Journal Web Sealing

[alphie]

Getting very close to closing up my 3.0 case. Doing lots of research here on Pelican about sealants, procedures, etc.

This is a first time for me (a 911 engine) and I'm taking it VERY slowly. I plan on using Threebond for the case permiter sealing.

My question is about the journal web sealing (by the through-bolt holes). I know Henry and Wayne use Loctite 574 in this area yet others, Bruce and John Walker (I think), use nothing as the factory did.

I imagine the logic behind using the sealant here is to seal the through bolts as that is a high pressure area. Oil to the oil squirters is supplied through those holes. After spending hours unclogging my oil squirters I was wondering what effect loctite 574 might have if it got in from the web journals after the case is torqued down.

I am also wondering how effective 574 can be in this area. If you look at a main webs you'll see that there is only 2.5 mm of sealing area on the sides of the bolt hole. Yes the rest of the web is quite large but for the loctite to succeed in its purpose it must seal an area as small as 2.5 mm.

Any thoughts? As I mentioned I am a strict amatuer in this area...

-Rob

[cstreit]

Well in theory the 574 shouldn't cure in areas outside of those seams. It is an aerobic sealer meaning it will only cure in between metal surfaces and not sitting in open areas inside the case.

I don't use it on the main bearing webs as this seals pretty damn well around the oil channels otherwise you'd have crank problems.

[Eagledriver]

I see no reason to use sealant there and some possible problems if you do. Why take the chance.

-Andy

[davidppp]

There is a good reason IMHO.

Namely shuffle..

I confess to having built one vw motor withe the webs glued together for this purpose.

It seemed to work too...

kind regards
David

[sand_man]

I've got just over 500 miles on my 3.4L Turbo rebuild. I DID NOT use any sealant in this area. So far, no leaks. IMHO, sealant in this area is another opportunity to screw something up. My machinist, Neil Harvey of Performance Developments (who was in the race engine development department with Andial (pre-PMNA) days) also advised against it.

[Henry Schmidt]

The case through bolt holes also acts as a oil passage to supply oil to the main bearings. Because the main webs are inside the engine there is no way of telling how much oil (oil pressure) is lost from this area if it is not glued. It is also possible that the 574 would add structural rigidity to the case.
Necessary ? maybe not Harmful ? If it is please tell me how. 574 in small quantities will not block squirters.
Main bearing oil pressure? priceless.

If you have even seen 3 lb oil pressure in your engine when hot, you know what I'm talking about.

[cstreit]

Originally posted by Henry Schmidt
The case through bolt holes also acts as a oil passage to supply oil to the main bearings. Because the main webs are inside the engine there is no way of telling how much oil (oil pressure) is lost from this area if it is not glued. It is also possible that the 574 would at structural rigidity to the case.
Necessary ? maybe not Harmful ? If it is please tell me how. 574 in small quantities will not block squirters.
Main bearing oil pressure? priceless.

If you have even seen 3 lb oil pressure in your engine when hot, you know what I'm talking about.

I agree I don't think it would hurt anything... And a bit of 574 certainly won't hurt... Otherwise the squeez-out that gets in at your case seams would wreak havoc.

3 psi hot? Jack up car, insert new engine. YUCK.

[Eagledriver]

I bought an SC engine in pieces that had 3 cam spraybar holes blocked by excess loctite 574. That is the danger. The engine had 3 cam lobes worn out and 3 worn out rockers due to this problem. Admitadly this engine probably had way too much sealant used but I don't think it would take much to cause problems. As for sealing the webs I doubt you could measure a difference in oil pressure considering how tightly the webs are bolted together.

-Andy

[Eagledriver]

The "squeez out" that Chris mentions isn't inside the oil passages of the engine. At worst it will go through the scavenge side and into the filter. The excess that gets into the through bolt holes can go anywhere down stream in the oil system.

-Andy

[alphie]

Andy, that is my fear as well. If I don't apply it properly the squeezeout will go into the through-bolt holes and into the system prior to scavenging.

I know from cleaning the oil squirters that it doesn't take much to get them clogged.

As far as providing structural rigidity, I have to say I'm skeptical of that. If for some reason the force in the engine is great enough to move the webs I would bet that loctite isn't going to help.

[Henry Schmidt]

Andy , you are correct. If way too much 574 is applied to the main webs you will have excess squeeze and that can't be good.
That is where the art comes in.
Building Porsche engines with that last little bit is what makes the difference between a DIY engine build and a craftsman.

Knowing what is too much of anything, is the art.

Too much compression, the much cam, too much carburetor, too much header and too much glue. It all part of the craft.

Too often "more is better" but after 30+ years and 400+ engines, knowing how much is appropriate, is what you pay for.

As for the main webs moving, they can and do move. A small coating of glue between two tightly clamped pieces of metal will do more than you might imagine. Thousands of ft/lb of difference.

Lets reverse the thinking. If we lubricated two tightly clamped pieces of metal [let's say with mds / molly] would they be more likely to move or less ? Go ahead and say it, you know, come on. Of course, it's more likely to move. If a thin coat of lubricant will help it move why wouldn't a thin coat of glue be more likely to prevent that movement?

Did you know the the main bearings also move? The next time you take an engine apart look at the back of the bearing.
Racing mechanics of old used to put lanolin on the backs of bearings to prevent fretting.
This allowed the bearing to move more freely without welding itself to the main cap. How could a small amount of lanolin make a difference? It only mattered to the artisan and the finish line.
How long ago you ask ? I read an engine development from Porsche race division from 1987 that used that exact method to help resolve a crank issue they were having in a 600hp 2.5 engine.
Does Porsche manual tell you to put lanolin on the backs of main bearings ? I haven't seen that.
I guess there are some things that the racing division doesn't share.
I on the other hand will and do share everything I've learned with anyone who wants it.

* Just one added thought. If the main webs moving is not a problem why did Porsche make the case through bolts stronger in the late 70's ? *

[alphie]

I would estimate that most of us on this board are Porsche DIYers and not craftsman. We all appreciate expert advise from Henry, John, Wayne and others provide to this forum. I agree with Henry, a craftsman is seperate from a DIYer and as such you get what you pay for.

However, for us diyer's I think we need to be careful since we don't have the experience the others have. Many of us will build less than 5 engines in our lifetime. I can just see someone slapping loctite on everything and end up causing way more trouble than what they are trying to solve. I count myself in that group.

For me I have to decipher what the experts do (and in this example, some highly regarded experts do not put loctite on the webs - another example being the rod bolts), versus what I am capable of doing.

Regarding the web mains moving, I don't think anyone said they couldn't or wouldn't move. If they didn't then shuffle pinning would not be done. If I don't use loctite in this area I risk the webs moving more than if they didn't have loctite (how much is debatable) and high pressure oil blowing past the main webs. Applying loctite myself I risk getting squeeze-out in the through-bolt holes and into the squirters, cam bars, etc...

[Henry Schmidt]

Little weed hopper, don't be scared.

Squeeze out would be minimal or zero if caution is used. If there is truly a concern, pump up the oil pressure and let the engine sit for a few minutes and the 574 will cure in place.
The oil will remove the oxygen in the tube causing the anaerobic compound to cure. I've seen 574 cure in the bottom of an oil pan and found it hard to remove.

[Eagledriver]

I had no idea that main bolts were changed in the 70's. Just one of many things I still have to learn about these engines. Thanks for sharing this and everything else.

-Andy

[cstreit]

My feeling is though, any oil inside the case is going to go through the filter before hitting the engine pressure side, so any cured "squeeze out" (good point on the sump oil removing O2 henry) would be filtered first.

I'm just wondering about the sheer load on those bearing webs and whether or not the 574 could withstand it.

[Henry Schmidt]

Although I could find no data on 574 that pertains to aluminum, the lap shear strength ISO 4587: steel is 1,230 psi.
Imagine the increased shear strength if the two pieces of metal are clamped together at say 26 ft/lb.
By itself 574 would add very little shear strength but in combination with torque the shear strength should go up exponentially.

I repeat that we use 574 to seal the oil passage but the increase in rigidity offered by the addition shear strength of the 574 is a bonus.

I wonder if we should just go on beating this thing to death?

[davidppp]

Another anecdote from VW days:

I have more than once been instructed to rebuild a motor with a worn case:

The problem is normal in any VW engine revved over 4000 regularly...the middle main bearing saddle gets oval..and the flywheel saddle too..and the flywheel one also beats out the thrust faces.

I have had very good luck using 574 in this sistaution behind the bearing shells..oilpressure is manintained and the engines lived..

Nor a recommendation, just another data point.

The fit and finish of shells and their housings is a much-neglected area for fast engines..

I have heard unattributable stroies about fast motorcyle engines and F1 engines using locktite products behind the bearings..

I am one day going to try this with a worn 911 case..

Kind regards
David