Two 12A rotors with tight seal slots.

 

Wow!!! Not something you see every day!

 

Where does one find the tolerances and specs for the 12a's? I've looked all over foxed.ca but can't find specs on apex seal clearance, side seal clearance, etc. and so on... Just wondering if it's a specific manual or book or something?

 

What plans do you have for them?

 

This source isn't the end all be all (believe it's targeted at earlier year engines, not certain as I haven't read it recently) but this is one of a few that I've run accross: https://www.mazdabg.com/ftp-uploads/...ria%201979.pdf

There was another one that was a full webpage devoted solely to the rebuild process and was very well laid out, but I can't find the darn thing. It's somewhere in my massive list of RX-7 bookmarks. Somewhere...

 

I have a nice Southern '81 with historical provenance that I want to return to stock, engine-wise. (I threw an FC engine in it to make it mobile, after a couple years of failing to get good 12A parts) It will be a sunny day driver and occasional rallycrosser, only for national level events as well as Detroit region events. Without the ability or desire to run a 3 link rear suspension, I want to keep stress on the chassis tub and rear axle housing to a minimum.

Wait until you see some of the other unicorn parts I have for this thing.

 

Thats the one I'm familiar with. Published in 78 I believe for the 12A.

 

RAD Potential Youtube channels has episode on rotary specs, believe it has the link.

 

That's great, for people who don't know how to read I guess.

 

 

The f'ed up part is, I bought over a half a dozen 12A engines, including one that was "rebuilt" (very, very poorly) in 2008 or so and never run... and these are the rotor housings that were in the blown engine that came with the car. I had them up for sale for a while but there were no takers, and when I found someone with a stash of 12A rotors last summer, I knew what I had to do and bought two pairs from him with good slots. The original side housings have been resurfaced/re-Nitrided by Chip's, and I had him do my bridge ported housings at the same time so I can have the fun engine back in the '84.

If it wasn't for finding these rotors, I was seriously contemplating swapping in a B6 engine from a JDM NB. You can find those drivetrains very easily on eBay for not much money, I guess nobody in the US wants a 1.6 for their Miata... Either way, putting Lumpy McAngryson in the '84 is entirely contingent on making the '81 a pleasant car to live with, since my knees aren't too tolerant of driving a bridge port in the city anymore.

 

the NB 1.6 has smaller valves, lower compression and round cams, its rated at like 98hp. and then all the electronics were upgraded, but the Miata is different from the Rx7, with the Rx7 we have the SAE papers, Service Training books, and the shop manuals. the Miata guys have nothing, they thought the mitchell manual was the factory one

so i guess point 2, is that nobody knows how to hook up the JDM electronics

of course the block, crank, rods and head are all the same, so its a good start for a build

 

I have plenty of Miata friends with 1.6 engines lying around for their cams, and I'd do a Megasquirt anyway, because it is hard to have a B6 or BP and NOT turbocharge it at some point.

One of said friends has a Mazdaspeed engined '90 that I've driven a few times, including as a daily driver for a month or so. It's very nice.



(you can sort of see the snow on top of my RX-3 in the first new seconds of that second video.... off in the back, between the panda Montero and "Oktavia von Seckendorff" my ex-Volvo S40)

 

Almost ready...

 

Lookin good PJ!

 

Almost time to drop it in!

 

Would have been in yesterday, but the hose I bought to repair the MOP lines was the wrong size, and I really don't feel like dealing with them in-chassis.

Got a box full of a disassembled Nikki in the mail today. I bought it for all the solenoids and linkage and choke pulloff stuff that disappeared in the past 40 years. Sadly it's all faded, not nice bright plating like everything else on my carb, but what can you do. People love to rip this stuff off and throw it away, then complain that their car runs poorly... anyway it was literally the only Nikki on eBay that still had everything on it.

 

And so...



My goal is 150hp with the factory manifold. I have a strong dislike of headers on what is supposed to be a pleasant car.

 

That rotary engine gives you quiet power!

 

weird, that thing has the factory installed AC, it is unusual. like a horse with one horn

 

You sure about that? There is a switch in one of the lines on the passenger side, and the wires going to it are just sort of draped over the engine, not part of any harness.

It does have the compressor for factory air, according to Rock Auto's catalog, but the catalog has been wrong before.

What are the defining traits?

 

I've only seen one AC on a 12A car and I had to kill it because,.. it seemed so wrong and foreign in that environment.

 

I kept the A/C in my '80 when I did the street port engine.
I should have kept the A/C in my '85, but I was poor and it went porous.
Some dilhole removed the A/C from my '84.
The main reason I picked up the '81 was because it has A/C.
The conversation went something like this:
"You need this car."
"Well, I gotta think about it."
(three months later)
"You still have that car?"
"Yeah, you want it yet?"
"Does it still have A/C?"
"I'm in Alabama. Of course it still has A/C."
"I'll be down after Christmas to collect it"

 

Nippon Denso compressor, and the lines are all different. There is/was a tax on imported cars with AC, so most Mazda's have A/C installed at the port, but not all. the common one is the GSL-SE and 12A cars with power steering, those all have the factory AC. Most of the rest have the Sanden system, but you do occasionally see one that is factory installed, like yours

 

Huh.
My '85 had power steering, so it was factory A/C.

I don't remember now what my '80's compressor even looked like, but I do remember that the belt tension was adjusted with an idler pulley while this one's tension is adjusted by rotating the compressor. (The cars were built a few months apart - the '80 was built in May '80, this one is, IIRC, September '80)

All it needs now is plugs installed and it should fire today. Need to find/make an air pump to air cleaner hose, and do something about permanently capping off the unused ports.