I will be building my 89 TII engine soon and was wondering about the apex seal groove clearance. On one rotor, its pretty good, its suppose to be .002-.004 with .006 being max. I have .003 everywhere except where the edge of one groove where it is .006. So the clearance is not even. I this okay to use. This is with the 2mm seal.

Ok to try and help you I need a little more info. Your telling us that you have .006 by the apex seal rotor groove close to the corner seal? but .003 every where else?

If that's true, I don't understand why. Why he'd have a larger gap at the edge is weird; usually it's the other way around from people mishandling and dinging the edges of the apex seal groove up... https://www.nopistons.com/forums/pub...1047683561.gif



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Yes Judge Ito, thats exactly what i have. I actually have a couple of rotors that have more clearance by the edge of the corner seal. What happens is the little triangle piece on the stock 2mm 3 piece apex seal, broke off and when that happened, i guess it expanded the groove. I'm not sure this would work but i read of someone useing a hammer to close up the clearance. Another question that i had was, what if the clearance was even all the way through the groove, what would be the max useable clearance for the groove. Or is that limit same as the mazda limit of .006.

Using .006 all across the rotor tip is a bit to much and it effects compression. To much compression leaks between the .006 groove and the engine gets sloppy to kick over. I usually run .002 to .0025 I wouldn't hit back to size with a hammer like somebody told you.

Just what i thought, these rotors are pretty much useless. I guess i'll be going 3mm on my next engine.

But what if i only have a clearance of .006 on one corner of the groove on the rotor, but everywehre is fine. Would you use that?

Something so critical like an engine build I would not use it.

Yeah, you are right.

Just been thru it myself with a 12A rebuild (carbon apex seals).

.006 on one groove == Apex seal broke in 500 miles. Never had even compression on that rotor.