> >  >      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

   If that's the case I would see no reason to use them, I wander if
there is difference between the stick and the automatic rotors ??
  I will stop over at Rob Golden's shop as he has some RX-8 rotors and
I know he has good scales there.  Ken

I wonder that too. There could be a difference. Some of the guys are using
four axis NC machine tools to lighten the rotors internally.

Paul Lamar
 
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