Hi there, The Corvair vert ('64) runs great but it gives one loud knock (one out of 2 times) when I start the engine (only warm/hot) and when I shut it down it diesels for 2 secs. Any ideas? 110/4 engine, 95 heads, Petronics 1, recently overhauled, 95 gas, no pinging. Arend Huisman