273 Commando - Coolant leak - Cometic MLS Head Gasket

In this instance it's basically the surface finish of a machined part. What we see is a metal surface cut or ground to a certain finish. but the act of cutting or grinding tears away material, leaving high and low spots on the surface. The Ra value is a number that represents how smooth the machined surface really is. The smaller the number, the smoother the machined surface is. Normal stock type gaskets seal from 40-100 but too smooth and they can't grip the surafces and can move around. MLS need smoother surfaces because they don't really bite They're made to move a little but if the surface is rough, the fuilds can seap past it. Sometimes it goes away. Sometimes it doesn't.