The muffler thing is completely different. That was read on some srt boards.

But the valve lapping I still fully stand behind my belief that if it's making a good and proper seat then there is no reason to lap it, because my source is very credible and I trust him.

Before putting your feet down on saying they need to be lapped, why not ask them? Or call up some race engine shops and ask them.

give me his name and number i'll call.

Even if we suppose that this one, lone engine builder said he doesn't lap valves, every other engine builder, car enthusiast, automotive engineer, engine manufacturer etc. says you do and has the proof you need to (leak down tests and much more advanced/involved tests than that)...

Now, I'm not saying you need to lap valves to have a running, working engine, but we're not talking about merely getting a car to run.

One of my friends is a former F1 Engineer now working for McLaren in Powertrain Development and Calibration and has a Masters in Race Engine Design...would you like me to get his opinion on this or is the opinion of everyone else that's chimed in going to be enough?

Then you're not standing behind YOUR belief, you're standing behind his (which is fine!). When you're learning, you should absolutely be getting opinions from experienced guys. Just stop pretending you are one of those experienced guys, because when you try and regurgitate what they told you, we start playing broken telephone.

P.S. "I know when and why to lap a valve" is not equal to "LAP ALL VALVES!!"

Anyway... I'll leave this thread in peace.