backfireing

ive got a 77 c10 with a 350. About a week ago it started backfiring through the carb i pulled the carb off and the gasket underneith was blownout so i replaced it hopeing that that would fix it but it didn't. I think it may be a valve sticking but it only backfires when you give it gas but not at idle. Does anybody have any ideas how to fix this? Thanks.

if you have not messed with wires, or distributer then you are probably right about valve problem, maybe worn timing chain but not sure

yeah i replaced all plugs and wires new distributor cap and rotor and even messed with the timing. I pulled the valve covers and the front rocker on the passenger side was way loose can i just tighten it up or will i ruin it? thanks

on a 77 i think you have a adjustment, (i think)there are 1/2 nut in center of rocker, these are locking nuts, they have indentations on the top to keep them from loosing up, if it is loose you should replace them. there is an adjustment sequence for tightening them, i am not totaly famileir with it, but it is consists of setting up on top deep center of no 1 compression stroke and adusting # 1 valves and ceartin other that are on low spot of cam, did this on 78 motor for ford, you twist push rod with fingers and tighten up nut intill you feel drag on pushrod then back off certain amount, after ajusting certian valves you rotate crank one revolution and due remainder. you should probably get replacement nuts and a manual or find the procedure and replace them all so you will not have this problem again.
sorry i can not help more
good luck

is your distrubtor still the original vacuum advance? Is the vacuum advance working. Pull the dist, or hook a long vacuum line to it. Suck on it and watch to see if the pin moves to advance timing, and then stick your toungue to it to see if it holds, If not your vacuum adv. could be the culprit. THat's what was wrong w/mine when mine would backfire out of the carb.

The reason the one rocker was loose could be a lobe on the cam going flat or a bent push-rod or bad lifter. I would try the other posters suggestions first I am just adding a worst case scenario that I have seen many times. I had one that drove fine on the highway and in town until you got on it a little and it backfired and sputtered. After checking everthing else it turned out to be the cam.

well i tightened the rocker and now it runs great. no backfire. Thanks or all the help. NOW i just gotta find that damn vacuum leak.