I started digging a little deeper into the extra engine, and found a few surprises! It turns out to be a '63 case & cylinders (145 cubic inches), and '64 high- compression heads (9.25:1 compression ratio). The '64 and later engines are 164 cubic inches by means of a longer stroke.
The engine was recently rebuilt. Unfortunately, whoever did the rebuilding should never be allowed to touch a tool! My first clue was the excessive amount of gasket sealer that was used - it was everywhere! Next clue...loose head bolts. Then...no valve stem seals at all! Finally, there was no top ring installed on the #3 piston! My theory is that there was some damage done to the top ring groove - maybe the piston was dropped - and the ring could not be installed. The builder figures it'll be okay with a single compression ring, and puts it together. Well, the top of the piston starts to disintegrate, and ends up destroying itself and the head.
An undamaged combustion chamber for comparison. The dark areas at the bottom of the head is combustion blow-by, caused by the loose head bolts. The cooling air from the fan blows it down.
The lack of stem seals on the intake valves caused the oily carbon deposits. This may have caused detonation, contributing to the destruction of the piston.
Some positive notes...the carbs rebuilt very nicely. They, and the fuel pump, and extremely simple, and rebuild kits are still available - and cheap! I wish I could say the same for the other boxer engines I've been working on!
I can get a new set of pistons and rings - standard or oversize - for $240. A matching replacement head might be a challenge...I don't believe that the damage to the combustion chamber will polish out.
opcorn:
