note that the problem w/ unleaded and old vehicles is
recession of the valve seats - hence the seats are replaced w/ hardened ones - doesn't really have anything to do w/ the valves themselves
unless you're drag racing or pulling a heavy load constantly that causes extreme heat [like where the exhaust starts to get red], there's NO problem running unleaded in an engine without hardened seats
here's what Chevron
had to say about it after tetra-ethyl lead was banned
Bill
