Case sealant on one side, right?

[75-911S]

I've read and re-read all the threads on case sealant and decided to follow John Walker's suggestion to use Dirko. I just want to make sure that I should only use it on one side of the case like Wayne does for Loctite 574, right?

Jack

[Henry Schmidt]

A very thin bead on one side should be enough.

I would add this. Dirko is a silicone based sealant, so if you apply too much it will form a bead on the inside of the case and with time that bead will break off and travel through the engine. It has been my experience that silicone sealant are the # one cause of piston squirter and rocker spray bar clogging. This clogging causes premature failure do to lack of proper oiling.

That is why we don't use silicone base sealant on internal engine parts.

Silicone sealant works cool on water pumps. Opps, that's right real 911s don't have water.

[code7rpd]

Henry,

What do you guys use as sealant - the Locktite product or the Dow Corning stuff?

[75-911S]

Wow Henry, I had not heard that about possible beading of the sealant inside the case.

Thanks for the heads up.

Jack

[Henry Schmidt]

We use three products to seal our cases.
ThreeBond 1211 on the # 8 main bearing.
ThreeBond 1104 on the case perimeter cam towers.
Loctite 574 on the main webs and miss gaskets.
Curil T on the cylinder base gaskets.

On the gaskets that are prone to leaking we use a very thin coat of 574. Very thin , like a glaze. There are some other tricks we use but I guess life should have some mystery.

Does this seem excessive? Well this works for us and allows us to offer a 2 year warranty that include oil leaks.

[bbh03]

Henry, what is the difference between 1104 and 1121? Also, what are miss gaskets? Am I missing something here?

[Henry Schmidt]

1104 is a semi-drying, high temp. synthetic rubber, liquid gasket used to join parts having large clearances.

1211 is a self curing, heat resistant, silicone sealant that becomes tack free in 30 min and fully cured in 72 hr.

This seems contradictory to my statement about silicone on the inside of engine but in this application there is no bead formed on the inside that can break off.

MISS= miscellaneous

[bavaria911]

Henry,
Sold!

When I very return to the States and get the 911 out of storage....the engine is yours to rebuild!
Leaks and engine rebuild "money back or repaired" w/i 2 years...you have my business.

Vr,
Bavaria 911

[bbh03]

Oh, misc! When you say misc, do you pretty much add the sealant to all engine gaskets, or only select onee, like cylinder base, etc? I'm assuming its a very thin layer in these cases.

[john walker's workshop]

if the sealant pieces did come loose and fall into the engine, how would they end up in the oil passages? oil and particulate matter gets scavanged out and gets run through the filter before it's used in the oil passages again. i think the problem is from people using it in the wrong places, like on the main webs, around the through bolt bores, or cooler and oil pump o-rings.

[Henry Schmidt]

Your observation is mostly correct.
On early cars not all oil is filtered all the time. When the engine is cold and making the most oil pressure the some of the oil by-passes the filter. I have seen amazingly large pieces of crap get past the screen on the scavenge side oil the pump. Once it by-passes the oil filter it's a straight shot into the pressure side of the oil pump and off to the bearings, squirters and cam spray bar.
Does it happen allot? no When it happens is it bad? yes

Worth the gamble? you choose

[Henry Schmidt]

Originally posted by bbh03
Oh, misc! When you say misc, do you pretty much add the sealant to all engine gaskets, or only select onee, like cylinder base, etc? I'm assuming its a very thin layer in these cases.

Just gaskets prone to leaking as we have experienced over the last 30 years of building 911 engine.

[philippeF]

"......We use three products to seal our cases.
ThreeBond 1211 on the # 8 main bearing.
ThreeBond 1104 on the case perimeter cam towers.
Loctite 574 on the main webs and miss gaskets.
Curil T on the cylinder base gaskets....."

Hello
1) need some help ...
May someone draw on a picture the exact location of the sealants as i unfortunately don't understand all the words : (main webs?)....

2) M. Schmidt
something seems strange to me : i've "locked" the two parts of my mag case to perform the bearing measurement :
it's around 62.005... that seems right
but ! what about the clearance with the case sealant ? is it so thin that we don't consider ? or is it going to be 62.010 or more ?

3) May you tell me the price for your "adjustable cold start device" for MFI ?

best consideration
Philippe from France.

[75-911S]

Man, this has really gotten involved. Am I to understand that some people use Dirko/574/518 around the case perimeter but don't put anything on the webs next to the main bearings?

Jack

[bbh03]

You must seal the main bearing webs. Those who are not aren't following the proper procedure and may have extra play in the bearings. Bad.

[Jeff Alton]

A while ago on a "case sealing" thread, Henry was kind enough to post a pic outlining where each of the sealents he recommends are placed.


Cheers

[john walker's workshop]

Originally posted by bbh03
You must seal the main bearing webs. Those who are not aren't following the proper procedure and may have extra play in the bearings. Bad.

bearing play from not using sealer on the webs? explain.

[philippeF]

catca> good news, i've not found it now, ....
anyone else ?
Philippe

[Henry Schmidt]

When properly installed, case sealant should add little or no additional clearance to case halves. It should not effect bearing clamp. The bearing is are under pressure when installed and the clamping pressure is important to proper bearing function. The amount of pressure placed on the bearing is a matter for debate but everyone should agree that there should be pressure and that the specific pressure should be not and is not affected by sealant in a properly designed and assembled engine.
A thick coat of 574 Loctite can and quite often will effect bearing clamp.

Historical note: During the development of the 944 GTR the engines designers of the time were having problems with the main bearings moving in the block during relatively short runs.
They had constructed a very stiff crank (a real piece of art) and a Nikasil lined block that was also very stiff so what was the problem? The designers were at a impasse as to how to remedy the problem (movement = wear, friction and failure). They basically had two directions to proceed. Higher clamping pressure or lubricate the bearing to prevent failure. They chose to put lanolin on the back side of the bearing to prevent damage when the bearing shuffled around in the saddle. For those who remember, the 944 GTRs were very fast but rarely finished any races.

[Walt Fricke]

One of the things in Wayne's book I hadn't seen before I read it was application of sealant to the main bearing webs. I am pretty sure that the factory manuals (which I have, but not at hand just now) do not specify doing this. Nor did Haynes (but one makes allowances there). I'm pig headed enough to cut corners or ignore Factory directions sometimes, but I like to think I do so knowing what the Factory recommends, so I don't think it is in the Manual.

So the thought of doing this never crossed my mind. If a little oil leaks out in the places where the through bolts carry oil, so what? It goes into the sump. And the chances of some Loctite or other sealant working its way into the bearing proper is increased. I'd been meaning to ask about that.

Now I see Henry Schmidt does this, too. Why?

All my race cases have been shuffle pinned to date, but I'm not planning to do it with my Carrera 3.0 case because it ought not to need it (and I see from the Forum that it may even be a bad idea). Does the sealant prevent the web faces from working on each other? Seal the oil passages? Something else?

Walt Fricke