Sounds like a stuck/tight valve, interferring with the piston. Pull that valve cover! I didn't it swallowed the valve destroyed the piston, went thru the water jacket, etc. Mine was a new rebuild with less than 2 hours on it. I sent the head to the Machine shop they replaced guides, springs, keepers,and only replaced the exhaust valves, I installed a mild cam and I think the higher lift may have put the unworn valve stem into a tight guide, guess which one broke(hint -intake) Now have 350 SB installed. See
http://community.webshots.com/user/zeker6 The reason for the V8 Zeke
