John Gibbons I have a suggestion with regard to the o-ring splitting
problem. Were these o-ring in housing engines or were they perhaps o-ring in side plate? If so were the plates surfaced? If the grooves are too shallow splitting along the length wouldn't be surprising. Bill Jepson
The O-ring are mostly in side plates.
The O-rings are sized for the depth and width of the slot. That is if they are the proper dia. The .093 fits the best.
Read: http://www.rotaryeng.net/O-ring-size2.html or the pdf. Here is the chart from that page.
Paul Lamar
Paul that is my point on the depth of the o-ring groove. If the engines
in question had been re-built, (which sounds very possible). The side
plates might have been surfaced. If so the grooves may be too shallow.
This could cause the o-rings to fail, even if they are the right size.
If the TES o-ring was near the top size it might fail in a shallow
o-ring groove. Just throwing that out there. A lot of people might fail
to re measure  that groove when getting back their fresh newly finished
side plates.
Bill Jepson

Resurfacing rarely takes off more than 3 thou as that gets through
the nitride layer. In fact taking off .003 is not recommended as you will
have more than O-ring problems.

The Mazda slot depth is .063 by .145 wide. I just measured it again. There is some
rust and crud in the bottom of my slot so if it were cleaned properly it should be slightly
deeper.

Looking at the dwg. there is plenty of area for the O-ring to expand into even if
the slot depth is reduced to .060.

Here is a dwg to give perspective.

Normal squeeze called out by Creavey is .025" for this O-ring .093" -. 025" = .068" deep
so we are within .005" of the correct depth. Incidentally this is the tolerance
on the O-ring section diameter. Could be .088" dia.  or it could be .098" dia..

If we started with a .080" dia. O-ring the squeeze would be .080" -.022" = .058" deep
That is too low for our .063" deep slot. Not enough squeeze.

Paul Lamar ...No rotor no motor.

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