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Hello

I am rebuilding a 1990 FC RX-7 13B engine with suspected blown coolant seals. Can anyone confirm if Series 4 (S4) housings are interchangeable with Series 5 (S5) ones for this rebuild?

Also, which coolant seals should I use with S4 housings?

Any advice on ensuring compatibility and performance would be greatly appreciated.

Thanks!
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j9fd3s

iTrader: (3)

first, the coolant seals are the same from the start of the FC in 1985 to the end of the FD, 2002.

two, the center iron for the S4 NA is weird, it has the EGR, and then the ACV uses the end irons, so if you need to pass emissions, its not compatible. the S4 T2 and all the S5's are pretty similar though
the rear iron for the S4 has the full mounting pad for the old top mount starter, with 2 bolts. the S5 only has 1 to make room for the intake manifold.

for the rotor housings you might want to verify that the ACV passages aren't reversed S4 vs S5, if its needed. if they are you can probably just swap them front to rear.

imo its better to build the engine so i could pass emissions if needed. ive seen a few cars where the owner moved here to California, and getting it smogged required an engine rebuild to have the ACV ports functioning

pzr2

iTrader: (4)

Wait, what?

I had no idea there was anything different between S4 and S5 NA irons other than the front cover o-ring boss. I just put together a frankenstein engine out of front and rear S5 NA irons, an S4 NA center iron, and S4 T2 rotor housings. Everything else like the ACV and LIM are S4 NA. You're saying my ACV won't work as a result?

j9fd3s

iTrader: (3)

if you kept the S4 lower it might, blow some air through the big round passage under the ACV, and it should make it to the exhaust ports "Port Air"