I've been pre occupied getting the radiator recored on my 85 and installing it today, it was leaking and down for almost a week. I changed it out 8 years ago, I should have had the old one recored then, for a spare, but I never thought I'd have it this long.
I have possible clue on the 86. I notice the #1 piston is very clean compared to the other three, same for the cylinder head. Don't know what to make of it. It seems unlikely that the head is cracked.I thought I might have pinched something on reassembly. The rocker assembly seemed okay on removal. It seems that intrusion of coolant to the combustion chamber must be cleaning the piston and head, right?