>      Subject: RX8 Parts

      > George Lendich wrote:
      >
      > Paul,
      > Interesting conversation I recently had with the local
engine builder on RX8 Parts and their interchangeability with the
RX7.
      >
      > He recently built a RX7 racing engine with RX8 rotors - I
thought the RX8 rotors were quite a bit wider ?
      > I also thought the bearing sizes were different - but
apparently not !
      > Anyhow all went well until he got to 10,000 RPM when the
rotors were binding on the endhousings, so they shaved (just a
little) off the sides of
      the rotors.
      >
      > He also noted that the rotor side seals were much shorter(
in length) that RX7 side seals. He was concerned about too muck
leakage but they worked
      OK he can
      > only put down the extra gap in the side seal ( to the apex
side seals) as needed because the side seals were exposed to
greater heat of the side
      exhaust and
      > therefore expanded more!  Apparently some people put in
bigger apex side seals to make up the difference in gap.
      >
      > Also the apex seals were shorter in height so they cut the
slot deeper and put in Hurley apex seals.
      >
      > Speaking of Hurley apparently they have a 2 piece side
seals ( very thin) which are very flexible and tough.
      > I suggested using a bi-metal hacksaw blade and grind it
down to size as they are very flexible and tough - the new hacksaw
blades out now don't
      break at all.
      >
      > Cheap side seal idea if anyone wishes to try it.
      > George (down under)

-> "Powell, Ken" wrote:

 George, great info.  I have wondered if you could use the rx8
rotors in an earlier 13b.  The lighter rotors would allow us to
turn higher rpm safely.  If you
 are using a PP intake port this sounds like a less expensive route
than a new rx8 engine.  Looks like you would need rx8 rotors,
seals, and front/rear
 counterweights to make this work.  Maybe the 86 - 91
counterweightes can be used if the rotating assembly is balanced.
Does anyone know if weight would have
 to be added or removed from the counterweights to work with the
new rotors (seems like the weight would need to be removed from the
counterweights to balance
 lighter rotors but sometimes things don't work like it would
appear at first)?

 Ken Powell-

Dave Atkins had a 1993 3rd gen and an RX8 rotor at OSH. The appear
to be the same weight.

   The apex seals are shorter due to the fact that the exhaust ports
would gas charge the back side of the seals and warp the springs.
   I have had the same thought that if you use them on 13b side
housing that you could turn higher rpm due to the lighter rotors and
the higher compression ratio and you could cut the apex seal groves
out deeper for the early ones better support.

   Ken

At this time I don't think they are lighter Ken.

Paul Lamar
 
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