another 12a teardown thread
 

so I went after a craigslist engine and trans, missing a dizzy and water pump/housing, but otherwise mostly complete. should be a 1980 model from what I have gathered from exhaust manifold and intake traits. no shutter valve and less solenoids than my 83 on the rats nest, but a more complicated carb setup with different solenoids and a power valve? in the rear carb bowl.

cleaned it up, tore it down, giddy as a schoolgirl to tear it apart and see what makes it tick. all of the seals were stuck in their places from carbon. cleaned and cleaned and removed most, killed a couple side seals (dammit!) but everything came out. apex seals look great and are black/grey with chrome tips still smooth and not pitted, corner seals are all metal and no rubber caps, but are smooth at the ends , not looking like atkins from the pics they have online. everything else looks stock to me, but i'm just a noob at this. irons look decent, no corrosion or pitting. housings look bad in a few spots at the edges, like the small end of an apex seal came out. bearings on the rotors are shot- as if it wobbled from high rpm afterwards. red seals came out in pieces, black ones are still rubber band pliable. seems to me like it was a rebuild that never fired or needed more parts. hope to port the irons for my current 12a or rebuild this entirely and be drop-in ready.

Best of Luck. Rebuilt one of my 80 blocks. The Mazdatrix 13b rebuild DVD worth its weight in gold for tips and trix.

Stu Aull
80GS
Alaska

The reason your rotor bearings look like they've seen better days is due to the 1980 small oil pump providing low volume for so many years. Get yourself a so called high volume pump from any 83-85 12A or 13B and you can reuse your rotor bearings.

As for the rst of it like step wear and chrome wear, I'd say reuse everything. Get some Atkins apex seals and a coupel of side seals and call it a rebuild. I say this because you won't find any better housings these days, and if you resurface the irons, I'll have to reach out and touch someone (tonight, you).

resurface the irons??! impossibru! they actually look great. no pitting at the seals/jackets, and I only cleaned with a razor blade and purple power. might hit the seal locations with a black roloc wheel to clean it up but I know I don't wanna hurt the parent metal. I bet this engine sat forever after a rebuild with carbon and wouldn't let the springed parts move in and out to make a good seal & compression. I'm gonna do the $300 atkins kit and add a couple used side seals, port the hell out of it, add a spare edel carb on to the manifold with an adapter/spacer and source some other parts and try to make some noise with it.

This is what I do when I rebuild...

-79-85 12A Rx7 Engine Gasket Kit (N201-89-100) ($118.75)
-69-11 Rotary Front & Rear Main Seal (ARE81) ($16)
-12A 3mm Rx7 Apex Seal Spring Set (1011-11-304) ($56.52)
-74-85 12A 3mm Atkins Apex Seal Set (ARE12-3) ($199.00)
-69-11 Atkins' Rotary Viton Oil Ring Inserts (ARE15) ($39.95)

Grand total $429.22. $445 shipped from Atkins every time. I'm sure if you dont need main seals, springs, and apex seals you can get away at $200, but my out look on it is "while your in there might as well replace xxx...".

Just source out a few used side seals and use those. The housings are iffy, but usable since "good" ones are an arm and a leg. Your irons look good, just be sure to degrease scrape the seal surfaces thoroughly, but dont deform them from too much scraping. Especially on the housing coolant seal grooves. Dont scimp out on your end play either!

the rear housing is the worse of the two. the chrome looks great aside from the gouges in the far edges as they meet the irons. it'll be worth the experience and money to build this one to have as a spare and test monkey. maybe do one-piece apex seals just for good measure?

Do 2 piece.

One piece should be avoided (seems like a dumb show from what little I've seen of it). Get 2 piece because they seal 100 times better at low RPM, especially on used housings, and are easier to start. I'm sure you're interested in an engine that can be started by a starter motor running at 12V, right? Not 24? Which is also a TV show, but better to watch.

Just like the TV show a one piece engine will take 24 hours to start.

thanks for chiming in guys. the bearing copper is a strip from end to end, apparently nothing to worry about. smooth otherwise. rotors are pristine shape and just needed carbon cleaning to get all the seals out of it, as they were wedged down tight and the springs had no chance of pushing them outward and sealing up. gonna need some side seals, broke two at removal. probably install all new springs as well.

something odd, probably a race part or higher performance, my corner seals are recess-less chrome but still utilized the stock wire springs. gonna add the nice thicker springs to these. apex seals are a dark grey with a shiny smooth chrome lip surface. stock or?? if my 12a in the car has given up a rotor ( front wont play nice at all, seems to fire smooth for about 30 seconds then sounds like I'm on the back rotor only and runs like shit) this engine will probably get a few new parts, the $445 parts order and a couple spare side seals, bridgeported, and thrown back in as the #1 engine till the other one is rebuilt. happy I found this for a good price and went after it.

upon further review - stock 3mm corner seals, someone forgot to install the plugs!

You dont need the plugs. Might help it idle way down low, but thats it. They fall out and get ingested by the engine anyway. Ive torn apart several stock Mazda engines that were missing them. So I figure whats the point.

I kept thinking to myself.... they are rubber.. how the hell are they gonna live in a hot ass rotary engine housing for very long...