ok guys hi, it's an 88 turbo II, needs rebuild now can i put the s5 rotors in the s4 engine?? would it be a perfect fit?? i know there r lighter, ecu im gonna upgraded to a haltec problably so i dont need the s5 ecu. any other thing in the engine other then the rotors that i can change that would help me?????
P.S i've searched before asking the question by the way in the forums. =P i just got an 88 turbo II but engine needs the rebuild

 

use the entire rotating assembly:
S5 rotors
S5 E-shaft
S5 front and rear counter wieghts
S5 Flywheel

Given the wieght of the rotors compared to the series 4, you must use all the corresponding lighter S5 components to keep it all in balance

 

Exactly. But the differences aren't that huge. If you plan on running alot of boost I'd stick with the S4 rotors. My friend uses S4 TII rotors in his FD with 28-30 p.s.i of boost. The difference isn't that much however. 8.5 to 1 ratio on the S4 and 9.0 to 1 on the S5. FD rotors are just the same as the S5. I'm using an FD flywheel on my '89 GXL.