BLUE TII

i noticed that the 13B (an '87) shaft that i snapped the photos of has a slightly different oil passage scheme than the 12A.

the front main has 2 oil passages on the 13B, while the 12A has only 1. does it have something to do with the thermal pellet on the 13B?



I believe the 13B simply has a slightly improved oiling system than the 12A. You see, the oil for the front stat gear and rotor bearing comes off the rear oil pressure regulator just like the rear stat gear and rotor bearing, but it must make three more cross drilled 90 degree angles and travel the length of the engine through the dowel pins to get to the front bearings. This causes much more pressure drop than the rear bearing sees and adding one more hole in the e-shaft at the stat gear bearing was Mazda's quick fix to help get oil to the front rotor bearing.



Racers do the quick fix one better by adding another oil hole in the rear rotor for more oil to the rear rotor bearing (just as Mazda did with the front on the 13B) and then running an additional oil line (loop line) from the rear regulator area directly into the front stat gear bearing (through the plugged cross drilled hole already there).

diabolical1

thanks. what you said makes sense to me now.



well, i'm sort of relieved to hear this because my curiosity did not stop at just wanting to know why Mazda did it. i was also thinking if i was going to risk damaging anything if i drilled through the 12A shaft to make it similar to the 13B. hearing you say this makes me want to actually go ahead and try it now.

diabolical1

2 more things ...



1. i just want to confirm ... you did mean rear "main" bearing, right? since there are already 2 holes for the rear rotor bearing.



2. that additional oil loop line that you referred to, is that the same mod that Lynn descibed in post 15? because i think i read about it somewhere else on this board (i'm tempted to say it was a BDC thread, but don't quote me on that). however, i thought it was going way too far for the plans i have.

BLUE TII

Ooops! Yes, add another hole for the rear STATIONARY gear bearing when doing a loop line to the front stat gear bearing.

j200pruf

I know i am digging up a very old thread, but would there be a "correct" direction on the tail of the tear drop or does it not matter.

Hyper4mance2k

It matters. follow the pic Lynn posted. The tail should be exactly that the tail.

diabolical1

you have to pay attention to the direction of rotation within the respective bearings, mains and rotors, and place the tail accordingly. as stated before, the photos provide a good guide.