Problems after Msd install

[myfirstii]

My friend has a 1972 Mach 1.He has recently had the engine, transmission (c6?) and rearend rebuilt. The engine 351 cleivland that had been bored out to 383. It has a Msd 6al ignition with the MSD distributer,coil,and wires. It has a holley 650 carb. The car ran fine up until we put the Msd ignition, coil, distributer and wires on.After we installed them The car would die at stop lights at anything 2000 rpm. We reinstalled the original ignition system to see if the Msd was bad, but it stil had the same problems. After reinstalling the msd we ordered a new carb and that fixed the dieing at low Rpm but now whenever the car is warm and we've been driving it for awhile the revs tend to jump around at a constant speed and the car backfires. Also when he would take his foot off the gas the revs would continue to jump around and the car would sputter. Is this a transmission problem or what?? Im beginning to be clueless.Any help would be great.
Thanks,
Pat

 

[GaPonyFarm]

Plug wires might be on wrong, or you may have a bad connection if you used the universal wire kit, and cut them yourself.

Could also be a timing issue... set it a 32 degrees and adjust from there.

 

[2nd Mustang]

Vacuum leak? Spray some carb cleaner or WD40 around the base of the carb and intake manifold, check for change in rpms or smoke like in my case when I sprayed carb cleaner on the intake gasket area.

 

[paintballtommy]

..

 

[paintballtommy]

sounds like a vacum problem. does it rev in neutral fine? or does it only have these symptoms under load. if it happens under load it could be an ignition problem.

 

[jesserose17]

I agree with GaPonyFarm - could be either bad connection with MSD ignition system or timing issue.