Rebuilding an s4 engine, the front iron is not re-usable, coolant seal groove damage.

I have another complete s4 with super low compression, so if I absolutely have to I can spend this morning tearing that apart.

I also have a dismantled s5 engine ('90) that blew a seal in the rear rotor, motor was actually running on the front.

My question is; Will I suffer for my laziness if I use the s5 front iron instead of the s4, or are the differences enough to worry about?

 

I can't think of anything major as to why you can't.

This thread brings up the oil o-ring casting size change, so be sure you do that correctly on your rebuild.

https://www.rx7club.com/showthread.p...ons+difference

 

these are non turbo irons, correct?

 

Correct, non-turbo.
I did notice a difference when the s5 housing inside to clean it.

There is an exhaust return port? A small slat under the regular intake port.

I should have remembered this, it's also the biggest difference in s4 and s5 lower intake manifolds.

I ended up taking the other s4 front iron off, and it was in immaculate condition (I think that motor actually ran, but didn't have enough compression to hold it on a hill when the car was in reverse)

Anyway, just to finally update.
Major differences are the intake ports, and the casting for the oil o-ring.
Intake port slat can be filled with 5 minute steel or jb stick (I've been told)
The o-ring casting difference can be compensated by using an 89-92 front cover gasket, and the teflon ring with the o-ring.

Thanks guys.