My 77 still runs and starts fine, doesn't seem to have any unusual noises or loss of power but the last week or two been noticing a puff of blue smoke when throttling back and Saturday noticed a minor oil leak that appeared to be coming from the joint between exhaust manifold and cylinder head on #4. I'm thinking it's got to be something in the top end on #4 leaking oil into the cylinder. Don't get a puff off smoke at start-up indicative of oil leaking down valve guides. Any other suggestions short of taking it apart and having a look? I was going to check compression across all 6 holes tonight.