I have a 350 with problems... Its a 72' short block , low compress. but good compression in every cylinder. Powerpack heads 1.94-1.60 valves redone awhile ago. Holley carb and air-gap intake. Crane cam : Lift: .480''/.480'', Duration: 284°/284°

The top end came off a good running 327, but when I put this engine together... it idles fine, then at low rpm its rough but still somewhat smooth.. at like 3000 rpm it seems to eat itself up. It Revs up then its seems like a major load is placed on the motor. I checked compression strong and even in every cylinder.. tried different carbs, timing is fine inside the block but at 0-6 degrees it runs worst and pops back up the carb.

I think maybe valvesprings are shot? Is the cam just way to big bleeds off all the compression? I ve the motor apart 3 or times its just keeps getting more and more ugly as i run out of ideas... any ideas?