Are you a "top engine builder?"
Depends on what you call a "top engine builder". If you mean do I work for a formula 1 team or JGR in engine development, then no. If you mean have I built engines for professional racing, then yes. I also have 2 degrees in mechanical engineering and am the third generation of professional engine builder.
However, that bears no importance on the subject at hand, as I have not mentioned my own work once. I acknowledge that I am a small time engine builder and thus try to build off of the research and development that others have done. Guys like Larry Widmer, David Vizard, Phil Burkhart, Hendricks racing, Roush Racing, Ron Hamp, Jesse Williams, etc... all have much more experience and much more research and development money than I do. When all of those guys discovered that lapping was useless and quit doing it in the mid 1970's, I think that says something. When all of the manufacturers followed suit in the 1980's, I think that says even more.
You can probably count the number of people on this board with coated valves in their SOHC 4 on one hand. Most of us are using 40 year old parts that are still in serviceable condition.
Again, the fact that a valve is coated or not does not matter. Coated valves were only brought up because of the fact that their development was completely based on the discovery 40 years ago that standard steel valves did not need to be lapped. Today's automobiles still use uncoated steel valves just like the SOHC4 engines, and many of those engines are still based off of the original designs from the 1950's, yet most manufacturers have not lapped these valves in decades.
The fact that cutting equipment exists that can produce a valve sealing surface where lapping is not needed doesn't change the fact that lapping is beneficial to renew 40 year old parts- old methods for old machines.
Beneficial is a subjective term. Lapping can help seal valves that are leaking in some cases, but at what expense? If you are lapping two worn surfaces together then you are not correcting any wear or cupping, you are just making a band-aid. While the valve may seal, it's life has been shortened. To some this may not matter (apparently this community does not care), but to me engine performance and longevity are key.
Everyone jumps down my throat saying that I am wrong, but not a single person has provided any sort of information or research demonstrating that lapping is necessary other than "APE does it so it must be necessary". I think the fact that Honda, Yamaha, Kawasaki, Suzuki, Ford, GM, Chrystler, etc have not lapped a valve in decades and their engines all seem to run just fine shows that lapping is not a necessity.
If I knew that I would become public enemy #1 for suggesting a technique less than 50 years old I never would have chimed in. Just because an engine is old does't mean that the same old techniques that were marginal back then need to be used. The rest of the world has moved on.
