Jeff20B

I'm rebuilding a 12A soon and need to know a few things.



How thick should the shim be in a rear pressure regulator if trying for 90psi? Is 5mm too thick? I've got two of the adjustable style regulators and the shim in one is a lock washer. A ground corner seal is in the other. The corner seal is thicker than the lock washer by a few mms. I'm curious if anyone here has personally adjusted or has ever purchased an adustable regulator from Racing Beat and/or what shim thickness gives what psi. Is there a chart out there on the net?



I'm also curious about rotor and main (stationary gear) bearing clearancing. How deep does normal clearancing cut into the copper? Also, polishing the eccentric shaft. Is it worth it?



I have a 4 window rear stationary gear. That's right, 4 window (it's actually four round holes). It's used and I'm going to check tolerance/clearance today, but it looks ok so far. It came out of a locked up '74 13B (the front rotor and stat bearings failed and the rotor is still stuck to the eccentric shaft). Again, it looks ok so far.



My 4 window gear has a groove behind the bearing that is visible through the windows. You know, it may actually be this one from RB: http://www.racingbeat.com/resultset...artNumber=10015

Or this one: http://www.racingbeat.com/resultset...artNumber=10012



Maybe all this extra oiling capability is what prevented it from spinning its bearing? Also, the rear rotor bearing lobe on the eccentric shaft looks fine. It seems only the front of the engine was damaged.



Incidentally, I just looked at http://www.mazdatrix.com/b4.htm



Mazdatrix' picture of the rear gear shows the gear teeth to be longer than the front gear. My 4 window gear also has these longer teeth. My 12A's front AND rear gears are BOTH short. Is it ok to use my long geared, 4 windowed stat gear in a 12A? I'm only asking because of this page: http://www.racingbeat.com/resultset...artNumber=10017 where it mentions they are intended for 13B engines only. However, I haven't seen anything that resembles a screw-lock bearing or nitriding... yet.



I'll have tp place a 12A rotor on the end housing before I remove the stat gear, to see if the gear teeth hit the rotor bearing...



Hmm, I may have answered a couple of my own questions already, but let me know if I get these right:



Only the rear stationary gear should have a three window bearing and 'Special-Groove'. The front can remain stock. This means I could probably get away with my 4 window gear if its gear teeth can jive with a 12A rotor.



Clearancing is ok, as long as the oil pressure is high enough to fill the gap. Will 90psi be high enough with normal clearancing and/or this grooved 4 window gear I plan to use?



Thanks for reading, and if you know the answers, please type away!

Jeff20B

I couldn't find the edit option, so here are the links again.



http://www.racingbeat.com/resultset.asp?Pa...artNumber=10015

http://www.racingbeat.com/resultset.asp?Pa...artNumber=10012

http://www.racingbeat.com/resultset.asp?Pa...artNumber=10017



I tried my 12A rotor with the 4 window stationary gear and it's a no-go. The teeth are long enough to overlap the rotor bearing. :rant:



Well, when I rebuild a 13B, I'll have this stat gear available.