When rebuilding a 12a what are some of the things i could do to boost the compression using factory rotors? I know lapping of the housings and changing all the seals would do it, is there is anything else?

Also i was talking with this one guy, and he said that when trying to raise the oil pressure inside the engine, instead of changing the oil pump i can just put a used corner seal in the spring that's underneath the front cover. Does anyone know if that makes sense?

 

That would be the front oil pressure regulator. I don't think that would do very much because it normally bypasses at a high PSI level.

 

The guy i talked to said he was using stock oil pump, and by changing the tension of the spring on the oil pressure regulator, he was getting around 110 psi. But now that you say it bypasses it.....it wouldn't make sense that it would work.

Does anyone else has any ideas on that? Maybe there is something else that could be done to raise the pressure?

 

The rear pressure regulator can be adjusted if it's the old style. Add washers or whatever to about 1/8th" or 4mm and it'll be around 85-90PSI. You've just got to find one of those old style regs.

Some people mod the newer style by crushing the top to increase spring tension, or the little pin can be extracted, washers/shims installed, and pin re-inserted also works. I hope some others might post here about the info because I forgot where I read it. Hmm, maybe the Mazspeed forum?

 

You can also buy the older style from RB or Mazdatrix, thats comes set to 80 psi, IIRC.

 

What year block has the old style regs? I've got an '84 engine.

 

A while back somebody told me that not putting the front cover gasket, will help out with oil pressure,but dont know if its true.Im currently rebuilding 12a also.

 

Yes I also heard of not using a frotn cover gasket but just silicone and it gives more room to get it tighter to do something with the regulater..

If any one can post pics please..

I would like toknow a free mod..I dont want to buy a higher pressure regulator.

 

well I did this...I did not use the frt cover gasket but this is only to be able to make sure that the o-ring seals correctly. It doesn't raise the oil pressure. You will have to insert a small pipe in the oil metering passage or silicone will get inside the passage though.

 

I recently rebuilt an "R5" engine that came with a non adjustable type regulator. I replaced it with a '71-'80 adjustable type with a little over 1/8th" thickness of washers. I think it came out to around 4mm. I also did not use a front cover gasket. I just used silicon and double checked the OMP oil passage after I had torqued all the front cover bolts. I also double checked the O ring. The silicon was very thin near the OMP passage and didn't flow in, and the O ring was fine so I reinstalled the front cover and retorqued the bolts.

The OMP works fine and the oil pressure is around 90PSI. This was my very first engine rebuild so I took it slow and careful.

 

90psi is pretty good without having to replace oil pump, i'm probably going to be building just a street port so that much pressure should be enough.

I guess now i should start looking for a '71-80 oil pressure regulator.

 

Yep, that's what you need. The pump was a so-called "high volume" with 17.5mm rotors in it. Very minor wear, so I reused it. This engine was street ported, so I think 90PSI should be perfect.