I just got my hands on an S4 13B motor. I have an '81 with 12A and am in the middle of a rebuild and 1/2 BP. I was wondering if any of the 13B in internals (corner seals, springs, apex seals) would swap into my 12A and if they would actually be better than the stock 12A internals.

 

Nope.

They won't fit, and they aren't better.

 

Yes and no. Corners seals are 2mm in 13B 12A are 3mm. Side seals can only be used from S3. Springs you need to buy new 1's dont reuse any springs. The oil control rings you can use on any rotary. Dono what elese you might wanna use.
Use 3rd gen corner seal springs and i would use solid corner seals.

 

Some parts will fit, some won't. The way they increased displacement from 1.1 liters to 1.3 is by increasing the width of the rotor. Some something like the apex seals won't fit, they're too long.

 

The only parts that are interchangeable are the oil control seals/springs and the corner seal springs.

 

But since the corner seal springs are the exact same wire-type springs as the regular FB 12a, there's no point in swapping (like there would be from a 13b-rew)

Jon

 

Why not?

 

S4's still used the wire-type corner seal springs. They didn't change until the FD came out and they started using the 'preferred' flat-type springs (found in 13b-rew's). So there would be no point in using the wire-type springs from an S4 engine which are the same type he already has in his 12a.. But I you could still use them if you wanted to.

 

Why would you want to reuse any springs? Buy new springs and buy 3rd gen corner seal springs.