Quote:
Originally Posted by psalt
There is a welding and tearing process that occurs between the seat and the valve head in normal operation.
|
In the way back, lead in the gasoline helped soften this action by getting between the valve and it's seat. One of the big fears of classic car nuts that the unleaded gas would cause premature valve wear.
I think some of the valves (exhaust?) have a pocket in them filled with sodium to deter heat saturation. Makes them a little lighter as well.
Four thousandths of an inch is not that small a number. If you have your reading glasses on you can use a machinist scale and measure distances within two or three thousandths.