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fancytown
 
Join Date: Aug 2002
Location: DEE-troit
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Thru-Case Bolt O-Rings...am I OK???

Well today I reached a milestone in my engine re-build. I sealed up the case, and it went great...axcept for one part. During my "beat the clock" so the Loctite doesn't seal, I had removed some of the case thru bolts because the o-ring wasn't fully seated. It appeared as if some of them may have been pinched due to not having them fully seated, and then torquing the fasteners. If one of these was pinched or "shaved" a bit, will I have leaks?? What is the pressure in this gallery? I used a pretty good amount of RTV per Wayne's book. I know if a ring is cut, the chance of sealing is slim and none. Can the RTV seal on its own?

I was considering removing a thru bolt, one at a time, replacing the o-rings carefully, and then re-torquing. Will this compromise the case joint? I'm really happy with the way the case went together, so I don't want to split it again because the Loctite was applied very well. I just think the thru bolt o-rings might be compromised.

Any comments are welcome!
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Old 10-19-2003, 07:04 PM
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dtw dtw is offline
GAFB
 
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Read up on my experiences with this procedure here...

Engine building notes and gratuitous pics

If you decide to buy new o-rings and replace the current ones, be warned that you have hours of cleaning ahead of you. Getting the silicon completely and carefully out of the through-bolt bores requires bore brushes, compressed air, and patience. With all respect to Wayne's guidance on this, I will not be using the silicone ever again.
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Old 10-19-2003, 09:46 PM
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fancytown
 
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THanks for the advice all. With the silicone relatively "fresh" it shouldn't be too hard to remove. We'll see...
It's still better than splitting cleaning, and re-sealing the case. Oh yeah, and better than a leaky engine too.
Are these passages for the piston squirters??
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Old 10-20-2003, 03:23 AM
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Wayne,
I'm curious, who were your sources for the o-ring sealing trick?
-Chris
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Old 10-20-2003, 05:19 AM
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dtw dtw is offline
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Jay,
These passages supply the main bearings and the piston squirters. Getting a bit of silicone in a main bearing feed would be a Very Bad Thing.

I also thought that these would be easy to clean out, given that less than a week passed from installation to removal. The clean magnesium provided an excellent surface for the silicone to bond to - it was really time consuming to get rid of. And remember, you have to remove every bit of silicone from each through-bolt, nut, and washer.

When cleaning out the through-bolt bores, I removed one through-bolt at a time. Using a wire-bristle bore brush, I carefully scrubbed out one side of the through-bolt bore. From the opposite side, I blew out the hole with compressed air. In this way, no loose silicone was ever blown past a squirter or main bearing oil takeoff, risking a particle become lodged in the takeoff. I then repeated the procedure from the other side. Using a light glaze of fresh motor oil on new o-rings, I reinstalled the through bolt and torqued it before removing the next bolt.

There are two nuts with o-rings and washers in the chain case area that don't use bolts, but instead have studs. I didn't remove the siliconed o-rings on these. I was not confident in my ability to safely and completely clean these passages and studs while the case was assembled. Fortunately, these were two o-rings that showed no evidence of damage or improper seating. If they had shown any evidence of failed installation, I would no doubt have split the case again to clean them out. (Would not have made for a happer camper AT ALL).

Hope this helps, sorry if I'm being master of the obvious.
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Old 10-20-2003, 09:19 AM
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fancytown
 
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Thanks for the details Dave. I have no problem taking as much time as needed to clean this area up. It will take much longer, and be much more expensive to fix the engine due to a starved bearing.

By the way, as yourself, I'm using 2.2T pistons, but without any other mods. I bought my '72T in non-running condition, so I don't have any point of reference, but I'm anxious to see the performance of it. Actually, I've only driven a 996, so my point of reference is highly skewed. Unfortunately, I won't really drive it until spring due to crappy Chicago winters. Good luck with the rebuild...it sounds like you're almost there.
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Old 10-20-2003, 02:21 PM
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It seems to me that maybe you should assemble the case without O-rings and then install the O-rings and sealant one at a time when you have a bit of time.
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Old 10-21-2003, 07:20 AM
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My personal favorite are the viton rings. The are tougher than the POS blue ones. The blues shear far too easy. The viton is more resilient. You have to bit a bit more careful putting the rings on the case bolts, but other than that, piece of cake. AND you don't have to add some silly RTV to mask a poor seal ring design/material. I don't know if Pelican has these rings, but I know EBS does. They are pennies a piece more expensive than the blues and worth every cent.
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Old 10-21-2003, 02:12 PM
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Quote:
Originally posted by PBH
It seems to me that maybe you should assemble the case without O-rings and then install the O-rings and sealant one at a time when you have a bit of time.
Although you *could* logically glean this from my previous statement, I wouldn't recommend it. You really want to have the 574 set, and not be disturbed by anything, or risk oil leaks. That said, under controlled circumstances, you could probably remove each bolt one at a time and retorque without a problem, but I wouldn't recommend it unless you absolutely had to...

-Wayne
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Old 10-21-2003, 05:40 PM
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The silicone sealant around these bolts is not necessarily required (and I don't think Wayne implied that it was). My case is an '82 and I didn't use ANY silicone on it, to date, no leaks...

I did however lubricate the o-rings with assembly lube to reduce the chance for pinching and had a partner hold the base washer while I torqued the nut so it wouldn't spin and pinch the o-ring...
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Last edited by cstreit; 06-22-2004 at 07:09 AM..
Old 10-22-2003, 07:52 AM
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Slumlord
 
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Chris: I would agree, especially if you have just had the case spot faced, but I think 'the book' says you 'should' do it.
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Old 10-22-2003, 07:55 AM
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Personally, I think using silicone sealer (the type that hardens) on the O-rings is a "hack". It actually defeats the way an O-ring is supposed to work. If someone has leaks in that area I would look at prepping the holes better before I'd resort to sealant.
During assembly, I have a cutoff dixie cup of 30 weight oil that I use for lubing things with my finger (piston rings, Raceware rod nuts, etc). I put the case O-rings in that cup so they are well lubed before installing.
-Chris
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Old 10-22-2003, 08:24 AM
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I did not have my case "faced" and even "facing" a case rarely includes the o-ring area for the through-bolts.

No silicone, old case, no leaks...


...but then I'm the kind of guy that will tear something apart 4 times and re-do it to re-seal before using any unnecessary sealant...
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Last edited by cstreit; 10-23-2003 at 06:55 AM..
Old 10-22-2003, 07:50 PM
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Slumlord
 
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I only mentioned facing because it is recommended in the book and I just did mine.
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Old 10-23-2003, 06:52 AM
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Quote:
My personal favorite are the viton rings. The are tougher than the POS blue ones. The blues shear far too easy. The viton is more resilient.
Thanks for the tip Dave. My first impression of the blue O-rings is that they weren't as compliant as the original O-rings that were on the motor when I disassembled it.

Just to re-iterate my feelings on the O-ring RTV silicon problem is that the O-rings are designed to be squished so that they can conform to a pre-set given area. Too big an O-ring or to small an O-ring creates a volume fill problem. Adding silicon to the O-ring creates the same problem as using too big of seal and the extra volume has to go somewhere. Unfortunently, due to the O-rings compliancy it oozes along with the silicon.

O-rings designed properly shouldn't need any additional help.

Distributors come to mind.

I had a Trooper once that broke it's distributor O-ring. The original O-ring was discontinued. I tried all kinds of O-rings to no avail. If the O-ring was a little too small it would obviously leak. Too large and the O-ring would distort and leak. I eventually had to change distributors.

Bottomline we all drive cars, with distributors sealed by O-rings without additional sealants, that don't leak.
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Old 10-25-2003, 02:00 AM
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Quote:
Originally posted by Bobboloo
Bottomline we all drive cars, with distributors sealed by O-rings without additional sealants, that don't leak.
Yes, but I bet that the leak in your distributor was very easy to get to and fix, unlike the through-bolt holes.

-Wayne
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Old 10-25-2003, 12:23 PM
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Quote:
Originally posted by cstreit
I did not have my case "faced" and even "facing" a case rarely includes the o-ring area for the through-bolts.
Not meant to be preachy, but the reason why it's rarely done is because the cases are rarely sent to really good machine shops. I'm of course talking about mag cases now. Take a look at the through-bolt hole on page 51 of the Engine Rebuild book, and you will see where the metal has been perforated and deformed by the forces of engine operation combined with the through-bolt. This hole would need to be spot-faced in order to seat properly.

-Wayne
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Old 10-25-2003, 12:26 PM
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fancytown
 
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I feel like this is a different sort of synthetic oil vs. dino oil, so I'll throw a bit more fuel on the fire.

While viton would be a more durable o-ring than silicone, silicone will swell up some when exposed to oil. Thinking about this more, silicone would liekly seal better as it "grows". Taken nothing was pinched or cut. Not that this is too much of an issue with Porsche owners, but Viton has really bad cold weather sealing properties. It just gets too hard when the mercury drops below freezing temps.
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Old 10-25-2003, 03:08 PM
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