okay, case sealer again

[john walker's workshop]

you're in denial.

[350HP930]

Originally posted by john walker's workshop
you're in denial.

Or perhaps you are by blaming past assembly failures on an anaerobic sealant instead of other possible causes.

[stevepaa]

Originally posted by addictionMS
Is there a reason Dow 730 is not on your list of sealants?

Jim

No reason. I just started with 574, because of historical recommendations, and then because of some thread information, I looked up alternatives. My local mechanic switched from 574 to 518, the red stuff. I decided to look at 573 also. So from the specs 518 cures somewhat faster than 574, need to be nearly done in 30 minutes instead of 45. And it has about twice the tensile strength, shear is same. The real difference is the resistance to oil in that it get stronger with age.

573 is a very slow curing material, you'll have 6 hours to assemble, but you will then probably need to leave it sit for a couple of days before proceeding. Its shear strength is very poor

I made my choice for resistance to oil. There is really no test of shear or tensile strenght that I can see in the life of this motor. Well, maybe in the web joint where there is oil in the top passage, and so 518 gets better with age.

Thought about others, like Yamaha or Suzuki motorcycle sealers, but I'll try something already used by someone I know on this first try.

On my 912 some 15 years ago, I used Wurth Flachen-dichtung orange and that car does not leak a drop. Could not locate any more so I will try 518.

[ChrisBennet]

Originally posted by stevepaa
Thought about others, like Yamaha or Suzuki motorcycle sealers, but I'll try something already used by someone I know on this first try.

On my 912 some 15 years ago, I used Wurth Flachen-dichtung orange and that car does not leak a drop. Could not locate any more so I will try 518.

I think Andial & Porsche Motor Sports use yamabond (3Bond 1104).

I've used the orange Wurth flange sealer. It's the equivelent of 574 - probably the same thing repackaged.

-Chris

[stevepaa]

Originally posted by Rob 930
Hey Steve,

Drifting a bit from your original inquiry...

I've been wondering why your aluminum case looks all nice and shiny (like aluminum should) while mine (78 3.3) looks flat gray and oxidized, both inside and out, like it's made of magnesium.

My case is a 1992 C2 964, so it may just be the age

[stevepaa]

Other little tidbits. Talked to mechanic at Porsche dealer. He puts his sealer on the left case w/o studs. They also have been replacing the oil o-rings on through bolts as a matter of practice whenever they do a valve job.

My fasteners are still at the cad plater, so it looks like next week for assembly

[cstreit]

You know I've always been quite wary of the recommendation to tighten the perimeter bolts first.

In my mind you want to tighten the case through bolts first, to make sure that the case is really "centered" around the crank, then do the perimeters later. I realize that with a perfect case this should't make a difference, but I suspect that few of these older alum. cases are perfect.


Grey RTV silicone? scary business in my mind. Anything that hardens inside the case is bound to cause a catostrophic failure at some point.

[ChrisBennet]

Originally posted by cstreit
You know I've always been quite wary of the recommendation to tighten the perimeter bolts first.

In my mind you want to tighten the case through bolts first, to make sure that the case is really "centered" around the crank, then do the perimeters later. I realize that with a perfect case this should't make a difference, but I suspect that few of these older alum. cases are perfect.

That was my thinking also but a couple of leaking motors and talking to Steve Weiner changed my mind. Reading Greg Brown's article confirmed it - perimeter bolts first.

Originally posted by cstreit
Grey RTV silicone? scary business in my mind. Anything that hardens inside the case is bound to cause a catostrophic failure at some point.

That s**t scares me too but people don't seem to have a problem using Dow Corning 730 - a room tempurature vulcanizing silicone (RTV).
-Chris

[cstreit]

Chris,

I suspect that I'm being overly paranoid with the bolts. The 911 engine case is still pretty stiff so tightening the perimeter bolts probably tightens down on the crank bearings pretty good to begin with.

The RTV though, man, I just feel like you're tempting fate there... However I guess since the oil from the case is filtered first, any loose RTV could probably be ground up by the oil pump a bit and caught in the filter.

I suppose untill I have to tear one down because of a case leak I'm going to stick to the anerobics.

[stevepaa]

The 964 manual proscribes tightening the thru bolts first and in a typical expanding star pattern, then do the case perimeter without specifying any pattern.
I am inclined to do it that way. Thru bolts then perimeter. But I will probably do the perimeter in an expanding star pattern also.

[Rob 930]

There's a prominent Porsche engine builder in this area who uses a gray silicone sealant with great success on his engines (which currently include multiple 935s, 911s, and a 906 motor). That product is Permatex Ultra Grey 599BR. It says "Sensor safe RTV Silicone Gasket Maker." I don't know any more about it, but I thought I'd throw out another brand that has been used with success.

[john walker's workshop]

perimeter first if you use 574 or you could end up with the stuff setting up before you get to it. when the perimeter halves meet, it's essentially oxygen deprived, and the setup begins.

[stevepaa]

John, so perimeter first if one does not apply to the webs does make sense. Do you see any reason to apply to the webs? I think I'll get out my straight edge and see how flat the perimeter is to the webs

[stevepaa]

Flatness results. With my starret straight edge, the rh case is flat from one side to the other and across the mains, except above bearings 5 and 4 on the top perimeter where I can get .002 inch shim underneath. The lf case is flat everywhere.

[john walker's workshop]

you're not scared of 574 yet? even a bit leary?

[stevepaa]

I plan to use 518, the red stuff. very lightly on perimeter.

[cstreit]

JW, I am now...

[john walker's workshop]

a post above claims 518 cures faster than 574.....

[adomakin]

Łuck it. lets all just use chewing gum. it'll be fine. trust me.


Andy

[stevepaa]

andy, i love your "would like a big member" priceless