It was doing long approaches at idle. Plenty of motors don't like that. Pistons get loose. Inlet valve guide fit has to be good and can be .001" if the finish is good and parallel. The exhaust needs more and could also pass oil on a glide. Yes oil (and air can go back in if the flange leaks.) When power is on, some of the gas goes UP the exhaust guide and contaminates the rocker box. EXCESS oil can lower the Octane and cause detonation. Nev