Your bad info is stating Dow 55 is bad for Viton o-rings, and that Henry is omitting inportant info in his reccos. You post a chart from another manufacturer dealing w/tensile strength, when that is a non-issue in compression of an o-ring.

I'm done with this, and Henry certainly can speak for himself. Many, many here have benefited from Henry's advice, and I presume many more will in the future.

You, have NO credentials here to justify anyone heeding your warnings.

I used Dow 55 on Viton packings even aware of the loss of tensile strength because the packing in use of sealing through bolts is under a compressive stress.

You're a bit crossed up on your facts.

Facts:

1) The chart isn't from another manufacturer. It's from DOW... Who manufactures DC55. Go figure!
2) DC55 reduces tensile strength of viton by nearly 50%.
3) DuPont Krytox GPL-207 is inert and birthed the mil spec.
4) This information wasn't provided in this forum until I brought it up. This is then "new" information as of nearly 3yrs ago now.
5) The sharp edge of the thread on the bolt is present in the joint, even with chamfering of the case.
6) Henry, and this thread, recommend DC55 without mentioning the requirement of machining the case. (Opinion alert: I believe this fact is a problem).
7) Krytox GPL-207 which I suggest as alternative and doesn't reduce the strength of the o-ring.

If you don't find use in facts it doesn't mean others won't. Some people still voted for Clinton after all.



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Oh wow, you all of a sudden convinced me you're the person to listen to. :rolleyes: You're the new expert here. :rolleyes:

Lapkritis,
A small chamfer on the block keeps the o-ring from being forced/crushed into the threads by the chamfered washer. AND it can also help to prevent the o-ring from being crushed by the washer, causing it to come out the side as seen in the other thread "Your opinion wanted. Green bolt through viton o-rings with rtv. The o-ring has a tendency to walk itself out; this helps keep it in place.

I too have used Henry's sealant methods for rebuilding my own engine.
I really appreciate the fact that he shares, what I would consider, trade secrets.

The fact is, most of us folks on this forum, are newb's at this.
If Henry said, "Ya, just use some peanut butter instead". LOL!
A lot of us would probably say "Oh wow! So what brand should we use!"
No questions asked!

Henry has a lot of experience, and most of us look to that.
We can't afford to necessarily try new ways to do things.
We just want to get it done right the first time.
It might sound pathetic, but it's a fact.

i read this thread , and other threads. I thought about it. And used my experience to conclude the case chamfer is critical for success.

Easy to do with a chamfer bit and a hand drill. This should be done.

At this point in time, I'd think anyone looking here would get the idea that the chamfer on the case, combined with the factory washer with the chamfer is the right way to go.

I know the o-ring is in compression when the through bolt is torqued. Swelling to better fit a proper double chamfered joint is good. Especially because the swelling occurs in time, after the joint is torqued and the washer is in direct contact with the case, without o-ring material crushed in the joint.

Quick hits guys such as yourself are the ones who will benefit from using the list after it's updated. It's inadequate now because it lists a grease that weakens tensile strength but fails to list the requirement of machining the case. Imagine mixing the worst tensile strength grease/seal in the sharpest joint... Then imagine the strongest grease/seal in the smoothest joint. Only the first condition includes DC55.

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But now the list is complete:

1) you should chamfer your through bolt holes, if they were not installed previously

2) Dow 55 will work well with green viton o-rings when mated with chamfered holes.

3) green viton through bolt o-rings still seem to be the best.

So we have updated, and captured the knowledge! 🍻

4) Krytox GPL-207 offers roughly double the tensile strength over DC55.

Then you're done.

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I agree. Done!!

😀

As the father of this thread (OP) I would ask you to leave political references for off topic. This is about engine sealants that are empirically proven to work. To that end, I've put the advice Henry has provided here in practice on quite a few engines. They don't leak. Your histrionic, near nonsensical posts on "omitted" information are just cluttering up my thread. Stop.


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Hello,

I'm rebuilding my 964 engine, can anyone tell me if the DC55 can be used on the 'red' through bolt o-rings that are included in factory Porsche gasket sets? I'm not sure if they are Viton.
Also, I have purchased Henry's kit, are any of the products suitable for use on the factory Porsche 'black' cylinder base o-rings or are these only installed dry?

Thanks in advance.

I don't recommend installing any o-ring dry. Others will chime in on whether this lube or that lube is best, but the important thing a lube does is allowing the o-ring to settle in its place without pinching or distorting allowing unequal sealing between the surfaces it mates to. Also, not a lot of lube is necessary. Just enough to make the surfaces glassy in appearance will suffice.

On VW AC engines I've done dry with hit or miss results, same for oil.
Then switched to teflon pipe compound, worked, but I never liked it.
Once I switched to the Dow product I never looked back on both Porsche and VW.

Sealant on an O-ring is a big no-no, don't get me started on RTV....

The one big trick is to deburr all holes and surfaces, one nick and you will have a leaky O-ring.

With regard to the red o-rings, I would echo the warning by DOW itself against use of DOW corning 55 molykote.

From DOW:

Source is spec sheet on product site:
http://www.dowcorning.com/applications/search/default.aspx?R=392EN


No compatability concerns with Krytox... It's inert.

Strength of Materials........
 

Lapkritis,

Not sure if you are a technical guy or what, but you seem not to understand what is tensile stress or strength. The o-rings at the thru-bolts don't experience tensile stress. They are under compression. Yet, you keep telling us about tensile stress. Hope you have some accredited units in Strength of Materials Testing. Some of us here have. A guy read a technical article and suddenly becomes a guru! Research the technical definition of tensile stress in your Chemical or Mechanical Engineering Handbook.

Tony

I haven't until now typed the phrase "tensile stress", nor discussed it. The simple metric relation to tear resistance is the basis of the discussion. Put a sharp edge from the bolt in and that's the point. Pun intended.

We have used Dow 55 o-ring lubricant on every o-ring in the air-cooled 911 engine for over 15 years with zero failures do to deteriorating o-rings.
Every o-ring failure we've encountered all 3 of them (out of thousands) have been the result of errant installation. No one is perfect.
I endorse Dow 55 because it has proven to works flawlessly. No conjecture from an angry troll, just proven observation.

Complacency kills.

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^^^^
"If it ain't broke, don't fix it."