check out these 12A housings I found
 

I found these yesterday I have never seen exh ports like this anyone shed some light on it

http://www.teamfc3s.org/forum/showth...threadid=45087

if the housing in the first pic was listed as a 12a, it might be wrong. seems like i've seen pics of some 10a housings that had exhaust ports like that.

they look sweet how much are they? I assume located in japan.

RX3 10a housings.

they are twin distributor housings all 10a and 12a twin dizzy engines had those

I dont think that all the twin dist motors had those. I had one with the 2 distributor setup and it had a more conventional exhaust port on it. I agree though that was probably a 10 a or a very early 12a for an Rx2. It may have never come to the us. I think that all the us cars had the single exhaust port

no they are definately twin dizzy, your engine must have been rebuilt at some stage with later housings, they were done like this because all early engines had 6mm carbon seals which meant they had a seal leaning angle of 6 rather than the tradional 7 and could easily chip if running over the large port type housings

wow thanks for clearing that up. They where on a yahoo japan auction. they ended for around $150 usd.

Mazda made both 10a and 12a twin dizzy housings with the 3-hole or a single oval exhaust port. Your idea about the chipping apex seals is not right - the three holes was an attempt by Mazda to keep the noise down.

The ones in the pic (at the top) are RX3 10a, as mentioned earlier

Did they sell at that price? If they relist can you PM the link. Thanks

yeah the auction is over I got home late and didnt get to bid on them.

here is the http://page13.auctions.yahoo.co.jp/jp/auction/r16059916

there is some new in the box 12a rotors right now

http://page5.auctions.yahoo.co.jp/jp/auction/e49632067

dont know if anyone needs it but brand new in the box cosmo sports 10A / 10B front iron
http://page5.auctions.yahoo.co.jp/jp/auction/e49898551

http://page10.auctions.yahoo.co.jp/jp/auction/m20151076

that is possibly correct however i have some tech info books from the early rotary research division that claim the exhaust ports were like that to prevent chipping, as the seal starts to float at its natural frequency when the larger exhaust ports where uncovered. it also helped prevent chatter marks when combined with cross hollow apex seals, it seams unlikely they were to reduce noise as they were branded as whisper quiet when sold,you may be correct but info i have states otherwise so i was just stating what little i knew on the subject,but thanks for offering your understanding it just goes to show how much misinformation there is out there

i also see in your profile you are collecting 10a engine parts i have some brand new 10a rotor bearings if interested and some used but good apex seals and corner seals

I have some books (which say something different), and I also have the housings.

R100 10a housings have a single oval exhaust port
RX3 10a housings have the 3-holes
RX2/RX4 12a twin dizzy to NZ and Aussie have the 3-holes
RX3 / RX2 / RX4 12a twin dizzy (US model) have oval ports.

Here are 3 different type of 10a housings:

http://img221.imageshack.us/img221/6455/10a18tw.th.jpg

I have been running this type of exhaust port in my 10a for a while, and have not lost an apex seal yet...

http://img364.imageshack.us/img364/356/ports7ur.th.jpg

Those are not my auctions. I found them when I search for Cosmo and RX-7 parts. I might take you up on the 10a parts as im working getting a Cosmo Sports. I have a family friend whos dad bought one in 67 and parked it in 76. needs alot of love. He would not sell it before becuase it was his very 1st car. now he is older and knows im a rotary freak. He has been hinting that is taking up space.

Cheers mate, I have plenty. Where in NZ are you?

wow I just check there is 2 Cosmo Sports on yahoo right now

http://list1.auctions.yahoo.co.jp/jp...ale=0jp&mode=2
around $18k

there was one last week that sold for $28k

how about 12A current price is $70 with 2 hours left
http://page10.auctions.yahoo.co.jp/jp/auction/m20361946

the middle housings are mfr 10a housings which explains there different exhaust port but it appears you are correct the front one clearely shows an oval port thanks for posting that