Also, one other thing I thought of- did you take all the burrs out of the combustion area of the head? These can lead to preignition and over heat the cylinder.

Oly in Oregon

Rest in Peace

1945 GMC COE Victory Truck
1953 Willys CJ3B
1955 Chevy 1st series 3/4-ton
1958 WIFE Last series

Never say "Whoa" in a mud hole