I thought that lead was supposed to protect pre-1980 valve seats.
That was pretty much a myth like "Keep a hot engine running while pouring water into the radiator". I call those tidbits of advice "Old mechanics' tales", sort of like old wives' tales. Lots of hard valve seats have been installed unnecessarily because of that advice. Stellite exhaust valve seats are only really needed when running very "dry" fuels like LPG or liquefied natural gas in engines that see a lot of full throttle heavy load situations. The way most stovebolts get pampered, hard seats and/or lead additives are an utter waste of money. A 5% mix of Diesel fuel (1 gallon of Diesel to 19 gallons of gas) provides a little valve guide lubrication, and it's a whole bunch cheaper than any sort of gas tank mouse milk gullible people add. It also raises the octane rating of unleaded gas about 5 points by increasing the specific gravity and slowing down the burn rate a little. Before an idiot assistant principal trashed all my dyno run files, I had lots of documentation on the diesel trick.
Jerry
