> Hi Paul,
    > I'm enjoying following along with your current threads!!
    > Hope you don't mind me chiming in here again to ask another newbie
    > question:
    >
    > I've been slowly acquiring S5 NT (9.7 : 1) rotors for my 20B NA
   project
    > (much cheaper that RX8 rotors).  I had 2, and just received the
   3rd one
    > today.  I've been trying to be careful to make sure I get rotors with
    > matching weight code stamps, but the one I got today is
   different.  Can
    > you help here?  I hope you don't mind me including pictures!!  I
   tried
    > to make the files small.  The first 2 pics are the rotors I
   already had,
    > and they show a "C" along side another weird symbol (kinda looks
   like
    > a 7).
    >
    > The next pic is the rotor I got today.  It shows a "C" along side an
    > "E" :
    > My question is.......Is it OK to use all these rotors together?  Are
    > these all S5 (9.7 : 1) rotors?  Is this last rotor a weight code
   "C" or
    > "E" ?  What's the other symbol of Letter mean?
    >
    > Thanks again for all your help and knowledge!!
    > Don
    >
    > From what I gather you can't mix and match weight codes.
    > I think you need to have it balanced by an experienced
    > rotary engine balancer. The rotors must be balanced
    > about their center point and matched with all the other rotors
    > for weight and then the counter weights adjusted
    > for the exact weight of the rotors. There is a guy here in
    > So Cal that does it.
    >
    > Rotor weight codes.
    > The only thing I can find is this.
    > http://www.rx7club.com/showthread.php?p=1309602#post1309602-
    >
    > I'll forward this to Jim Mederer. Hopefully he will have time
    > to help as he gets the really hard questions :)
    >
    > Paul Lamar ...No rotor no motor.


   Hi Don;

   These all appear to "C" weight rotors.  For a 2-rotor, letter codes must
   be adjacent,
   e.g. B/C, D/E, C/D are OK  (A/C, B/D are NOT)
   The rotors themselves are balanced about their centers at the factory.
   I am not sure what the balance requirements are for a 3-rotor.
   I believe the backwards "E" and other characters are Japanese - don't
   know what they mean.
   Theoretically, the S5 rotors weigh the same as the 20B rotors, and you
   "should"?
   be able to use the 20B front and rear counterweight without rebalancing.

   I posted some rotor/balance info a few weeks ago.
   The S5 rotor faces are machined, the S4 have a rough cast appearance.
   You could also measure the depth of the combustion area.
   See attached file
   -> might be worth adding to the website.   I don't have any turbo stuff.
   A couple of housing comparisons might be useful as well, I'll see what I
   can scare up...

   When mixing and matching parts for higher than stock rpm, a custom
   balance is not a bad idea.

   Cheers
   Cary


Thanks Cary,
This is what I have:

All are machined faces.
Thanks,
Don




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