i recently did some work to my 350 in my 82 trans am, headers, holly 670 electric choke, comp cams thumper cam, and intake. everything went on good, fired it up, set the timing, and proceeded to break the cam in for 20 minutes@2500-3000rpm, she sounded real good and was running great. the next day i went to start it up and fine tune the idle, it was hard to start and when it started it sounds like its missing on a few cylinders and sounds terrible. The plug wire on 7 had been melted slightly by the headers, it was a straight plug which is why it was hard to keep off the header. so i bought a new set of msd plug wires, put them on and the problem persisted.

any advice? thanks

 

Maybe the plug(s) are fouled.
Recheck your rockers.