This is my first rebuilld, and I'm rebuilding my 1988 13B N/A with an Atkins Rotor Kit and Gasket Set. My original engine died because a bolt went through the intake and into the rear housing. It tore up my rear rotor and rotor housing. I recently bought a used engine (I think 86 or 87) that was in OK condition, but he said he thought it needs water seals. I opened that engine and found that the rear rotor and housing were OK, but had a bit of wear (more than I would like to put in my rebuilt engine). The front rotor housing, though, was almost mint. Not much wear at all. I cleaned both housings and examined them and could find no difference at all (no different markings whatsoever). I decided I would use the front. NOW, when I started cleaning my housings, I noticed that they were marked F and R. Is there really a difference between the two?? I called Atkins and they said that they believe that they are marked that way for emissions purposes, and that the engine would work with 2 front housings and rotors. I would like to have a 2nd opinion. Any ideas if it will work??? I wouldn't like to spoil the parts I bought on an engine that won't work.

My engine has a "R" stamped on both front and rear housings. I think it has been rebuilt though. I have also herd that it is for emission purposes, something I'm not to worried about.

how does it help with emissions to have it done that way?

I didn't understand about the emissions, either. If they are the same, then marking them R and F would do nothing for emissions. I can notice nothing else different between them. I am puzzled. Don't want to start assembling this bad boy until I feel confident it will work.

F&R housings are for the EGR port. you can use them anyway you want but you will never pass emissions with two of the same. setzep if your car has two F's your engine has been rebuilt. that is a good thing https://www.nopistons.com/forums/pub...IR#>/smile.png

setzep, I guess since you are using both housings marked R, then I guess I will be able to get by with both fronts. But I still wish I knew the mystery surrounding the markings. As I said in the first post, the engine I bought didn't even have markings, but my original engine had 1 F and 1 R. And it was never rebuilt. https://www.nopistons.com/forums/pub...1047683358.gif

Vosko, so do you know what the difference is between the two?? Everything looks the same to my stupid eyes. I don't understand. Will the EGR Port hook up to the engine when I put two F housings??? I don't know the details about the EGR port, so I will have to look it up in the book, but your advice is greatly appreciated. Also, by not passing emissions, do you mean visual inspection, or the actual test? I am trying to understand how this thing works. Thanks.

Look under the exhaust ports one will have a small hole to the left and the other will have a small hole to the right. I believe this is emissions **** that only cars in the states utilize.

where are those markings exactly?

Igy, under the exhaust ports, my housings have 2 holes, left and right. Today I will take photos of the housings to show you what I mean. I checked both holes on each housing, and none are blocked up. So I don't think that is the difference. Has to be something else. And BigTurbo74, the markings stamped on my 1988 housings are on top of the housings, just below where it says "Mazda Motor Corporation Hiroshima Japan License NSU-Wankel". One has a big L and the other a big R. I will photograph the markings, exhaust ports, and whatever else I can photograph today on my lunch break.