Do I have a S5 or S4 waterpump housing ? Either way, are they interchangeable ?

 

Pretty sure thats the S4. The thermostat housing has 2 bolts, correct? The S5 thermostat housing has 3 (?) and uses an o-ring instead of a gasket.

As far as interchangeability goes, Ive heard that the angle of the lower rad pipe is different and can interfere if you have mismatched front covers and pump housings. I cannot verify that this is true, and I cant remember which one has a steeper angle. Anyways, hope this helps!

 

Yeah, my thermostat housing has two holes.

 

Yeah, then it is definitely the S4 housing then. Iirc, the S5 housing will fit on a S4 front cover, but not the other way around. Where did you get that badass t-stat cover, btw? It would work nicely for my new Afco dual pass

 

The previous owner did it.

The housing, thermostat and cover is actually for sale right now. Someone who asked about buying it, wanted to know if it was a S4 or S5.