I just bought a bunch of s4 and s5 13b parts used and all mixed up. I'm building an s5 NA motor to swap into my FB which currently has an s3 13b (GSL-SE). I've never rebuilt a rotary so I need a little help

1. How can I tell the difference between an s4 and s5 front iron (NA)? I haven't found much info on this one.

2. Are my s5 irons useable? There are some spots that look like surface rust – can I clean them up or are they trash?

3. These are s5 rotors, right? The tub looks milled to me but I have nothing to compare them to.

4. The rotors have a little corrosion, especially on the bearings. Can I soak them in something or do I just need new bearings?

5. The eccentric shaft is trash due to the rust spots, right?

 

1. the difference between an S4 and S5 front iron is very small, essentially instead of milling it flat, and using water pump shims, its stepped to eliminate the shim. Casting letter is different, S4 should be an E, not sure what S5 is, my sheet is borked
2. put some 600 grit paper on a block and see if they sand out, if they do, you're ok
3. yep, those are machined
4. you might try cleaning the bearings, worst case you just use new ones, could be worse
5. again, try some paper, the E shafts are very good material, and usually they will polish out

 

After what the E-shaft I used in my current motor looked like before I cleaned it up I would say that one should be fine. Some fine emery cloth followed by some 600 and 1000 grit strips of sandpaper should clean that right up. You might not even need the emery cloth if that's the worst of it. Here was mine.




As for the irons if there's no pitting that won't sand out you may be fine. If so you might could lap them if it not too deep.

 

Thanks for the replies, I might be able to clean up the eccentric shaft but unfortunately there are deep grooves in all of the s5 irons I got, so I think they're all trash regardless. I can definitely catch a fingernail on them no problem so I'm sure it exceeds 0.1mm.

I'm also a little panicked because I found a scratch on an s5 housing which I missed until now. It barely touches the flat spot where the coolant seal makes contact. If this housing is trash, and the irons are trash, I just threw away a ton of money. Is this still useable?​​​​​​​