War Eagle1 A 3.88$ quart of marvel mystery oil would be a cheap test to answer a question. In the old days they would grind the valve seats with just a 45 degree stone and leave them wide. Didn't know any better,that will contribute to a cough. When they lapped em they had no way to narrow the seat either.Would give it a pint to a tankful and see,also check other stuff mentioned.
