Is there a difference in the S4 and S5 rotor housings? Also, is there a difference between turbo and NA rotor housings? Thank you!

 

Spark plug hole spacing and threaded embossment for the knock sensor and/or block heater in cooler climates on S5 and up. Turbo and non turbo housings are identical except for the exhaust sleeve and extra coolant hole on the turbo version.

 

Will I be able to run an S5 NA rotor housing in my 91 turbo motor?

 

Yes, just remove the exhaust diffuser in exhaust port.

 

Do i have to do anything about the coolant hole for the turbo? How will the turbo be water cooled?

 

In addition to the hole, there is also a counterbore for an O-ring. You'll need to get a machine shop to bore that pocket into the housing. That feature usually makes it tricky if you're **** about matching the configuration of your original setup. Check the 'For Sale' section. You might find a forum member who has exactly what you need.

 

Im used to FDs so I apologize that I didnt take the coolant port into consideration. The above poster info is correct. Sorry for the mis information.