GPL 207 is the preferred flavor. I also use this on the oil return tube, distributor, oil cooler and other rubber ring seals. There are many forms of Krytox out there with various properties... this one is suitable.

Timely thread for me. I haven't really started assembly yet on my '84 3.2l but I checked the case last night and I only have chamfers on one half of the case as well. I ordered the tool from McMasterCarr and will take care of that before I assemble.

We use the Dow 55 for two main reasons.
First, the Dow is a Phenyl-methyl silicone grease formulated for O-rings with properties that add a slight seal swell for increased sealing of rubber (including synthetic rubbers) to metal surfaces.
Second, silicone based products like Dow 55 resists the capillary action or wicking that can occur when white grease is used to seal petroleum based oil products.

Henry,

Are you using this Dow Corning 55 Molykote?

http://www.dowcorning.com/applications/search/default.aspx?R=392EN

I know they have different flavors but see this carries a relatively low temp rating. Would like to compare to the Krytox specs.

Dow 55 in a 5.3 oz. tube is on sale at Grainger for $6 on clearance. And then newgrainger.com opens and it's gone.............

No, we aren't using commercially available Dow 55 Molycote. We're using a mil spec product directly from military suppliers.

As to your question: what specs do you believe Krytox has that are important to this application? I'm wondering what function you think a lubricant in this application (o-ring that seal engine oil) performs?
That question was awkward so put another way: why are we (engine builders) putting anything on an o-ring?

I was going to put the spec sheets side by side. Not commercially available you say but yet you sell it making it... commercially available. Is that right?

My answer to "why are we (engine builders) putting anything on an o-ring?" is:

To keep the o-ring from becoming compromised during installation. This would include ripping, tearing, or pinching the o-ring when assembling the parts. The lubricant allows the o-ring to move instead of stick on the surgically clean dry surfaces that we have prepared prior to assembly. Without lube, it would be all too easy to damage the o-rings and prevent them from functioning in their intended purpose (to seal oil in and dirt out).

just my $0.02 (like I said before, use what works best for you. The opinions here are just that, opinions, and your mileage may vary.)

Why so combative?
The truth is, I don't sell it. I buy it in large quantity container that makes selling it impracticable. Much like most of the products I make, I made them because I needed them for my projects.
I needed a high quality o-ring lubricant so I sourced the best I could find for the shop. It works well so a add a small amount (literally a little baggie) to my sealing kit as a favor.

Johnman: You are absolutely correct "To keep the o-ring from becoming compromised during installation". After the o-ring has seated, the lubricant has done it's job and any product that can cause a capillary action or wicking is counter productive. That is why we avoid white grease and petroleum products in these applications.

I'm not combative, but I would like to compare the materials by the data sheets. Why aren't you forthcoming? Just curious.

I used Dow Corning Molycote 111 (because it was the o-ring grease I had) on my ongoing rebuild for the o-rings. That wasn't a mistake I hope?

No worries Magnus, Dow 111 is primarily a Silicone-based compound that resists wicking and has been used by many people on this forum with success.

Thanks, good to hear!
They did go in quite smooth.

I used the sealing kit from Henry with the green viton O-rings and the Dow 55. Unfortunately I had the through bolts on the wrong side, and decided to reinstall them on the oher side, for purely cosmetic reasons. Some got damaged in the process, and I can see one that did excatly what the OP shows in the picture.

Now I still have the blue O-rings that came with the case sealing kit. Can I use those with the Dow 55 or are they going to be worse than the green ones?

The issue is the same with my SC case: the bores are not chamfered. So does this mean that the blue rings are similar to OEM (harder?) and will work better in my case?

The blue o-rings were designed for a different sealing/washer system. They are very soft and under similar conditions will show even more damage (less chance for good sealing) than Viton o-rings. You're always taking a chance if the case holes are not properly chamfered.

Or you could just lather on some more lube, that ought to do it.

;)http://forums.pelicanparts.com/uploa...1376092374.jpghttp://forums.pelicanparts.com/uploa...1376092445.jpghttp://forums.pelicanparts.com/uploa...1376092550.jpg

Just thought our O-ring guru would like to see what a properly cleaned engine looks like before reassembly...

Metal masturbation.

So the Dow 55 Silicone grease:

1) Weakens rubber tensile strength tremendously.

2) Causes rubber to swell greater than 10%; Viton actually will shrink. Common application is for temporary relief of gearbox leaks.

Keep slapping it on there though. I sure as heck wouldn't.


See for yourselves:
http://www.cibsupply.com/pdf/dc55.pdf

Henry, would you have a nice pic of a "properly chamfered" case hole?