Hello:
I have a friend who aquired a complete 12A and a 13B short block. He doesn't know what year the 13B is. How do you know the difference between the 86-88 and 89-91 13B. The Intake ports look like two
ports on the outside above each other, and two single ports in the middle is the only clues I can give you. Thanks.
Rich Gillen

PS Does a 12A front cover work on a 13B?

Good question. I don't know. The six port engine blocks both look the same to me.
Yes on the 12A front cover.

Paul Lamar

Ian wrote:

the S4 ( 86-88) and S5(89-91 ) have a few easy to spot differences, the
main one is the cold start inj. system and the squared off intake
manifold on the S4, less obvious is the ACV, the ACV pumps exhaust
gasses back into the ACV to activate the 5-6 pots, where as the S5 uses
the air pump to activate the 5-6 ports. S4 injectors are low imp. (
square end plug ) where as S5 is high emp. ( rounded corners on the inj
plugs). S4 is mechanical OMP , S5 is electric.  Those are a few ways
from the outside to tell..  As far as I've heard the 12a cover does not
clear the oil pump on the 13B.. and the mounting system for the 12a was
at the front, i don't believe the 13B makes allowances for this.

ian
BAS-- 

I have seen a few 13B engines with 12A front covers. Here is a 3rd gen engine
with a 12A front cover. Perhaps this front cover came from a  13B powered first 
gen RX7 with the front motor mount. Or perhaps the builder
of this engine modified the 12A front cover.

Paul Lamar 

 
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