ok, will the the block(just the housings and rotors and such) from a 86-88 fit into a 89-91 rx7, using all the components(intake/exaust, and so on) from the 89-91 onto the 86-88 block? without changing ecu's and motor mounts and such, if so will it be worse than the 89-91 block?

 

well the block will fit but i know that the s4 houseing spark plug holes are differnt than s5. dont think this will matter but just food for thought

 

u gotta change the front cover or do something with the oil metering pump

 

are you swapping an S4 block into an S5, or S5 stuff onto an S4 block?
aka, is the ECU S4 or s5?

 

Got to http://www.rotaryresurrection.com/ and click on tech. You'll find your answers there.

 

You are actually doing an a$$ backwards swap......

 

nevermind what I wrote; I'm off in la la land. S4 block = poo compared to S5 block because of the difference in compression ratios. It is possible though....but try and stay with an S5 block

 

ok, im sticking with a s5 block, does anyone know where i can buy one cheap?

 

No, the S5 blocks are getting harder to find. Might try a local junkyard or the for sale section.