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Rotary Tech - General Rotary Engine related tech section.. Tech section for general Rotary Engine... This includes, building 12As, 13Bs, 20Bs, Renesis, etc...

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Old 09-17-2015, 08:31 PM   #1
Pete_89T2
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Default Oil Control O-Rings - which are better?

Subject is the general question - I'm leaning towards just using the stock Mazda OEM O-rings on my build, because they are a well known entity and have a durability track record. But there are a few aftermarket options out there too, e.g., Atkins Viton rings, and similar Viton rings that can be sourced from McMaster-Carr and elsewhere.

Was curious on what the experienced builders are using and why? Pros & cons of using stock Mazda vs. a specific aftermarket alternative?






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Old 09-17-2015, 08:49 PM   #2
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Silicone has a slightly higher heat tolerance than Viton.
Viton has superior resistance to petroleum products.
It's a toss-up between the two.

Silicone tends to swell when exposed to oil.
This is why you find "sqaure" o-rings on long mileage motors.
Viton tends to keep it's shape better under exposure to oil.


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Old 09-18-2015, 08:01 AM   #3
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Stock because I bet a lot more R&D went into them, like 40 years worth.
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Old 09-18-2015, 01:43 PM   #4
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^ What he said. Also, I've never had a failure with the stock green rings. Lastly, I've had a couple customers provide alternate rings from various sources and they never fit correctly. Just like the coolant o-rings, I always say, if you're burning up o-rings, you have a bigger issue than the o-ring material you used.
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Old 09-18-2015, 07:42 PM   #5
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Just a data point...

I've seen the green silicone o-rings disintegrate.
This was on a very high mileage 13B engine - over 200,000 miles.
The green silicon o-ring cracked into little segmented pieces - about an inch each section.
Each piece could be then squished between your fingers; the consistency was like a piece of cheese.

We ended up with the car with unknown history.
We can't confirm if the engine had been overheated.
We can't confirm if the engine has been frozen - this was in Sacramento, CA.

The engine was torn down because of excessive oil smoke, especially at higher revs - a sure sign of oil control ring failure.
This was a non-turbo FC.
All other seals were intact - water jack o-rings, inner and outer.
Almost everything else internally looked okay.
We replaced soft seal and apex seals (which were all under spec) and put back the engine for the rebuild.


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Old 09-18-2015, 08:03 PM   #6
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It was running Mazda OEMS and they where fine after the whole maybe 2k miles.
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Old 09-19-2015, 06:12 AM   #7
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Thanks for the input guys, I'm going to stick with the Mazda rings.

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It was running Mazda OEMS and they where fine after the whole maybe 2k miles.
I probably could have reused those rings; they still looked & fit like brand new... But my general rule of thumb on rebuilding anything is if it's a soft/rubbery part, chuck & replace it. That plus I may have nicked them while removing for cleaning the rotors/metal rings & springs, or may have exposed them to cleaning solvent during the process.
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