CIS backfire
 

Removed engine and gearbox to fix clutch problem (broken fork) and when I put everything back in and started it again I will get a small backfire through the airbox when I try to raise the revs. Car starts fine so I think the airbox is still intact. I have checked everything that I took apart from the removal and all is back in its proper place. The car now idles like it is lean or has a lean idle miss. Ran great before I worked on it, might be telling me something?!?!?!?! Any ideas??

At the risk of sounding like a parts counter man; year and model?
Possible sources of backfire if you still have points are timing errors with the distributor and dwell (gap) error in the points. Also valves getting out of adjusment can cause a backfire. Bad plug wires and/or improperly ordered plug wires on the distibutor cap can cause backfires - check your firing order. Also it would be a wise investment to install a "pop-off" valve in the air box if there isn't one. Cheers, Jim

Sorry '83 SC, so no points. It ran great before I took it out so.....? I hear ya about the pop-off valve.

Perhaps a vacuum leak or a vacuum hose that is in the wrong location?