Carb

[Gypcmechanic]

It doesn't start to detonate until about 60. And it is really bad. The 100 octane isn't really any different other than the knock. Remember too the most aircraft engines are low compression I was running it more for the lead. I'm going I try the carb. It's the last thing really. I've replaced everything else

 

[sgarver]

I just read your other post about changing the heads. Did you also change the lifters or at least pull them out and compress them? It could be a case where the lifters are stuck in the position they were in with the old heads and with the new heads they are keeping 1 or more valves slightly open. Just a thought.