Thanks for the response, I value your experience. As posted above I originally thought it was a blown EI so the timing has been removed and reinstalled so my original strobe timing is undone. I did mark the cases so I could return close to the settings but that won't be any guarantee of accuracy. This 64 engine has no access port or notch in the crank for static timing so I purchased a later year primary cover to facilitate use of a strobe and used the stick method to determine TDC. Looks like I'll be buying a dial indicator to get an accurate mark at TDC, especially if 2° is going to be the difference between running or blowing up.Surely the timing has already been checked at 5000 rpm,and it hasn't changed.How accurate is the timing mark if you check it with the timing plug?
If you move the stator plate 1/32" clockwise,it will retard the ignition approx 2.5 degrees.Even if the timing was right to start with,that would cause no harm.
How good is your fuel?What's the Anti-Knock Index?Does it contain ethanol?This will affect how much timing you can use.
If the pistons had more than 0.0045" clearance at the bottom of the skirt,this shouldn't happen.The cylinders will probably clean up with a hone and not be too loose.They usually do,even if a piston melts.
The last "pure" gasoline station in my area now has started selling only ethanol (up to 10%) mixed fuel so I'm out of luck in that arena. Best anti-knock here is 91.
I'll be shipping the cylinders and pistons to a regional shop that does very good work, he'll know if I can escape with a hone job or if it needs an overbore. I'm betting I measured the clearance incorrectly and dinged myself through ignorance.