Originally Posted by
Don Cavey
True, a compression test would be possibly the first step.
My experience:
1970, Germany. 1968 truck assigned to me. I put 4000 miles on that truck in a year, all over Germany, so the truck was not very old then. It was a known issue with valve seals. The motor pool had them for replacement. If I didn't drive the truck at high speed, (heavy load, good and hot), it would foul a plug randomly. All I would do was to put one drop of oil on each port of the exhaust manifold, near the head and start the truck the oil would immediately start to smoke on any plug that was firing. The fouled plug port would stay wet. Pull the plug, flick the carbon whisker out of the gap and off we go!
All of that said, if your engine has that problem, it could be fixed without pulling the head off. The compression test should head you in the correct direction.
Please, let us know!