My first rebuild with the "Pop Mechanics cam" many years ago did the same thing. Steady Mobil 1 diet too. ElectraJim
Most off the shelf Mobil 1 has only 800 ppm zink. NASCAR engines have Mobil 1 0W-30 with 1750 ppm zink!! Mobil 1 15W-50 has 1200 ppm zink. I'm thinking of using the 15W-50 because it has barely enough zink (1200 to serve a mild perfprmance vintage street engine (450 HP). CAN 15W-50 BE TOO THICK FOR A 455 BUICK ????