My '54 head is shaved about .030". I was running R45s, but the insulator was bone white. I went from 51 to 55 primary jets, and used different heat ranges and plug types. The plug color didn't change. Always whiter than a sheet of typing paper. My exhaust pipes were black though. Its hard to tell if I was lean or rich, or if the plugs were too hot or OK.

When I pulled the head for the rebuild, the exhaust valves were between black and chocolate. Piston crowns were sooty/flaky, but not pitted or anything. Engine had 10 K miles on it when thrust bearing pounded out.

Would the plugs for an early-model 250 with HEI work in a 235 head? I ask because it would be nice to get the same heatrange with a stock gap of .045".

Thanks
chip

Preaching the Hot Rod Gospel according to the 4-stroke apostles:

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