Rebuilding a B25SS 1971 motor and the original head needs a stud thread repair so acquired another head off ebay, but on setting up the valve clearances cannot get them to the 8 and 10 thous, one is too tight and other too loose, swopped push rods over and checked followers but to no avail, swopped valves back into original head and put that on and all good again, so what I wonder is this other head I have is from, in the pics the dirty head is the correct original, and the cleaner on is the dodgy one, same part nos 71-2195 but original has PBM 1 and the other PBM 3 and castings are slightly different below the stud holes and one has more fines on tops, any ideas please?
Did you ever solve this?
Is it an illusion or are the valve guides at different angles on the PB3 head?