Hello, I have a 1991 RX7 FC with an N/a motor that I'm currently in the process of rebuilding. I've found a chip about a centimeter and a half big on my front iron between the orange coolant seal and the coolant jacket. I was looking for a exact s5 replacement but haven't found any success on marketplace or ebay. There was is a post about a s4 n/a motor part out and was curious if that would work. If its not possible I'm going to call up a local rotary shop and see if they can supply me with a refurbished housing. Thank you for the help!

 

the front irons are the closest to being interchangeable. also the one i can think of depends on when the S4 iron was actually made. if it was made before 10/1988 then it will have the small O ring land for the front cover
casting can be ID'd by the letter. D is S5 turbo, G is S4 turbo, i'm not sure about the NA's i think its E and F? or C and B?