help with 12a TCP housings...
 

Ok...this is my problem...I buy today a pair of 12a housings in mint condition..with TCP stampled on the top. So the problem is when aligned with my 1984 rotor side plates 2 of the long screws won fit in 2 holes of the plate because the pattern of holes in the housing is diferent..some guys said to me that its reusable the only thing is to fill with epoxy the remaining holes in the rear side plate becuase then going to leaking water...any sugestion? Its posible or not?....and can use 3mm apex seals on this tcp housings?

I don't recommend these housing unless you're using them with early side plates. Not to say it can't be done cause you can but you will also leak oil from where the outer tension bolt is located because the housing will leave a gap . You can use 3mm seal but carbon seals are recommended as iron and steel seal may be to harsh on the early surface . I suggest trying to source another set of housings .

Align a later iron on your housing and drill out the two offending tension bolt holes. A drillpress or mill is good for this. Use dowel pins to align them.

I don't know about the oil leakage heynoman mentioned so I can't comment on it.

Agreed about using carbon seals on early chrome. However they're your housings. Use whatever seals you want. Just know the chrome may not last 100k miles. Is that a problem for you?

Yeah using the early housings leaves a small gap between the rotor housings and the center housing I ran into this problem a while back on one of my engine ended up having to seal it with rtv other then that worked great but if I remember correctly I believe it was 3 tension bolts that didn't line up and I had to machine the rear side housing for one

Thanks Im not worry so much about the tension bolts but I going to use OEM 3mm apex seal....IM NOT SURE IF IS A BAD IDEA SEEMS THE HOUSINGS IS CHROME PLATED..

It's not a bad idea just not a good one it's like jeff20b said don't expect it to last 100,000 mile
Honestly I would say don't expect it to last 50,000
The process that mazda used was never intended to be used with the iron seals and will cause excessive wear .

Ok..thanks....maybe go with atkins 3mm apex seals?

I would use the oem if I had to choose between oem and Atkins .

Agreed about using OEM on these old chrome housings. Atkins are a slightly more abrasive material.

Thanks for posting the pic of the little gap where oil leaks through.

Before you ruin a set of pre 1974 housings stop and try to trade for later housings. Early housings are only meant to run 6mm CARBON SEALS, all the seals made from 1974 onward are an alloy of steel and carbon which is way harder than the seals those housings were meant for. Running modern seals with those housings will lead to chatter marks. and premature failure. you're better off finding RX7 housings, or finding Twin distributor Irons and rotors and running 6MM seals. Twin Dizzy Eccentric shafts and later Eccentric shafts are different as well.

I have a few of these housing and irons from early 12A with 6mm seals. When the old housings are compared to newer style RX-7 12A irons, I don't see any way they will work.

The best thing to do would be to get newer style housings, or get early style irons, rotors, e-shaft like suggested. You would also need to twin distributor from cover. After doing all this, it's probably better just to get the correct housings.