Originally Posted by dshealey
As I said earlier, "lapping" should only be done with very fine compound, and only just barely enough to see the seating pattern (2-3 oscillations), never to "fit" the valves. If the pattern does not look even all the way around, then the original grinding was at fault and should be rectified.
In case ya don't know, I have been a mechanic all my life, have built some pretty high performance engines as well as a tech for lincon Mercury toyota and worked indy HD shops,
That is all lapping is for to give the final step for a good seat, you do not want to cut the valve in, which if you have done a good 3 angle valve job shold not be aproblem, but some could lap them to death and cause a wider seating surface, which all that does is create more heat which is NOT a good thing
a good fit valve, the tech would have used blueing to start off IMHO, to check depth/width before and during the seat grinding, it leaves no room for error, well ok one can stil screw up it only takes a moment,
Not that I have ever Screwed up in the thousands or more jobs I have done ! ya know - ( ever, really, ok maybe once) , as long as you catch it your ok as long as you don;t do somethign stupid and damage a seat then have to replace a seat. I never ever had a come back, not on any engine.