spit and pop like you describe. Are all the plug wires good? Havin headers are notorious for burning the wires causing shorts and bad engine performance. Vacuum leaks? is the Edlebrock mounted to a stock spread bore GM intake? or some other type? When I ran one of those I had to use a special square bore plate, and I was running a Edlebrock perfomer intake. With out it you will only have a sliver of gasket contact surface. If it slipped or dried up, then you will have a nasty vacuum leak causing some of the symptoms you described.

[Wrenchbender Ret]

I'm thinking you have some plug wires crossed or you bumped a plug & cracked it. Ive put in hundreds of the Goodwrench engines & have never had to adjust the valves. They run right out of the crate. Its got to be something you did when you changed manifolds unless you over reved it & threw off a rocker arm.

[lytemup454]

would cracked porcilin cause this?

[ChevLoRay]

If the porcelain on the plug is cracked, then the plug is broken. That plug may fire up, but under a load, it won't continue to function properly. The conductor contained within a spark plug is but a fraction of the overall diameter of the porcelain that you see. If the ceramic is cracked, the plug will (at best) fire intermittently under a load, but may idle without any problems.

[lytemup454]

well i barrowed a timing light today from a friend so i'll have to try that tomarrow morning