Gasoline additive

I,ve been told that a lead substitute should be added to the gasoline to keep from burning the valves in these old flathead engines.(48 CJ2A,50 CJ3A) At Auto Zone I find "Lead Substitute" valve seat anti wear additive, made by GUNK. Is this the stuff, or is there something better available, like tetraethyl of lead? Like what used to be in leaded gas?

Edited by russnj - 16 June 2007 at 5:09pm

Later replacement L-134's had stellite exhaust valve inserts, and a lot of older engines got them installed at overhaul. These engines run fine with unleaded. Those with the seats cut into the cast iron block are at risk, IF the engine is subjected to hard use. Some older aircraft engines are in the same boat, when run with unleaded auto fuel (it's legal, in certain cases). One fix for both old engine types: If you can get some 100LL avgas and run a tank through every tenth tank or so, the lead will persist on the valve seat and prevent erosion. Otherwise, an additive is a good idea until overhaul time when you can have inserts installed. This is my opinion, as a old airplane pilot and mechanic who has seen the innards of quite a few engines.