Every one says that teflon O-rings are far better then the stock oem seal between the combustion chamber and water jacket. My question is? Well, the rubber seal seams to be design for the groove; its square and shaped for a square groove. I know hundreds of guys are using o-rings but isn't that like sealing a sqaure space with a round ball. To me it seems like the hylomar is whats allowing for a sealed surface and the upgraded o-ring is a filler. I don't get putting a o-ring in a square groove specially teflon.

 

Haveing tried my first set of those in an engine this week, I can say that the idea (I believe) behind them is that they are oversize (in regards to thickness) versus stockers, and once the engine is tensioned they get pushed into square, with some material to spare, thus they seal a bit better.

 

As far as I know it is standard that when you machine an "O" ring groove into a piece you use a square edged tool and the resulting groove is square edged at the inner groove "shoulder"- just like the stock rotary water seal grooves.
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lOl --> Good
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If you machine a rounded "shoulder" "O" ring groove to match the "O" ring there is nowhere for the "O" ring to deflect to as you compress the "O" ring and it is squeezed between the (sharp) outer edges of the groove and the piece compressing it from above. This unduly stresses the "O" ring locally and if there is ANY movement in between the pieces it will shear the "O" ring.
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Basically, round "O" rings do usually go in square grooves for good sealing. Or yeah, what Kevin said...

 

So your saying the stock oem rubber seal is poor design.

 

No, stock seal design is good. The large rubber block will expand in its slot as it needs to compress the little amount it needs to w/ out "pinching".

Just saying- all the round "O" rings I have seen fit into square slots as well.

 

No, I wouldnt say that. IT is designed in a square pattern, a bit too narrow yet taller than need be. When tension is applied to the engine, they get compressed down and outward, and fill the groove perfectly, while making a seal on the top and bottom sides. They work fine.

These other seals, are perfectly round, and are oversized a bit more as far as thickness. When compressed, they fill the gaps that were previously left between their round edge and the square slot. I believe there is probably slightly more material there than the stockers have, so this makes them slightly stronger.Also, they are covered in teflon on all sides, versus the stockers which are only protected on the inner and outer edges.

 

The guys who o-ring piston engine heads will argue that the o-ring seals on 4 sides with higher seal compression versus a flat seal.

We use these teflon o-rings on all customer engines who opt for it.  We have had zero problems with the o-rings themselves.  One of the big pluses is that it's reusable.  It's also CHEAPER than stock OEM Mazda parts.


-Ted

 

So what is the commond failure of the water seal. Exclusing housing erosion. Could it be improrer torque, not following the torque seqence, Failure to apply hylomar properly, or pinching of the o-ring.

 

In my experience, it's been cracking/hardening. From overtemping. The teflon seals, have a higher temp tolerance.

PS anyone remember where to get them. I mean, the McMaster Carr part #'s?

 

http://fc3spro.com/TECH/MODS/ENGINE/...ING/tefsil.htm


-Ted

 

Hmmm....

SO kevin are all your rebuilds up to this point using stock seals? Maybe the next engine I get I'll opt for the ones you speak of.

 

What about that metal piece that suppose to protect the O-ring from the exhaust port. Should you still use it.

 

up

 

I would imagine you still should, erau. It'll still keep the heat away from the Oring.

 

i never hear people menion of it

 

I thought they came with the seals to help incase of corosion in the groove?

 

didnt they stop using the metal piece sometime in the 70's?

 

Don't know

 

well ive never seen it on an FC motor, only heard about it on older ones.