I’m thinking timing,too. Upon cold startup, rpm’s vacillate between 1500- 800rpm. Very awkwardly almost like a moaning, but it doesn’t die.
That’s a quoteWaitaminute.... If "He ran them til they were red hot...."???
Hey, Daryl: What did you/they use for valve springs on those heads? I k ow valve float will shut the door on power at higher RPM ( it not usually that low, though?).