are the front and rear housings interchangeable? i know they come labeled with an "f" and one with an "r" from the factory but they look identical to me. is there any reason i couldn' t use a front rotor housing for the rear?
thanks

 

you can switch up

 

alright thanks

 

same....

 

The only difference is the port air passages by the exhaust port.

 

and some newer only have the knock sensor outlet on the rear

 

Why would that be? All 89+ rotorhousings that I've seen in my life, front OR rear, have the knock sensor thread cast into them. Sounds like you may have seen an engine with a 88- front rotorhousing installed. They make F and R housings from teh same casting, btw, so that wouldnt make a difference. There is a difference in the 88- and 89+ casting, though, plug timing changed.

 

no, ordered them brand new from ray crowe at mazda, F had no knock sensor, R had one

 

I don't see how that would make a difference?

 

That's not right man. All 89+ turbo engines have the knock sensor placed on the F rotorhousing stock. Not that it makes a big difference, but I would probably have raised the question then, because that obviously is not the right rotorhousing for your app.

There is a passage on both sides, under the exhaust port. IF you look at a housing, you'll see that one either the front or backside of the exhaust port (one of the 2 passages) will have an additional hole drilled, leading upward and into the exhaust port itself. This is where airpump air is injected into the exhaust stream to prevent afterburn. F housings have this passage drilled on the FRONT part, rears have it on the rear. There is your difference.

 

so it's only going to matter on a air pump car?

 

Air pump and emissions, yes. As for the actual running of the engine adn compression, it doesnt matter at all. The external and internal surfaces are identical. You can run reversed R/F, 2 R's, 2 F's, it doesnt matter.

 

That's what I figured. I've been swapping them around for years with no ill effect.