engine rev problem

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?

Try another distributor, sounds spark related to me.

Hows your engine vacuum try uncorking your exhaust at the mainifolds or headers

Almost sounds like the timming is off or you have some burnt valves.
Did you check the valves before you put them on this motor?

Kurt

You said compression is strong and even. Could you share the numbers with us?

You don't happen to have the nylon coated timing gears on it do you? They will crack and flex under power and throw your timing off.

how much curve in the distributor is the advance working what spring s do you have on it ?

compression was around 140-150 psi in each cylinder. New iron timing chain, stock rebuilt distributor with curve and is working. I m leaning toward bad valves. It was cold yesterday and there was a tapping in the left rear corner of the valvecover, Bad news.