Trying to find parts right now, what are the options for rotors and housings?
S4 different than S5 for both rotor and housing? how about S6?
how important is front and rear, they look the same to me other than the tiny "F" and "R" on the top of the housings.
What do the letters stamped on the rotors actually mean?
Also dropped my front iron off at A-Spec tuning hoping that they can weld the small section at the coolant seal, if they will do it.

 

for the rotor you need an S5 NA one, some people will say that the letters refer to the balance weight, which they do, but they were graded by batch, and the batches vary, and any rotor made after 1991, is magically a C weight rotor.

so you can use any S5 NA rotor.

the F and R on the rotor housings are front and rear, the only difference is the air injection passage, they only drill it on one side, so if you put an R housing in the front it will block off the air injection, and it'll fail smog. unless you drill the hole. there is a little triangle chamber by the exhaust port, one side has a hole, the other wont, if you swap housings drill a hole on the other side.

 

I saw those when cleaning the housings and had no idea what they were. So I dont need this for smog but still need air pump for aux ports. if I use to R housings, will it damage the pump having it blocked off? or just flow a bunch on the other housing?
Are there differences on front iron from s4/s5/s6?