Case Sealant - #8 Main Bearing

[DavidPorter]

I have read many threads on case sealants. I have a specific question about the Henry Schmidt 4-glue recommendation from the thread on March 29. He says "we use ThreeBond 1104 and 1211 for perimeter sealing on the case (1211 on #8 main bearing). . .".

Does this mean use 1211 on the entire surface where the #8 bearing meets the case, or just the area around the o-ring, or what? I know this can be a trouble area for leaks, but will sealing off the the o-ring do the trick?

I could ask him but then I wouldn't get the full Pelican treatment.

Thanks.

[spydr32000]

Dave, I use Threebond 1211 on the case halves as well as around the nose bearing (no. 8) a small bead around the outside of the bearing is sufficient. I also use it on every joint in the engine. It keeps the oil where it is meant to be! Great stuff!!

[stevepaa]

I would never put a sealant on an o-ring or in the o-ring groove as it will inhibit th o-ring from doing its job. Apply a little on the edge of #8 if you like. I used the green Kuril

[ChrisBennet]

Originally posted by stevepaa
I would never put a sealant on an o-ring or in the o-ring groove as it will inhibit th o-ring from doing its job. Apply a little on the edge of #8 if you like. I used the green Kuril

I think the #8 bearing O-ring is the exception to this rule. I asked Henry to clarify this because it goes against what I've learned about O-rings. Basically, the #8 O-ring doesn't get the job done reliably so the sealant is used as the primary sealing mechanism. The O-ring is left in the motor but the sealant is the primary sealing mechanism. The sealant will compromise the effectiveness of the O-ring but we aren't really "using" the O-ring anymore so that is acceptable.

Now if we're talking about not using hardening sealant on the thrubolt O-rings, I'd agree with you.
-Chris

[Rex Walter]

Chris,

Please - one more time - I'm about to seal my first case halves. Walt has told me to use Curil T on #8 bearing. How much? Do I put only on the outside of the O ring, or do I try and get all sides of the O ring?

Rex

[ChrisBennet]

Originally posted by Rex Walter
Chris,

Please - one more time - I'm about to seal my first case halves. Walt has told me to use Curil T on #8 bearing. How much? Do I put only on the outside of the O ring, or do I try and get all sides of the O ring?

Rex

I don't want to sound like an authority on the subject because I'm not. For what it's worth I spread the sealant on the case halves around #8 instead of putting it on #8 bearing itself.
Put it on thin like suntan lotion. Remember, the case should almost be oil tight without sealant.

Test fit the crank and the case (dry). Getting #8 bearing to fit over the pin can be a little tricky. If you didn't clean the old sealant out of the perimeter bolt holes, it will scrape out and fall onto you the sealing surface when you mate the case halves. Now would be a good time to double check those holes...

-Chris

[Bobboloo]

In my opinion the #8 bearing O-ring is a bit of a design flaw.

O-rings are designed to be flexable and compress within an area slightly smaller than the o-ring itself. For this reason adhesive usually isn't used because you want the o-ring to seat itself.

Usually O-rings mate 2 surfaces that are parallel to the o-ring. In the case of the #8 bearing the surfaces coming together are 90 degrees (perpindicular) to the o-ring and even with oil on the o-ring it's very difficult to get the o-ring to seat properly because the edge of the case grabs it and crimps it a little when the cases are mated.

The idea behind Curil T is that it doesn't set up. It stays flexible like they O-ring and allows it to seat as well as possible and hopefully fill any voids left by crimping.

[adomakin]

this how i used it on the no. 8 as per henrys guidance. i was on the phone to poor henry like four times during the case close. (he must be sick of this english bloke phoning him up all the time!) very very helpful guy though. oh and please, i dont want to hear if its right or wrong, the case is closed , its taken me about 18months to get this far so if it leaks, £uck it. ill live with it!

[DavidPorter]

That looks like what I had in mind. Sounds like you're on the same time schedule too. Good luck.

[adomakin]

dave, a word of advice if you are about to close your case. get a mate round. i thought id be comfortable just doing it myself and then a mate asked if he could come round and watch/help. thank god he did-we started at 8pm and finished at 1am!

[blue82coupe]

Andy,Is that Three Bond 1104 or 1211 on the case perimeter. I'm in the process (slow) of sealing my case. My biggest fear in the build-up is case leaks. Dan

[stevepaa]

The only place I put Curil was on the area rearward of the o-ring groove. I put o-ring lubricant on the o-ring. I am trusting the o-ring and put Curil as a backup. I have not yet got the engine in the car. Maybe both ways will work.

Yes, and get help putting it together. good luck

[adomakin]

Dan, that is 1211. its more of a silicone type product. the 1104 performs like more of a solvent based sealer/adhesive

I was (am) paranoid about leaks, along with every other part of the build but after talking to people like henry schmidt at supertec and steve kaspar at imagineauto, i think that i shouldnt be worriying as much as i am. i think that the trouble with this board is that there are too many people that THINK they know what they are talking about when, perhaps they don't. I don't mean that in a nasty way-i dont wish to offend anyone-there are plenty of VRY knowledgeable and helpful people here, but if you take EVERYONES advice you will never get anywhere. take some advice from people who have done this lots of times and then stop taking advice!
Im going to stop rambling on now!

[Walt Fricke]

Andy

You are certainly right - if you try to take everyone's advice you'll go nuts. Your engine will probably be nice and dry.

If it leaks unacceptably, guess what: now that this business is not quite so mysterious and worrisome, you can pull it out, pull it apart, and reseal. No, you would dread that. But since you now know everything else is OK, new where needed, and clean, all the time you spent laboriously cleaning things, measuring things, agonizing about what to replace and what to keep, and so on, is in the past, and about all you might really need are new little O rings for the case through bolts, which are always a bit shreaded).

For what it is worth, for the dozen or so rebuilds I have done (all on my own motors) I've used the Loctite orange goo and it's always worked fine for me. I've had leaks aplenty, but not from the areas sealed with anaerobic sealants. One virtue of the orange stuff is that you really do not have to clean it off before resealing. It appears that it acts as its own solvent. Of course you have to know it is what was there - as in you applied it yourself - so with a motor new to you cleaning makes plenty of sense. This cuts out a step that can be time consuming.

The suggestion that the #8 O ring is misdesigned for sealing sounds like it could well be true. When compressed they flatten out a bit on their sealing sides, but do not fill their chamber - they don't seal on the fore and aft sides. I could see oil under pressure forcing its way past a nice compliant O ring.

I typically just reuse (contrary to all advice) the oil system sealing rings. They are captured in place and substantially compressed, and compressing forces them to fill out all the space available to them. Never had a problem (though only the oil cooler seals would announce a leak). On the other hand, the #8 O rings have always looked fine on disassembly, and I've reused those as well. However, these are engines with a known history (when I last rebuilt them).

The "SC" #8 O ring is a bit thicker, so just in case I've been using those.

I apply (as do at least a few others) a bead of case sealant around the thin outermost rib of the #8. On disassembly I usually find a little of this in the O ring groove, but always on the outside of the ring. I can't see how this would hurt anything.

No doubt with good sealing all around this bearing everything will work fine pretty much no matter what, but I am leery about sealant on the inside (toward the center of the engine) side of the bearing. I suppose it may not matter, but I'd expect some sealant to be squeezed out into the large cutout where the oil enters the bearing. Being anaerobic, it won't harden (at least not for a while and application of a fair amount of heat). If the oil washes it out and thins it, and it follows the oil through the crank and the bearings, then it should pose no more of a problem than the excess sealant which squeezes to the inside of the case at the mating surface. But that at least has to go through the pump and filter before it gets to close tolerance bearings.

In the photo one can see the drain groove which connects the sealing O ring groove back to the crankcase space. At first this bearing did not have this groove. I suppose that allowed oil that got into O ring groove to build up pressure and leak past the ring (or so Porsche engineers may have thought). So the bearing got the groove, and an Upfixin author suggested that owners of older engines cut such a groove in their #8 bearings (no one replaces this bearing in a routine rebuild as it doesn't seem to wear). Anyway, I'd not want to prevent this slot from doing its job (though perhaps if you seal the whole bearing it will have no job to do).

Those are my slightly contrarian thoughts about the risks and procedures I am willing to take and use on my own engines, which so far have worked.

Walt Fricke

(cleaning some heads he bought which look like one bank was sealed with gasket cement or the like at some point during a one sided top end job)

[adomakin]

wise words walt

[HKZ Bob]

Andy do you have addtional pictures of your sealing project.

robert.wartanian@web.de

Thanks Bob

[Henry Schmidt]

After reading through this thread, I have to point out one very important issue.
The o-ring and bleed system as designed for the #8 main bearing is flawed. It counts on the fact that the case where the o-ring seals is not distorted.
Distortion on the magnesium case is well documented. What is not well documented is that we have measured the case at the #8 main bearing to be .015" out of round on aluminum cases as well. There is no way an o-ring can be expected to seal in an out of round area. We have used oversized o-rings with scattered results.
This area can be align bored to .025 and bearings are available. The bearing is very expensive and only available through the factory..
Next, most machine shops do not align bore #8 because the tools for align boring quite often index in the #8 bearing. There are a few machine shops that offer a deck and return to stock align bore that will make sealing the #8 bearing without sealant much more successful.
After resisting gluing the bearing for as long as possible we researched the issue and made the most appropriate choice for success if no align bore is required.
Glue the entire #8 saddle and sleep well at night. There is no down side observed from this technique in 8 years and over 120 engines.

[HKZ Bob]

Henry you use ThreeBond 1211 on the 8 Brearing.

What amount on ThreeBond do u use.


Picture 1


Picture 2


Picture 3

Regards bob
Thanks

[Henry Schmidt]

Originally posted by HKZ Bob
Henry you use ThreeBond 1211 on the 8 Brearing.

What amount on ThreeBond do u use.

Picture 3

Regards bob
Thanks

Half the amount shown in this picture. A very this coat on the saddle only. Finger tip applicator is my preference.
There is no need to put any on the # 8 bearing itself.

[Eagledriver]

I haven't tried Henry's way so I won't comment on it but it here are some other ideas.

I had a leak on one engine that I built in this spot. I think my leak came from using silicon grease on the o-ring. The grease got into the case seam next to the o-ring and displaced some of the anerobic sealant. Shorty after using the engine I found the leak around the number 8 bearing. It wasn't bad so I lived with it but I was not happy about it. The next engine I built I used a dry o-ring and made sure the sealant got all the way to the edge of the case in that seam. The engine is dry as a bone after 1 year.

You have to be careful to watch the o-ring as you close the case to see that it doesn't get pinched in the case seam. One of Performace Products "Tech tips" tell you to use the bigger 3 liter o-ring on the 2.7 cases. This is a bad idea as the o-ring will certainly get pinched in the case seam. I had to pull apart my 2.7 case after trying to use the 3.0 o-ring.

-Andy