Why do engines need modification to run on Unleaded?
A – Lead that is added during the 4 Star manufacturing process acts as a high temperature lubricant, and stops the hot exhaust valve micro-welding itself to its “soft” cast iron valve seat. The exhaust valve may operate at over 700 degrees C., and 75% of it’s cooling is by transferring heat to its valve seat. The fitting of a hard exhaust valve seat and the use of a suitable exhaust valve stops this micro-welding process.
