I've seen the rotors touch on rx-7s limited to 8k rpms.



I have my suspicions as to what caused it though...

great info lynn, does this have much effect on the oil scrapers? since theres .012" less on one side? interesting on the thrust faces i would have never thought of that https://www.nopistons.com/forums/pub...1047683894.gif much appreciated

No machining in that area at all. The grooves are left stock. The thrust face on one side is part of the timing gear. When you lay a straight edge across the rotor faces, the proud land area (the widest part of the rotor)is the thrust face. It seldom touches anything so many have no wear marks. Normally the side seal and corner seal spring pressure keeps the rotor centered in the space.



Lynn E. Hanover

Thanks Lynn.

cheers!

And again today, another engine which was limited to the stock s4 redline...

ive seen that too, we thought it was the gear coming out, although it could be oil pressure related too, stock 89-91 redline, 8250....



later with more oil pressure, we were revving a junkyard engine to 9400 with no troubles....

I forgot to point out that before measuring the thrust face, press the gear into the rotor solid.



If it has wear marks on it press it in. Then run a DA (orbital sander) over it to take out tooling marks and give it a dull finish, so touching will shine it up so you can tell when it walkes out again.



Or,



You can drill three holes that involve a bit of the gear and the rotor the tap size for a 6-32 socket end headless screw. Tap it and screw in a screw to the botom and stake over the hole. Gear never walks out again.



Lynn E. Hanover

Thanks a lot for the great tips Lynn!!! Now I gotta get these things over to the machine shop and make it happen.

This can happen on motors that run too hot. The bearings work on the principle of a hydrodynamic wedge. Being that these motors are always in the power stroke it is important(crucial) to keep that wedge. This will start to break down once the heat starts to get over 200 degrees. When that happens things start to move around in ways they shouldn't. That is where higher oil pressure combined with a adequate cooling is important over 4krpm. Not saying you not aware of this just putting the two statements together for others to read.





-S-