Well, i've decided to use my contacts and call/email several other builders in the country to get some information about this..
One builder in LA (Louisiana) stated to me that he has not seen any engine he took apart that was failure due to clearancing the rotor. He also stated that its not necessary for street engine thats not high HP or high Rev.
Another builder in NE stated to me, "the only time i have seen failures of that nature (rotor hitting side housing) is from a spun bearing due to lack of oil.
for the builds you describe (less than 400rwhp and 8k rpm) we do not clearance the rotors as you describe."
**Description I gave is the RB quote regarding clearancing rotors**
Next builder I've contact is someone most of us here knows...
He stated this..
Quote:
I take apart a lot of FD and FC engines, probably over 500 since I started in 2001.
These are stock (built in japan when the car was new), mazda remans, and a few outside builds as well.
I do not see any FAILURES as a result of rotor to iron clearance. What I do see is scraping and rubbing on the side tips of the rotor, especially on FD engines for some reason. By this I mean, the material above the corner seal, usually shows signs of rubbing the iron walls. This is from shaft flex at high rpm, which lets the rotor move out of parallel alignment with the iron. Oddly, the FD rotors weigh exactly the same as the 89-91 turbo and 89-91 non turbo rotors, however the FC engines rarely exhibit this problem. I am not sure if this is because FD owners are more abusive in general toward their engines and stay at or near redline more often, or if it is due to the power output of the engine being somewhat higher. I lean toward the former, since 50-100bhp should not be significant enough to cause shaft flex in itself, the consistent use of high rpm would have to do it. Note that the 89-91 non turbo engine actually has a higher redline and rev limiter than the FD, but I still rarely see the symptoms of rubbing on those rotors, while almost EVERY fd engine I take apart has it. I still think that is because FD drivers are more prone to high rpm driving than FC drivers.
This "damage" never adversely affects the rotor, corner seal, or iron. The only time I see genuine damage to either, is when an oiling issue has arisen, such as oil starvation, a spun bearing, etc. that lets the rotor come into much more significant contact with the iron.
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I'm waiting few other builder responses to this topic.