Rubber-Cal Nitrile

[bcgreen]

Anybody have a small piece of the Nitrile I could purchase?
All I see is a big sheet which would be a big waste as I would a small amount to make a O ring.
Thanks

[burgermeister]

McMaster sells 12" x 12" sheets for a decent price

They also sell O-rings, of course!

[bcgreen]

Originally Posted by burgermeister

McMaster sells 12" x 12" sheets for a decent price

They also sell O-rings, of course!

I am ready to order but McMaster is asking what durameter hardness do I want 50 or 60?
Will ask them about the O-ring, maybe they have a Nitrile 'O' ring which will prevent waste, just have to wait until I find out what hardness will I need to stop a crankshaft bearing oil leak.
__________________

[stownsen914]

McMaster has every O ring under the sun, they should have what you need.

[bcgreen]

Originally Posted by stownsen914

McMaster has every O ring under the sun, they should have what you need.

I am not sure if a 'O' ring would be better at sealing than cutting my own.
Here's a picture of what I am trying to replicate.

[bcgreen]

Originally Posted by burgermeister

McMaster sells 12" x 12" sheets for a decent price

They also sell O-rings, of course!

To add to the confusion: Buna-N Rubber # 8635K164 -20° to 170° F 800 psi

Buna-N Rubber #1890T14 Fabric Reinforced to maintain their size and shape under heavy compression -40° to 220° F 1,500 psi

[stownsen914]

Try Viton for a material

[bcgreen]

Originally Posted by stownsen914

Try Viton for a material

Do you think its better than the Nitrile for my application?

[stownsen914]

I thought I recalled that Viton has better temperature resistance. If you google, you can find reference charts showing the various options for seal / o-ring and their properties. One example below.

https://www.marcorubber.com/o-ring-material-quick-reference.htm

[bcgreen]

I think I will need to cut my own as I don't know the dimension.

[Henry Schmidt]

Supertec sells a kit that comes complete with everything you need including a history of success.

[burgermeister]

The case may see temperatures above 220F, so pick accordingly.

So the point of this is to glue , or light press fit, a sleeve over the nose bearing that then compresses a rubber seal against the case to stop a leak at the nose bearing O-ring? And the crank pulley bolt is used to create the compression until the glue sets?

I would use the softest rubber possible, and a narrower strip (1/8" to 3/16" wide) than what you have pictured, ideally 1/8" or thicker. If you have a lathe, cut a locating lip of some sort around the outside perimeter to keep the soft rubber in place. Shouldn't see much pressure, but just in case ...

Actually, one possibility might be a nose bearing O-ring. Somewhat soft, and we know it will stretch around the nose bearing ... not sure if it leaves enough gluing surface though.

[bcgreen]

Originally Posted by burgermeister

The case may see temperatures above 220F, so pick accordingly.

So the point of this is to glue , or light press fit, a sleeve over the nose bearing that then compresses a rubber seal against the case to stop a leak at the nose bearing O-ring? And the crank pulley bolt is used to create the compression until the glue sets?

I would use the softest rubber possible, and a narrower strip (1/8" to 3/16" wide) than what you have pictured, ideally 1/8" or thicker. If you have a lathe, cut a locating lip of some sort around the outside perimeter to keep the soft rubber in place. Shouldn't see much pressure, but just in case ...

Actually, one possibility might be a nose bearing O-ring. Somewhat soft, and we know it will stretch around the nose bearing ... not sure if it leaves enough gluing surface though.

I have now adjusted my quest to consider the 220. I will be using the crankshaft pulley bolt but cannot get my collar lip cut. So I cannot go with a soft rubber because the softer you go on the rubber the more likely it will squish out when the motor gets up to temp. I will go with a harder rubber (50A durameter hardness) and torque it down with out distrorting.
I have thought about the O ring but again it might be too soft and I feel going with a harder rubber will allow me to torque it down pretty good and should really seal down. What I am not sure is wrong with this idea of going with a harder rubber and torqueing down pretty good and what will happen to the sealant.

[burgermeister]

This is what I had in mind. About .050" of compression in the 3rd pic, applied with an arbor press. Collar seems to hold it.




You are welcome to the parts if you want to use them. I had a suitable ring sitting around ... not exactly the size I wanted but close enough...

[bcgreen]

Originally Posted by burgermeister

The case may see temperatures above 220F, so pick accordingly.

So the point of this is to glue , or light press fit, a sleeve over the nose bearing that then compresses a rubber seal against the case to stop a leak at the nose bearing O-ring? And the crank pulley bolt is used to create the compression until the glue sets?

I would use the softest rubber possible, and a narrower strip (1/8" to 3/16" wide) than what you have pictured, ideally 1/8" or thicker. If you have a lathe, cut a locating lip of some sort around the outside perimeter to keep the soft rubber in place. Shouldn't see much pressure, but just in case ...

Actually, one possibility might be a nose bearing O-ring. Somewhat soft, and we know it will stretch around the nose bearing ... not sure if it leaves enough gluing surface though.

Yes to your question about the sleeve and yes to the pulley bolt to create the compression.

How successful have you been at stopping the leak and if so how long did it stop?

BTW thank you for your generous offer and I will take you up on your offer once I fully understand your process.

I will be dropping the engine slightly so I can access the area so I can make a measurement as to what size O ring I will need

[burgermeister]

I never used this method - I just made the clamp ring after lunch to illustrate what I was thinking. It was a needed break from nonstop engine rebuild problems. Usually a clamp ring does a better job staying put than using 3 or 4 setscrews in a radial orientation. I sized it to fit a 3.2 / 993 nose bearing which came out of my engine. Not sure if yours is the same diameter.

Process wise, I would use a pulley bolt, ring & big washer of some sort to compress the clamp ring & O-ring against the case by about .050" (probably about 1 turn of the pulley bolt), tighten the clamp screw, and undo the compression mechanism, making sure the collar doesn't slip back. Then I would cross my fingers, toss some salt over my shoulder, what have you

It might work, it might not. I would advocate using some Curil-T on the O-ring and the case surface to help it work, ideally avoiding the nose bearing surface so the clamp ring gets decent friction.

I would send you the (used) nose bearing O-ring to go with the clamp ring. It is still nice and supple, I think it will work fine - or at least as well as anything else!

I feel soft is better than hard, as soft will conform better to any irregularities and it will compress a greater distance, which should make the seal more robust to any small movement of the nose bearing relative to the case that might occur.

PM me your address when / if you want me to send you the parts.

[bcgreen]

Originally Posted by burgermeister

I never used this method - I just made the clamp ring after lunch to illustrate what I was thinking. It was a needed break from nonstop engine rebuild problems. Usually a clamp ring does a better job staying put than using 3 or 4 setscrews in a radial orientation. I sized it to fit a 3.2 / 993 nose bearing which came out of my engine. Not sure if yours is the same diameter.

Process wise, I would use a pulley bolt, ring & big washer of some sort to compress the clamp ring & O-ring against the case by about .050" (probably about 1 turn of the pulley bolt), tighten the clamp screw, and undo the compression mechanism, making sure the collar doesn't slip back. Then I would cross my fingers, toss some salt over my shoulder, what have you

It might work, it might not. I would advocate using some Curil-T on the O-ring and the case surface to help it work, ideally avoiding the nose bearing surface so the clamp ring gets decent friction.

I would send you the (used) nose bearing O-ring to go with the clamp ring. It is still nice and supple, I think it will work fine - or at least as well as anything else!

I feel soft is better than hard, as soft will conform better to any irregularities and it will compress a greater distance, which should make the seal more robust to any small movement of the nose bearing relative to the case that might occur.

PM me your address when / if you want me to send you the parts.

Great. PM sent.

My engine is a 2.7, the same as the '73 RS.

If you never used this method what method did you use? I suspect you did a rebuild.

Tell me what you think of what I have mulled over in my mind? What might I have not thought through?
I think I have read every nose bearing leak and I was thinking that if I applied enough torque against a semi firm gasket, in itself would seal against anything. I was thinking a torque of 20 - 25 psi would work and a sealant would be there as an insurance.

Isn't there some sort of oil pressure outside of the nose bearing causing oil to be pushed past every ones attempt to stop the leak?
Your clamp ring has a opening, do you not think this could be the achilles heel?

[burgermeister]

While I have had a cornucopia of engine problems and oil leaks, I have not (yet) had a nose bearing leak. So I have not fixed one.

With an O-ring compressed into the case front and nose bearing outer, the clamp ring should never see any oil (assuming this strategy works) - so the gap doesn't matter. For reference, set screws would have the same issue - there would be a gap between the nose bearing and the ring.

You should measure your nose bearing diameter to make sure the part I made fits, or otherwise verify the nose bearing is the same diameter between your engine and mine (3.2 / 3.6), before I send you the ring - no sense wasting postage! I don't have a 2.7 engine, and I am not a Porsche historian, so I cannot do this.

25 ft*lb of torque on the crank bolt will generate thousands of pounds of force. This force is applied to the front of the case via a spring (compressed rubber). It travels through the case, the crank thrust bearing, and back through the crankshaft to the pulley bolt. None of these structures is designed for that kind of force in that direction.

Assuming nothing breaks, you then secure the ring to the nose bearing. First, the clamp ring won't hold thousands of pounds of force. Neither will set screws. Second, if they did, the force holding the rubber compressed would be from the case into the nose bearing and then nose bearing to the ring. The nose bearing to case interface is not designed for axial loads - all you've got is a little 5mm pin in soft aluminum, and maybe some friction. Something will move. Collateral damage may, or may not, result.

[burgermeister]

[boyt911sc]

Originally Posted by bcgreen

I am not sure if a 'O' ring would be better at sealing than cutting my own.
Here's a picture of what I am trying to replicate.

BC,

I mentioned this subject to Pat Keefe’s attention when was trying to solve the oil leak coming out from the nose bearing. The key to fixing this annoying oil leak aside from opening the crankcase is to find and use the correct sealant that would adhere strongly to the aluminum surface.

The aluminum collar and the nitrile rubber plus sealant would be more complex because you have now more materials to consider. A sealant that will adhere strongly to both aluminum and nitrile. Unlike in the previous scenario, only aluminum surfaces. Have you checked with those people that have done it successfully what sealant were used?

Or try Henry’s product. The key to your success is not the mechanical approach only but heavily dependent on the sealant’s properties. Good luck.

Tony