I'm rebuilding an 87 13BT and noticed that on one rotor housing, the letter F was stamped on top, and an R on the other. Obviously for front and rear. After disassembling the engine, both housings appear identical. Are they exactly the same? Were they stamped from the factory, or maybe someone rebuilt this engine before and stamped them? I do need a front housing, and I've seen people on EBay selling them...but they never specify if they have a front or rear for sale, making me wonder if there's any difference. Anyone know?

Thanks

 

eh... juss look for ppl in california that has a housing.

 

I believe they are exactly the same.

 

on my rebuilt engine, I have the rear in the front and the front in the rear.. so I guess it doesn't matter.

 

They are the same!

 

I'm by far no expert on this, but if you check the Mazdatrix website, you'll see that they list the same number for the 13B front/rear rotor housing only on the 1985 GSL/SE.
For the FC the numbers are different for the front/rear rotor housing.

Someone once mentioned emission port difference between rotor housings, as well as egr passages (S4).

Here's another I found-There's a water passage above the exhaust sleeve and lower intake manifold stud that's used for the turbocharger. It's open on the rears and closed off on the fronts.

 

my s4 turbo engine had a diffrent water passage in the rear housing than my n/a s4 rear housing did. either that or it was my imagination