Well, as I was tearing apart and planning how to rebuild my motor I found out some interesting things that I think are important to share. Here are some of my findings on my own or in speaking with others.

• Cosmo rotors are the same as FD.
  
• Rotors have a balancing code on them. If you look closely you will see a small letter stamped on the rotor. There may be a few but you should see two matching letters. You can swap for a different rotor with a letter only ONE letter away. i.e. A with B but not A with C.
  
• This one I am not 100% sure. You can use any rebuild kit with 86+. Only differences are in the exhaust gaskets and maybe front cover gaskets. Example, I know I can use an S4 internal kit for my Cosmo with an FD center plate.
  
• This one is from a poster on this forum. S4 rotors have cast bowls whereas S5+ have milled.
  
• Cosmo S6 housings can NOT be swapped front to back when stock. The front housing actually has a lower bolt patter for the exhaust manifold. If you line your two housings up the front should have a lower bolt pattern than the rear. The casting may also look to be lower. There is also a very small line in between the spark plug holes on the right side of the housing. My front had a red line whereas someone elses had a blue line. Mike (j9fd3s) also told me it is because of the air injection not lining up.
  
• S4 and S5 did not have different patterns so they are interchangeable.
  
• You can use any S4+ rotating assembly in any S4+ engine. i.e. S4 rotors, e-shaft, BOTH counterweights in an S6 skeleton.
  

That is all I can think of right now.



Please add your own thoughts and correct me if I am wrong.



Eric https://www.nopistons.com/forums/pub...IR#>/bigok.gif

there are 4 "generations" of rotaries

1968-1974

1974-1985

1986-2002

and the renisis.



the 1986-2002 engines are mostly compatible, ie they use the same water o rings apex,corner, side, and oil seals. the major differnces are rotor wieght, compression, porting, and engine mount location.



the 89-02 rotors are all the same wieght

the cosmo engine have the largest ports, followed by the fd and then the t2

the fd and possibly cosmo (the parts have cosmo #'s) use better bearings





mike