|
the time off the seat at lower lifts is increased dramatically.
I have had some customers tighten up the lash to .002" to get more top end. I wonder how hot they are getting the cylinder heads and how wide the lash is really getting.
Hello John,
Anyone that does this has already made the decision that the 15,000 service interval is irrelevent and they are willing to accept the damage. They probably also have narrower seats that stock and will be on to their next engine before long. There is an recent, interesting SAE paper on the sequence of events leading to exhaust valve burning. A lot has to do with the surface finish on the valve and the seat. The valve is eroding the seat surface in a welding and tearing pattern, the surface finish breaks down, the heat transfer is impaired, then the seal breaks down and the hot gas burns a trench. You can probably estimate the additional heat by estimating the percentage reduction in seat time.
__________________
Paul
|