To the original poster, what type of driver are you? Are you a conservative driver, or do you have redline fever?

Driving a car at or near redline is hard on the valves. The exhaust valves endures a lot of heat since after the cylinder is done with the power stroke, it must push the hot exhaust gas past the exhaust valve. High rpm does not allow the valve sufficient time to transfer the heat to the valve seat.

A lean mixture as I said before does not provide enough gas to cool the cylinder on the intake stroke so the cylinder is burning hotter.

__________________
2006 Infiniti G35
2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD
Lotus Europa 1970 Destroyed by fire
Lotus Europa 1970 S2 Renault Powered
Lotus Type 52 1970 Twincam Webers Powered
PORSCHE 911 Targa 1982 The Garage Queen
Audi Avant donated to Kars for Kids
BMW 525IT Sold
Audi 4000CS Quattro Sold
Jensen Healey Lotus Powered Sold
Opel 1900 Sold
Triumph Spitfire 1971 Sold
Triumph Spitfire 1968 Sold
Plymouth "Cuda" 340 Six pack SOLD