getting frustrated, need some help.

[CHEVY_FOREVER]

I have a 82 GMC 1/2 ton 4x4. Got it under 6 mo ago. This truck is pretty solid, usual rust (rockers, botom of doors) and the engine ran pretty good even with a chopped up Holley. First thing we did was change the plugs, oil, headers and new exhaust. She ran pretty good just hated to start up and idle. Plus she also would stall out if you took you foot off when coming to a stop or just slowing down (not fun). After a few weeks of that I decided to put a Rochester Q-jet from summit racing. She ran pretty good wouldn't stall which was real nice (but lacked the power that was there with the Holley). I think it needs adjusted.

Anyway winter has been real cold this year and she has been running real rough on start up and takes a good 15 min of idling before she will go good. This is the first time with a carburated vehicle so I assumed that was norimal. Tried dry gas seemed to help some.

Next I will get to my real question at hand.

Recently out of no where she starts backfiring at start up and when idling, after 10 min it dies off and stops backfiring. However once I start down the road she runs pretty good and does not backfire untill I let off the gas then she starts shootiung up the neighborhood! Put a little gas on and it stops, take it off and boom! Anyone know what the heck is causing this? It sounds like it is coming from the exhaust and not the actual carb and i have looked for an exhaust leak and haven't found one. This is getting frustrating and am needing some help.....thanks.


Later.

[79BIG10]

For tuning the carb look here. http://www.73-87.com/garage/myqjet.htm

On the backfiring I would check out the carb and intake for a vaccum leak first. If you find one then you can fix that then tune the carb correctly without the leak causing a rich or lean condition.

[87 STEPPER]

Also check your timing if you haven't all ready