Is there any big diffences between the early engines and the later 12A engines?

 

Yes.







Oh, did you want to know, too?

Looking just at the blocks, the '79-82 had the same rotating assembly (except for the flywheel, which was lighter '81-82) however the rotor housings and side housings were different. The SA engines had the air injection port inlet in the rear rotor housing, while the FB engines had the inlet under the center intake ports. Allegedly the SA engines had more exhaust port timing but I've never checked that out. Piddly-**** differences include the SA engines have no hole or boss for the oil pressure sender (SAs had no pressure gauge or even an idiot light) and you cannot use SA-type spark plugs in the FB engines without a special thin spark plug socket, unless you modify the rotor housings to get rid of the boss.

Forgot to add - the '80 California emissions engine had an EGR valve! Easy to forget that little tidbit...

The '83 engine is the same as '84-85. Lightweight rotors, flywheel takes 225mm clutch.

 

Thanks Peejay, that is just what I needed!

 

What are ya planning?

 

Wow, I thought I knew quite a bit about the 12A. But this shows that I indeed do not. Oh well. You learn something new everyday.

I didn't know the rotors in the 83-85 engines were ligher. I also didn't know about the housings being different. I thought they were all the same, with the exception of a few added on parts.

 

peejay is the man...

 

Yes, Peejay is the man.

Well, I am helping my son put together a 73 Rx3. A freind is giving us an engine from a 1980 Rx7. I just wanted to know a bit more about the older engines. I have just heard about an R5 casting and thought that there was more to know.

Thanks again

 

Correct me if I'm wrong (probably am but...) but the R5 casting was a 13B engine in the cosmo in the late 70's. I believe it was only available in Japan at the time too.

 

The nitrided R5 was JDM. The painted black one was '76 Cosmo and maybe RX-4. REPU always had 3B castings (I think).

R5 rear plates also do not have an oil pressure hole. You can either drill and tap the banjo bolt, or drill and tap the plate itself. I've done both and I bet you can guess which one was more difficult.

 

Don't forget the beehive cooler. On second thought, definitely forget about the beehive.....