The Effect of Low Lead Gasolines and Some Aftermarket Lead Substitutes on Exhaust valve Seat Wear

In 1985 the U.S. Environmental Protection Agency instituted regulations which have ultimately limited the lead content of leaded gasolines to 0.1 grams of lead per gallon. There is currently very little test work on the potential for exhaust valve seat recession while running an engine with a cast iron head without hardened exhaust valve seats on gasoline at this lead level. Therefore, we have examined valve seat recession from low lead fuels.

The test program described here evaluates test conditions and additives which can affect exhaust valve seat recession in mid-1960s vintage heads. Cylinder heads produced after the early 1970s had induction hardened exhaust valve seats and were not susceptible to exhaust valve seat recession. Specifically, tests were run in which lead, air/fuel ratio and engine hardware (valve rotators) were varied and evaluated for contribution to the valve recession process. Tests were conducted on fuels which contained lead at 0, 0.05, 0.1, 0.2 and 0.5 grams per gallon to show the effect of low lead fuels on valve recession. Two proprietary aftermarket additives were also evaluated as potential replacements for lead.