"My dad swears that some of his high-performance Ford engines (Lotus Cortina and others) had valve seat recession when lead was removed from mbgas back in the 1980s. Did leaded fuels aid the valves somehow to prevent valve seat recession, and if so, how?" The popular press conventional wisdom circa 1985, when the lead phaseout began in earnest, was that the lead provided a sacrificial surface on the valve seat to prevent micro-welding of the valve to the seat, which was experienced as valve seat erosion (aka recession). What's now believed to have happened is an economic effect on gasoline blending that impacted engines.
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