Why advance timing?

Well of course it "quote" should "unquote" but you are sort of shooting yourself in the foot by doing so in the first place, regardless of heat issues

You must understand that NOTHING concerning engine controls the automakers did from about 68 --?? the advent of EFI was "for" the consumer, and "all" was for govt smog regulations.

Retarded timing and too--lean carburetion worsened everything from cold starts to poor warmup, to poor general driveability, hot starts, run on on shutdown, poor mileage AND performance, and on and on and ON. Of course not all of that was called by such retarded timing, but some of it WAS.

Also, unless your engine (which is how old, again?) radiator and all other components are in "like new" condition, one would expect some deterioration in systems.