Cruise Seems Lean

I’m going to disagree on the engine temperature. At least a bit. 200 is just too hot for this stuff. I don’t know your compression ratio or cam timing or even what plug you are using but that is way too hot for me.

This isn’t an emissions deal so for me, power is everything and that’s too hot. Engine heat will make them detonate. So that lean surge may have been from the engine temp getting up to the point where the fuel was vaporized so much from engine heat it didn’t pull enough heat out of the air stream as it heads for the chamber. That raises the inlet air temperature and you can get a lean surge or even detonation.

Of course, you can get the engine too cool and get into other issues, most of which can be cleaned up with annular boosters. Which if you like to tinker with this stuff changing boosters is relatively easy if you have the tool. It’s about 200 bucks for the boosters and banjos. I’m not saying you need that. But it’s an option if you can get the engine temp down.

Pictures of the plugs and some specs would help.

BTW, in the /6 forum, @RustyRatRod has a thread outlining his tune up with a higher than “normal” compression ratio and how engine temperature affected his tune up and such. Maybe he will see this and add his 20 cents. His thread is worth reading.