1) Pull manifold AGAIN and install special gasket that blocks exhaust port at the upstream end. This should lower my carb temp a bit further, and it makes sense to mediate the heat issue as much as is practical as a first step.(note: the carb body was approx 170 prior to spacer , now is approx 150 , better but still above the 135 bubble threshold)
Unless this engine will be in a trailered racecar, I would suggest at least reconsidering that option.
I started working on automobiles in 1959 (my own, Dad's before that). In that time I have made many mistakes, and will probably make a few more.
But blocking the heat cross-over on my 350 was one of the top three DUMBEST mistakes I have EVER made on things mechanical!
Consider the Law of Unintended Consequences and how it might relate to idle quality. (Or, maybe your heel/toe technique is better than mine) ! 50 years ago, it was pretty good, now the knees don't work as well LOL
Jon
