Does anyone know the Height, width, and depth of the Front, intermediate, and end housings of the 12A? I'm getting them resurfaced soon, and the shop needs to know the dimensions beforehand.

 

You mean the irons? Housings hold the rotors. I suggest you do some reading on the treatment Mazda did on the faces of the irons before you have them surfaced. Take too much off and they will wear out quickly. If your irons are too grooved to pass specs, pick up another set instead.

 

The specs are in the factory service manual or can be found in a Haynes or Chilton manual also.

 

Racing beat says .007 max if I remember right but I would double check there catalog or someone will let you know if I am wrong. If they are not stepped just run them. The factory coating is nitriding which is very hard. Most local heating treating shops can do this its nothing to special. The shop that will be grinding or lapping your plates should know where to get this done. I don't think RB re nitrides their plates after lapping. Get a copy of RB catalog it has some good info and if you need some plates I may still have a set laying around. I know they can be hard to find

 

Step wear limit is 0.10 mm or 0.003 in. for the rotor side seal, step wear inside of oil seal track is 0.01 mm/ 0.0004 in. outside of oil seal track is 0.01 mm/0.0039 in, stepped wear by oil seal limit is 0.02 mm/0.0008 in.

Download the 85 FSM from my sig line so you and your machinist know where each of these measurements are taken. Section 1, p31/32.

 

ayt. Thanks guys. I might run to Pineapple racing in the next couple weeks to have them check out the irons. I just don't have the tools.

 

RB does not automatically do re-nitriding. Not sure if they offer it as an option.

Also, after lapping regardless of who does it, you'll have abrasive compound in every possible hole and channel in the plates; unavoidable result of the lapping process. It's essential, and I mean crucial, that you get every last bit of it out of your irons before you use them. Unless you like your hard seals to only last a few thousand miles. Ask me how I know.

The evil stuff is painful hard to get off/out. I'd recommend hot-tanking them, preparatory to a lot of time with brushes and garden hose. If you can get (and afford) ultrasonic cleaning, I'd seriously consider it.

Painful experience here.

 

I know, I planed ahead and removed the oil galley plugs and cleaned all the oil passages. Grinding dust will do the same