The Effect of Some Fuel and Operating Parameters on Exhaust Valve Seat Wear

We are currently faced with the possibility of operating millions of passenger cars and trucks on gasolines free of lead whereas they were designed to operate with leaded gasoline. The studies discussed in this paper illustrate the potential engine damage in the form of exhaust-valve seat wear that could result from such a move. This work shows that the inclusion of phosphorus in zero-lead gasoline is not a complete solution to the exhaust-valve seat wear problem, but that as little as 0.5 gm of lead per gallon in gasoline can provide complete exhaust-valve seat wear protection under relatively severe conditions of speed and load.

Comparison of photomicrographs of exhaust valves and exhaust valve seats run with zero-lead and 0.5 gm leaded gasolines permits speculation on the mechanism responsible for exhaust valve seat wear in engines fueled with zero-lead gasoline.