I disagree. I measured everything I could and could see no run out. I therefore think it’s flex. Even if there was run out, if there was clearance it should not touch, unless that clearance changes when running.
It would be great if someone could measure that detrimental effect on charging. I’m not saying there is no measurable loss, but I can say there is no practical detectable loss ie zero evidence of any loss in actual use.
Back to the gap and flex, if we think about it this way: if the gap (whatever the size) was not changed by either heat or rpm, then the gap we measured when cold would stay the same when hot and spinning. So even if we only had a 0.001” gap, it would never touch.
Therefore, something to do with heat and rpm reduces the gap on a running engine.
Therefore, it’s reasonable to assume that those factors are relative, ie the higher the rpm, the greater the effect.
The only things that I can think of that change with heat and rpm are expansion (heat) and flex (rotational forces).
So, maybe the gap reduces due to expansion, ie maybe the rotor expands more than the stator (highly likely IMHO) and maybe there is flex (a definite factor IMHO). This could be flex anywhere in the system, ie the rotor may distort, the cases, and the crank nose (that crank nose is long, relatively small diameter, and has a hulking great weight on the end of it). I would also suggest that crank flex inside the cases (which we know happens) is also going to transmit to the crank nose as that flex acts on the main bearing as a fulcrum.
Flex is a funny thing. I was once in the test lab at Mercedes when they had an AMG 6.2 litre V8 on the bed that they were videoing for flex. The slow motion video was AMAZING. These V8 blocks are huge, and heavy, and seemingly solid. But in that video they looked like jelly on a plate ! Which was a good thing apparently, as one guy said to me “if zer ist no flex… zen it vill break” …
