I can't believe it is a valve spring if your compression is good check for a vacume leak at the intake where it meets the head posibly causing a lean misfire. Is it a dead skip?

BN thanks!
Blue Thunder, I haven't checked vac leaks because the plug is black, not lean.
Cartman, yup its a dead skip. Weak springs can give normal compression when cranking, then float the valves when running.
I swapped the springs but I can't fire it up because I creased the exhaust gasket and have to get another today.:mad:

GO4Broke,

Vacuum testing is not necessarily to look for vacuum leaks, it is to diagnose engine conditions. Particularly good for sticky valves and other top end problems. Look into it.

BT :cool:

Double or triple check the plug wires/ firing order it sounds like ignition.

I will triple check all the ignition because I too lean that way. Blue thunder, thanks for the reminder about vacume testing, your right thats a powerful tool, I just don't use it often. I'll be finishing reassembly tonight and inspect the ignition, then tomorrow I'll fire it up and see what happens. I'll keep you posted...

I rechdecked all the ignition, still NPF. The motor is together and I will run it tomorrow and see what happens.

Well I ran it and the damn thing finally gave me a hint as to the problem. It blew black smoke. I think the port float is sinking and flooding out #2 and #3 which are the front 2 cylinders fed by the upper plenum. I knew it would be something stupidly simple!! I'll be pulling the carb after work tomorrow. This would have been much easier if it had smoked for me before!!