12a from a 1985

Engine was sitting for a while. (Not sure how long)
finally got to tearing the engine fully apart...
apex seals / side seals all are perfectly fine on visual inspection.(will be replacing everything besides apex seals on rebuild)

My assumption was car sat because coolant seals failed.... engine sat with that crud in it.
Bottom chrime looks like it was eaten away in a way... (I also could have chipped it myself trying to turn the engine.. &#129760

picture is after i cleaned the housing with degreaser and a soft green pad. Currently oiled up while I decide what to do...

No scoring on the chrome besides the area that flaked off.

Rotors look fine as well. Some minor surface rust and a bit of carbon buildup. But that all mostly came off with a scrub and ultrasonic bath)

Is this housing usable? Repairable?
or just go find another housing.


Thanks,
Entropitus

 

That housing is junk. You'll have to find a replacement.

 

Is this even a serious question? That housing closest to the camera looks like Godzilla chewed on it! That would never build compression and even if it did, it would ruin your Apex Seals within a few hundred miles. Post a WTB in the For Sale forum and look for options close to you. Good luck,

 

i figured as much. Just posting to see what options i had as a last min effort and seeing what people say.
First time working on rotaries so wanted to be sure.

Thanks for the replies.

 

It is possible to modify 13B GSL-SE rotor housings to match the dimensions of your 12A housings. This is a common practice because 12A rotor housings are no longer produced by Mazda. 13B GSL-SE housings are still available and "relatively" affordable, however the machining process is kind of pricey. You might be farther ahead to source a good used 13B. This will help to future proof your car's engine to a certain extent.

 

Are you talking about grinding off 1/2 cm from each side of each housing? That's not an easy task, and you'd also have to cut new water seal channels. Maybe I'm missing something, but nobody would be doing that on a new $750 (×2) set of 13b SE rotor housings when you could just build a 13b, and if you were going to upgrade to a 13b, why not pull an engine from a 2nd Gen car? I'm not following you, but good luck to OP on getting his car back on the road.

 

at this point thats one of the options that i was leaning towards... Cant find any good condition 12a's... or if they are good condition around 600-700 which at that point im better of doing a set of 13b SE's
And doing a 13b with my 12a irons. (but would have to get new rotors / eshaft / rings / seals)

Could just go full 13b too if i find a good deal on a used engine + housings. (then factor in new o's and "maybe" seals)

last option is use atkins 12a grinded... but thats 1300 for one...
I guess would "save me" more off the bat because I have everything else already ready to go.

just spending last couple days searching the market..


Could go the cheap route... buy an "ok" 12a housing for cheap. get the car running with startable compression and whatnot... untill i source a 13b and or 13b parts... haha... just to get it working again.

 

600-700 is a steal, I've seen good 12A rotor housings at 1500 each.

 

"just switch to a 13B" becomes a little tricky when it comes to everything else attached to the engine. Nikki manifolds for 13Bs aren't the easiest to find so a Holley or Weber would have to be used along with the associated learning curve.
Exhaust is more easily solved with money or tools, but trying to keep a stockish system requires a custom pipe to mate an FC manifold to the rest of the system.

 

I found that 12A and 13B exhaust manifolds are identical except for the bolt holes. The ports are 5mm offset on 12As and 5mm offset the other way on 13Bs. The pads that the mounting holes are in can accommodate the difference.

When . I had a 13B in my '81, I just took a 12A exhaust manifold and ovaled the holes, and bolted it up. I had a DHLA "in stock" that I bolted up to the engine. Then I found that the FC engine had at least one cracked coolant seal land and it drinks water.
oddly enough I had good 12A rotor housings from my dead engine, but it was good side housings and good rotors that I had issues with. I took my original 81 side housings to Chips to be rebuilt and I found a stash of 12A rotors in excellent condition from a local racer who sold them to me fairly cheap (iirc $400 each for a big box of them). So I got to have a stock 12A again.