Hello all. I have some questions for the 12a gurus; I have recently purchased two used 12a housings from a friend. I thought they were ok at first glance especially since the chrome plating was intact and absolutely no chipping. However, when I got them home I found some surface flaws on both of them. I've attached some photos. Housing A has what looks like tool marks extending from the leading spark plug hole to the trailing spark plug hole. It appears that some of the chrome has chipped at the deepest of the divots.

Housing A (spark plug side)

Housing A (exhaust side) has some deep scratches .

Housing A (exhaust side close up)

Housing B (exhaust side)

Housing A & B (exhaust port) It appears as though there is a sleeve missing. The guy told me that the housings have been ported.

Housing B (freeze plug hole) It appears that someone has filled in the freeze plug hole and cavity with plastic steel.
My second question is regarding the thread size on the bolts that secure the clutch slave cylinder to the bell housing. I had purchased a used FB gearbox which I had cleaned internally and re-assembled. I then found out about the buggered holes:

Thank you for your advice.

 

The quick answer is yes. The scratches and missing chrome isn't very bad. I wonder if the spark plug missing chrome is caused by detonation?

The JBWeld is covering the water ports used to circulate through the intake manifold. They are not needed if you don't plan to have the ACV on the factory manifold. I'm guessing these housing were not used with the stock Nikki carb.

As for the trans holes, just tap them. You could also use heli-coils. Make sure to use some thread lock.

 

The JB weld is a bit odd. A proper freeze plug and use of the factory o-ring ensures a good seal when running an aftermarket intake manifold.

I bought a metric drill/tap/helicoil set on Amazon and it has come in very handy. Carefully drill, tap, and helicoil those clutch cylinder holes. I had a similar situation on my trans...

How committed are you to a 12A? A few years ago I had my 12A rebuilt and probably would not do it again. I had good quality housings, the irons lapped and re-nitrided, and it was built with all new oem hard and soft seals with the exception of oil control rings. Not that cheap for sure.

12A is a bit of a dinosaur and for me personally it is hard to justify spending $$$ on something that will get harder and harder to maintain. The next engine will be a 13B.

 

@KansasCityREPU - Ah, thank you. I wasn't sure. I am planning on doing the helicoil repair on both holes but I was not sure what the correct size was for the fastener. I'll have to grind the JB WELD plug flat as I'm using the stock intake. The exhaust ports are missing something (like a sleeve maybe)?

@tommyeflight89 - would you happen to know what thread size you bought for the helicoil repair? I know the 12a is a dinosaur but I need to retain the 12a (stock port) because the car is a race car competing in SCCA Improved Touring A class which has very restrictive rules (SCCA is heavily prejudiced against rotary engines since RX7's spanked the competition in GTU in the 90's); stock engine (no porting whatsoever), and stock Nikki carb (de-smogged) with a stock intake. No port matching, polishing, etc... Thank you.

 

If you have to keep the stock port, those big exhaust ports I see in pic 2 might be an issue.

 

I'd find a set of grenaded rotor housings and get the exhaust sleeves from them. It will flow better.

The only real concerning thing I see is corrosion on the sides. You didn't get good pics of that.
Now I have successfully used badly corroded rotor housings by making my own coolant seals out of cord stock and thoroughly gooping everything with Right Stuff. But they did not have corrosion from the water jacket to the spark plug holes, which is a thing that can happen.

EDIT: If you are running in ITA, none of this matters. Those exhaust ports have been ported. Heavily. Extensively. And kinda badly unless they were for a nitrous fed dixie cup motor.

The bellhousing bolts always strip out. Helicoils are your friend, as are bolts longer than the one Mazda used. They are M8x1.25. Just be sure that the bolts are not too long, one of those locations is very easy to get a long bolt in there that locks into the ring gear on the flywheel. That was a fun day in the garage, ("Argh, I just put a new trans in and now the engine won't rotate!")

 

@KansasCityREPU - Would the exhaust ports create a problem with engine performance or a procedural issue with regards to rules?

@peejay - Thank you for your reply. I've ordered a helicoil repair kit from Amazon. Here are some more photos of the coolant passages. I've just noticed some "monkey business" around one of the exhaust ports (JB weld plugging up the coolant passage around the exhaust port).

To be honest, I'm beginning to get cold feet about these housings. I paid 200 bucks each and I still have the option to return them and get my money back.

 

Return them. You need stock ports, those are worthless to you even before any other consideration.

It's kind of a shame, really. They look like they are in decent condition, except for the hack-ported exhaust ports. If they weren't ported they'd be worth $1000 each easily.

 

For fun, here are some chrome flaked awfulness to review. I was able to get new housings back in 08 when they were still available. I’m just hoping that DSL can eventually can hold up to combustion temperatures. By the way, this thing still ran fine. There’s a YouTube video somewhere of it just idling making the James Bond’s smoke screen. Other than hard hot starts it being ornery after sitting for a while it ran actually quite well.