Kent, great report with 1st hand experience to back up your comments. I suggested using a release agent (grease or vasaline) on the valve cover and Great Stuff without a release agent on the head. Have you tried this technique?
RonR
1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1964 CJ5
| 
