Your opinion wanted. Green bolt through viton o-rings with rtv

[HKZ Bob]

Dear all, & rebuilder, your opinion wanted.

I am rebuilding a 2.7 motor and following Wayen Book. Instead of lubricating the o-rings I decided a described in W-book to used green viton o-rings @ bolt through screws with rtv.

In the dry phase of threebond I saw some little egde green o-ring rest squezzing out of the washer.





Who is running his engine with the an equal issue at the bolt thru bolds.
Do you have a leak. I just have to again mentined that I have RTV Loctide 5900 smeared around the o-ring and tighten them with 35Nm.

Let me know what you think.
Best regards Bob

P.S
Maybe Wayne can give some advice.

[HKZ Bob]

Here some more pictures.





Thank you for your help.

Bob

[cgarr]

Were the O-rings installed during the initial assembly and torque down? If so there may be a problem? (May), Or did you torque it all down without the seals then remove one bolt at a time and add the rings?

[lucittm]

You have about a ton of pressure under that beveled washer. I would offer that the o-ring is doing its job. It's just that you can see a small part of it due to a tiny defect in the case.

Mark

[HKZ Bob]

Hello I was installing the o-rings together with the final assembly of the case.

bob

[Henry Schmidt]

We only use green o-rings Dow 55 o-ring lubricant on the case through bolts. If the case is properly prepared this is the best method.
Generally any RTV is a mistake on a 911 engine. Experts may disagree.

[HKZ Bob]

Henry you like these pictures which I have seen before. This is a butchers rebuild attempt,

but let's focus on my question.

bob

[304065]

Bob,

The trouble is that the through-bolt passages are also oil passages. Any RTV which squeezes out into a bead under the bolt head is free to break off and travel through the oil system. Because these passages are right next to the main bearing saddles, it is not recommended to use RTV sealant there. That said, Wayne has done it as have probably hundreds of others, so I would not run the risk of messing up the bearing clearances by removing the through-bolts to clean out the RTV.

On my engine I used the Viton seals with Dow Corning 111 lubricant. This allows the o-rings to move around inside the chamfered washer and seat against the bolt shank and head. Your picture almost looks like the Viton ring has been squeezed out between the case and the washer! That is not good, I would definitely untorque that one to verify that the washer has not distorted into an oval shape.

[Henry Schmidt]

Originally Posted by HKZ Bob

Henry you like these pictures which I have seen before. This is a butchers rebuild attempt,

but let's focus on my question.

bob

Bob
you call this builder a butcher and Wanye called him an adviser.

Just ignore the pictures and read the text. I believe it answers your question.
If your question is "Will it leak?" Who knows ? If you don't do it correctly you roll the dice and takes your chances.

"We only use green o-rings Dow 55 o-ring lubricant on the case through bolts. If the case is properly prepared this is the best method.
Generally any RTV is a mistake on a 911 engine. Experts may disagree."

[Daniel Cooper]

I have had my motor back out several times based on through bolt leaks. The key to getting a good seal on a 2.7 mag case is to bevel the cases. The holes in the case go out of round as the case halves shuffle, and often little edges build up--at least they did on mine. Ollies recommended that I use a countersinker tool in a tap holder and clean up the bevels. Wayne's book only mentioned beveling the holes in passing. Before I did this the o-ring squeezed out of the washer as in your photo. After it seated nicely and I have no leaking from the through bolts now. A pain in the ass requiring substantial disassembly but that is what cured my problem. Good luck !

[Bob Goding]

Just my 2-cents worth ,from my own experience with one 7R engine.
It seems that the thruebolts go in from the -101 or distributor side with the dome nuts on the -102 side.
on my engine,there is/was no chamfer on the holes in the -101 side and a small chamfer on the other,nut side. This seemed to be opposite to what one would expect.
The only place for the o-ring to go is into the chamfer in the washer--ideally half in the washer and half in the case---if the space in there is insufficient the seal must squash out. [or squeeze into the case hole.] in my case these thru-bolt holes measured 10.6 mm dia which is quite loose on a 10mm bolt.--Important then to make sure the washer is the correct way round.
Obvious enough on the bolt head end---but the other end is a bit of a design disaster as the o-ring sits on the thru-bolt thread--hardly an ideal surface for a seal !I guess thats the reason for a dome nut !
I have an own design fix, but I have to prove it first.
If the case halves have been machined and the thrubolt surfaces have been spot-faced this removes a portion of whatever chamfer might have been there originally.
Amazing that hundreds of engines have been reassembled succesfully, but obviously there have been some "Leakers"!
I believe that the later engines[3.2/3.6] have a redesign in this area.
Comments welcome.

[WERK I]

Originally Posted by HKZ Bob

Let me know what you think.
Best regards Bob

P.S
Maybe Wayne can give some advice.

I think it's going to leak and RTV should be avoided anywhere in rebuilding these engines.

When torquing the thru-bolts, the non-chamfered side of the case bolt/nut can not move one iota. If it moves, it will either tear the o-ring or do what your pic illustrates. I don't know why Porsche didn't chamfere both both halves of the case, maybe they had a jig that kept the thru-bolts stationary while torquing.

[930LDR]

So I just completed my case sealing job today (for the second time). Used the viton green rings and dow corning 55 on them. Managed to pinch a few of them (similary showing as above but without the RTV). I'm guessing I shouldn't have much to worry about in removing and replacing the o-rings (one at a time) on the offending thru bolts once everything has cured?

[4sd911]

A little bit of O ring squeezing out isn't a problem just make sure the washers are seated against the case, see this tread.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/533517-problem-case-bolts-viton-o-rings.html

[lindy 911]

Originally Posted by 4sd911

A little bit of O ring squeezing out isn't a problem just make sure the washers are seated against the case, see this tread.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/533517-problem-case-bolts-viton-o-rings.html

I respectfully disagree; If the o-ring does not seat against the bolt shank, washer bevel and case face it will leak. I used the "Waynes book" method the first time around and it leaked from several locations. I held the bolt tight against the case when tightening for absolute no movement and they still squeezed the o-ring out. Even with the RTV oil was everywhere.

Listen to Henry. I used green Viton rings and silicone grease supplied by and recommended by Henry and all the through bolts are bone dry. No case chamfer, no silicone RTV and no blue o-rings.

[Walt Fricke]

Well, everyone's mileage varies, but I have had a bit of blue O ring squish out under the odd washer. While hardly encouraging, these have not leaked on me. Of course, I could have been lucky and these were never on the main bearing oil passages.

Counterholding carefully to prevent the bolt head side from moving is important no matter what, but you can't prevent the washer from moving on the nut end. At least I can't.

So it is your roll of the dice.

[BURN-BROS]

There are only a few thru bolt hole that see pressurized oil. The rest do not technically need them.

Henry's instructions work very well. Be sure to use a liberal amount of silicone paste when installing!

[opticalfuel]

Hi Guys,
reading up here on the issue related to through bolts. I have a generous amount of drips coming now from the through bolts on the bottom bolts close to the #1 Cylinder. It was pretty dry for a while, and now have a pretty decent leak. I think what it must have been is that I rev'd the engine to about 6500 + a few times when it was pretty full of oil, 11qrts or so... and it then began to leak more. I must have popped one or two of the o rings... As far as I know they are the original bolts, and orings. (a 1980 SC 3.0 liter - case never split - only rebuilt case outward) All the bearings that were possible to replace we did. There was no indication that the seals were going to be an issue.

Like I said the motor was bone dry till we replaced the oil last time, then after a vigorous run it dripped. It's only coming from that one location (near the # 1 cylinder)

While annoying, the dripping does not seem to indicate a worse problem, except now I must wonder just how much oil is being lost during a drive. I guess it depends on how much I romp on the engine. It only expels about a cap full of oil or less. It's just not clear how much comes out when I am driving it. It seems to be significant, because it spatters on the back of the car, and makes the muffler wet.

I am tempted to take the engine out and take it all apart and re-do all the bolts and o-rings, but then I think about the fact that it runs so well. If I screw something up while trying to fix an 'annoying' oil leak... am I just trading a small problem for a SUPER expensive one. If I don't build it back perfectly - the oil leak will seem pretty preferable to a blown engine. Also... if I have the engine that far apart - WHERE do I stop? It could literally turn into a major rebuild, instead of a simple oil leak fix.

Know all that... Can anyone say with any certainty how much oil is likely passing through those o-rings? Its probably impossible to say.

More importantly ... if it's true that the engine case is basically 'factory' are the o-rings that are in there now the 'green' o-rings or are they the original 'black' ones? or something else?

Feel free to chime in.

My instinct is to keep adding oil, driving it like normal, and wait till a more pressing reason to dig into a rebuild. (maybe decades from now?) - at least until the rings need re-doing.

[DaveA]

When I assemble an engine, my friend Dennis Parker and I work together, and hold the beveled washers with vise grips to ensure that washer does not spin and tear the O-ring. Of course, we make sure that the holes are beveled before we start. Works well.

R/Dave

[fred cook]

prefer without. Trick seems to be to not let the washers turn while tightening!