My 440 ran Pertronix with a recurve,452 heads and 750 Carter Marine carb,TTi 2.5" system
I find using NGK's or Delco plugs worked great with today's "quality" gas swill.
I gapped them at .43 thou.
Big blocks build up heat high and fast.
Your "spark" means squat when the gas boils or evaporate before the plug has an inkling to light it.
It can cause a lean condition and even more heat.
Blocking the heat cross-over from the intake,insulating between the turkey pan and intake,use a 1/2" spacer between the carb and intake.
Use heat sheathing on the fuel line going to the carb.
Why?
With a laser temp heat reading gun,and at operating temp after warmed up,the thermostat housing will be at 195-210F.
When pointed it at the base of the carb..106F!
A cooler denser charge will provide a better burn and help the plugs do their job more efficiently.
I live in the Great White North and experienced issues like I was living in The Mojave desert!
Ethanol really sucks.
Even some "contains no ethanol" fuels have a much lower octane level compared to when our cars were new.
Hope this helps
