Re: The Duchess Project: 1940 Super 8 Convertible Sedan

Posted by Owen_Dyneto On 2017/7/27 15:27:03

A major underlying cause of burned exhaust valves such as you picture is often the failure of the valve and seat to form a good seal, thus allowing a large volume of very hot exhaust gases to rush at high velocity past the weak point in the sealing perimeter. The split is the result of the erosive action of the gases.

Lots of secondary issues to consider; lean mixtures, steady diet of high speeds, width of valve seat and margin on valve edge, guide wear, stem wear, back pressure, tappet clearances, etc.

I don't understand why folks add all kinds of "stuff" to their gasoline but I doubt that had anything to do with your situation.