Could it be possible that the head gasket is not correct in some way? Are all MF 135 engines the same? Not familiar with Masseys. I'm basing this on experience with a 1960 Pontiac 389. Later engines had relocated oil passeges to the head. Parts house sold us the wrong gasket set. Got the car out of the shop on Friday and Sunday noticed a loud squeak coming from the heads, My Dad knew immediatly what had happened. Monday morning we had the car cack in his shop and changed out the head gaskets and by 4:30 I drove it home. That's just my 2 cents. If I'm way off base, just give me my 2 cents back and we will never discuss this again.