Phil,

Your description of exhaust valve seat recession is quite convincing. I previously thought that lead was advantageous to valves according to the hypothesis that lead in the gas would plate out on valve and seat contact surfaces and improve heat transfer.

It also makes sense as you suggest that the lead would metallurgically alloy into cast surfaces and provide a hardening effect. Any metallic crystal structure is strengthened by dispersion of dissimilar sized atoms. These break up the shear planes of the crystal structure and entangle the dislocations (discontinuities in the structure that facilitate deformation).

I'll talk to my machinist about valve seat inserts and let you know what he thinks. Sounds like this is the way to go. I don't care to try to develop good seats by running leaded fuel.

If I do the seats, go with the Manley valves, change the cam gear to the steel set, and replace the crank seal felt packings with late model rubber lip seals, then I should end up with a highly reliable, oiltight engine. That would be nice!

Later,
Al