Originally Posted by cdelong
mx... seems like we are on the same page
I did not convert your metric units of clearance to what I measure in..... thousandths. I do know that every 0.1mm is .004", so your .55mm (0.022") is a bit lower than I shoot for on my standard set-up of 0.028". My 0.028" standard falls right in the middle of your band at 0.70mm. In FL I may add 0.1mm shim and occasionally I may remove one.
We are very close on .12 engines as well. Again, I fall right in the middle of your band at 0.022"- 0.024" (about 0.6mm) on my starting point.
I agree with all your other tuning points on humidity and temps as well. Usually there is one over-riding factor that makes the determination on how to best tune the engine at a given set of conditions. The determining factor could be different with each new set of variables, but good to see someone who is on the same page.
Yes, my lowest values are what I consider to be the absolute minimum clearance before the piston makes contact with the head. This value may be runnable on some engines and not runnable on others depending on combustion chamber dome volumes. Moreso these values are just a guide on what is a mechanical possibility, before you have angry parts.
BK