Even if that head machining left little or no material between it and the pushrod location, doesn't the cylinder seal against the head, thus making that possible or real gap in the head material immaterial to the leakage problem?
Looking at the picture of the head again, there is discoloration at the top portion which indicates leakage around the top of the cylinder/head juncture. That in turn leaked into the stud passage. Therefore, were tie rods loose, or was there a bad seal situation in that one cylinder? Also, memory returned briefly: the described aluminum pushrod with the steel caps was on a Pratt and Whitney R- 1830. Others seen before were used in Chev V-8s with aftermarket cams, etc. None of those failed prematurely. George --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
