I always thought valve seat was either right or wrong and non destructive bluing was used to check how they seat. I don't understand wearing out a valve to see if it seats ok?
Thanks for the replies. Some go one direction and some go the other. When ever that happens it means there's more discussion needed to settle it or to learn exactly why one way and why the other.
I was curious about what kind of responses I would get from the question.
In general when we check out an engine shop were thinking about having work done and we see valve lapping compound where they do heads, we won't take them any valve work.
I thought if a valve seats right it's right and lapping is not needed. I see using bluing or a sharpie pen on valve and seat to see if it's correct and where they meet on the valve and seat, but you never lap valves in. I thought all lapping valves does is cause them pre mature wear. Is what I wrote why some would not recommend it? I agree it's not needed if the valve seats ok.
I use to be pretty good at doing a stepped valve job. But it's been so long ago I don't remember any angles and don't remember how to run a machine to do it. I taught how to do it and it was a pride thing to be able to have it perfect. Now what they do is horrible. Just throw them in an automated machine and grind the heck out of them. Heck the customer doesn't know any better and only expects a few servicing's, before they can get additional bucks out of them. Same with boring, nobody wants to take the time even if you want to pay for their time, just hog it out and make more later sooner.
and... as usual I'm not saying what I said is correct, it's what I remember which is often flawed. ...