I want to use s4 turbo rotors with S5 NA front housing and S6 rear housing in my build. What do I need to use for rotating assembly? Can I use my S5 NA E shaft and front counterweight? Or do I need to swap to an S4 front counterweight ?

 

if you want to use the S4 rotors, then you need the S4 counterweights too

 

Shafts are fine to swap, the same generation counterweight must stick with the same generation rotors. The housings are slightly different in their makeup and small changes but can be interchanged relatively easily.

 

Thanks guys. Do you know if I can use a 12A front cover with a turbo build ? This is going into a 74 RX4 . front cover has the engine mounting which I would like to retain if possible.

 

I hope you're eliminating the port wing in the n/a housing. I've seen weirder things in builds before.

 

you can, the metering pump is a different bolt pattern
and then the turbo drain is different.

if you have an 83-85 12A front cover the casting is there, you just tap it out
if its older, you're on your own

the factory oil drain for a 12A turbo looked like this

 

Super helpful info. Thank you. Think I will just buy new S5 turbo rotors and keep my rotating assembly the same. Wish me luck

 

What's more important new rotors or new housings? Should i spend more money on new housing and get used rotors or vice versa ?

 

Rotors can get sloppy but rarely do they get worn to the point of being a major issue for a rebuild. I've even seen 200k+ mile rotor apex seal slots still ok to reuse. Rotor housings are where most of your compression issues come out. You can seal up a used rotor pretty well with new seals, you can't replace missing chrome on a rotor housing. Resurfaced housings also don't last as long.

If it were my engine and had the choice i'd do housings. since rotors cost nearly the same.

Just don't mix up rotors if possible, a rear rotor will wear the slot V shaped in no time after moving it to a front rotor position, now turning backwards. You can usually tell where it lived in an engine based on the lip it formed at the rotor tips.

 

i'd prefer new housings, but you might measure everything first.

 

Is there any downfall to using one used housing and one new housing? The one S5 housing I have is in very good condition. No marks or chrome shipping or chatter marks. very smooth and nothing felt with finger nail.

 

not totally, though most folks if they're dropping nearly $1k for a housing would drop $2k for both housings to make everything equal. if the old housing is in very good condition, your compression shouldn't suffer a whole lot. a straight edge and a flashlight on the backside can tell you the truth about a rotor housing.

compression differential allowance is roughly 15% from one rotor to another, but in turbo engines you have to compensate for that with your tune since your wideband readings will actually be an average of both rotors, while one is working slightly harder. rotaries are already unforgiving beasts and im tired of keeping my secrets.

 

Is this a typo? Wouldn't a S6 be a 3rd gen or FD housing? If so and not a typo I don't know of an intake that would bolt to this engine as the FD's intake manifold bolt pattern doesn't match the older engines nor would any of its ports match right. Anyway, hope it was a typo, and you meant S5.

 

pretty sure he meant rotor housing, which the S5 and S6 share the same port shape and spark plug timing though the n/a has a winglet in the exhaust for noise diffusion.

even the most redneck builds i've seen i have yet to come across someone mixing n/a and turbo irons. as you said, the intake won't even bolt up.

 

Yeah S5 and S6 housings will work together. Apparently S6 has stronger different coating than the rest of housings and they're easier to find.. Thinking I'm just going to find a good used one though. Buying new is having me want to buy everything new.. and doing the math in my head everything is going to be " while im there might as well get new" . easy way to spend 10 k

 

For some reason I read your post wrong and equated rear housing to rear iron. Never mind. S6 rotor housing should be fine in the rear.