Really great to see this thread continually updated with all of the data points and experiences. At some point (hopefully a long way out), I'm sure I'll be pulling the 993 engine to have the valve guides done (top end) and I'm sure to refer back to this thread for guidance...

What size tubes of threebond 1184 (1104,1194) and threebond 1215 (1211) are needed. I'm seeing a few different sizes listed on the various sites.
thanks.

3.5 oz tube should be plenty with some left over. Get a couple tubes and have some extra around in case you need or want to redo something.

Does anyone know the difference beetween Threebond 1104 and 1104 Neo?
I can't seem to find much info regarding Threebond products.

Edit: After asking Three Bond about this, they say that 1104 Neo is the same product, made in Malaysia. 1184 is the US replacement for 1104.

NEW LIST (I've lost the ability to Edit Post #1 since it is from 2008...)

Outer Case Halves: Threebond 1104 (now 1184)

Bearing Saddle Surfaces: Loctite 574

#8 Bearing (balancer end) O-Ring: Threebond 1211 (now 1215)

Case Thru Bolts: Dow Corning 111 on Green Viton O-Rings

Flywheel Seal: DRY

Balancer Seal: DRY

Intermediate Shaft Cover to Case: ThreeBond 1211 (now 1215)

Oil Breather Cover to Case: ThreeBond 1211 (now 1215)

Cylinders to Case: Curil K-2 or ThreeBond 1211 (now 1215)

Cam Towers to Cylinder Heads: Threebond 1104 (now 1184)

Cam Chain Housings to Case: Threebond 1104 (now 1184)

Cam Chain Housings to Cam Towers: Threebond 1104 (now 1184)

Cam Chain Housing Cover to Cam Chain Housing: Threebond 1104 (now 1184)

Gaskets: Thin coat of Loctite 574

Thanks a lot folks, I really appreciate the feedback!

EDIT: Most Popular solutions for sealing added to each item above to include superseded items.

:cool:

As a professional Porsche engine builder with 30 years experience and over 400 total builts, I can attest to the consistency of this process.
Although many builders find the LocTite on the main bearing saddles to be unnecessary, we find that it adds a definite shear strength at the case joint. This shear strength helps prevent case shuffle. (Not as well as shuffle pins but better than no adhesive at all.
The Dow O-ring lubricant (55 or 111) does exactly what it was/is designed to do. It lubricates the o-ring preventing tears during installation and after the engine/ sealing surface reaches operating temperature, there is a chemical reaction that swells the o-ring filling any void around the sealing surfaces.
The o-ring during operation is constantly in compression, never tension.

Improve the breed. Advance. Choose a ring lube that doesn't degrade your seals.

There is ZERO evidence that Dow 55 O-ring lubricant "degrades" o-rings in any meaningful way. Change does not equate to "degrade" and in fact, I would argue from experience that "seal swell" is a positive innovation in this application.
In fact, the military calls out Dow 55 for use on an incredible number of weapons systems both vintage and modern day.

I have seen no documented cases of o-ring failure do to Dow 55.

In the interest of improvement, if anyone has documented evidence that Dow 55 has caused an o-ring failure, I would be interested in that evidence.

Same old dance Henry. Welcome back...

http://i458.photobucket.com/albums/q...ps13839b78.jpg

Graphs and charts are very impressive. The Global Warming community can attest to that (flame suit on). I am not taking sides on this topic that refuses to go away, but before anyone has the final word, I, for one, would like to see the test criteria and environment that produced the results above.

(No tone implied here) So which one to use? None? What's your recommendation?

Dupont Krytox. More spendy but there's a reason.

The use of the diagram I've shared above is for educational purposes only.

The original diagram before mark-up for education is from Dow Corning Corporation and is copyrighted.

Form No. 10-773B-01 AGP4616
Here's a link to the PDF document:

http://www.calo.co.kr/pdf/download.php?id=yg_sg_dc-55M

The test conditions as specified in the title of the document are under ASTM D412, which is updated periodically:

ASTM D412 - 06a(2013) Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension

With most things in the physical world, there are compromises.
Engine building is no different.
We give up compression for driveability and we sacrifice weight for cost. We sacrifice horse power for torque.
The question is always "what is the trade off?"
In the graph above (from Dow research BTW.) you see only one criteria.
During the development of Dow 55, the engineers set the criteria on multiple levels.
They wanted to enhance the sealing properties as well as enhancing the life of an given o-ring while providing lubricant for installation.
To these ends, they decided (correctly I believe) to enhance the sealing properties by expanding the o-ring after installation.
They were also interested in enhancing crush resistance of a given o-ring over time and heat cycles.
They accomplish these goal by slightly changing the o-ring with a propitiatory chemical formula.
This chemical change in no way degrades the o-ring in a way that causes it to deteriorate. Much to the contrary, we have found over years that the o-rings seem more elastic after long periods with the Dow55 than without.

To my knowledge, no other lubricant offers these properties.

If we were, let's say building a slingshot we would probably choose a different treatment for the elastic material but I guess if I were building a sling shot I might solicit the advise of Dennis the Menace for his anecdotal expertise.

Henry, what would you describe the relationship between the o-ring and the threads on the through-bolt as? Do you compress a tomato with a knife?

After installation, the relationship between o-ring and threads is a non-issue. I have never seen a leaking case o-ring precipitated by cuts (your knife analogy) from case bolt threads. I have seen leaking precipitated by seal hardening and sealing surface degradation (mostly mag cases). Even with case degradation, we see good sealing with the Dow 55.

Truth be told, after the first couple of hours of engine life, you rarely see case o-rings leak no matter what lubricant is used. Most leaks are caused by poor installation techniques. We just like the insurance offered by using Dow 55.

Have you considered there are better options out there? This is what I believe I'm presenting to you and others with the alternative Dupont Krytox. I understand you love the DC55 and you're spinning the lost of strength as a positive now that you're aware of it... but there are options that don't cause that drop in strength. That's insurance Dow 55 doesn't offer.

Haven't we had this little discussion a few times? How about if you professionally agree to disagree rather than have a neurotic conversation and damage an otherwise very valuable thread.

Us mere mortals will pick one side or another and just go with it....personally I am a Dow guy but I only have two engineers in the family so my sample size is small...

Dennis

Indeed we have but it's important to consider the ramifications. If you use Henry's suggestion of DC55 without chamfering/beveling your case holes then you're effectively mixing gasoline with fire. It's a reckless suggestion to not include the machining/beveling requirement next to the grease due to the profound negative effects on the Viton. Not everyone plans on beveling their case halves when tackling the job and if they're shopping for the quick data point of which grease to use when assembling (purpose of this thread) then they could be making a BIG mistake. DC55, as accepted and proven countless times on this forum now, reduces tensile strength (which corresponds to tear resistance) of Viton by nearly half. Will his suggestion of DC55 work as long as you've beveled both halves? The answer is yes, for awhile although it will likely shred on the bolt thread. Henry's answer is also that you must bevel everything. Why play games though? There are alternative greases available that don't pose the same risk. Educated consumers can choose more wisely knowing this information.

Hesitate to jump in here, but +1 on Dennis' post. I guess there are points both ways here, but the value of this forum is shared experience - so we don't repeat, or manage to avoid mistakes.
Henry with 400 engine builds beats me by about 396. So I greatly value the contribution by guys like Henry who freely share their experience. Experience being the key word here.
Henry has something that works for him - time and time again. So it will probably work for others also. There may be other options/alternatives, and if others choose to go another path, so be it. But I don't think castigating someone for not ditching a tried system that works, for some other plausible option gets us very far.
I've seen very valued experts having their shared thoughts torn up on these boards before, and choose not to post. Easier to ignore the forum and get on with what pays the bills. Hopefully guys like Henry will continue to share with us, and if others have another view, post it. But if it works for 400 engine builds, surely we can accept it is a viable useful technique at least in this specific instance (and thanks for sharing it).
Alan

Alan - I hear you and many other members of the forum on that point. Henry wins the popularity contest hands down with his claims of business. I offer only facts for analytical minds and submit no resume for review as it only distracts from the topic of the moment. Those with the herd mentality may continue to drink their punch none the wiser but don't sandbag new, revealing information that those with brains and decision making power may find useful.

The main difference in this case, and the reason why I am so passionate about getting the information out, is the danger of a half opinion that Henry has shared. His suggestion of DC55 is contingent upon the case being beveled. That prerequisite is omitted (dangerously in my opinion) from the sealant list. If you're not beveling your case halves then DC55 is an absolutely terrible suggestion for the lube to use. I would further the recommendation against the DC55 due to the thread on the bolt.

We hear you, understand your point of view. Is there a way you can draw a line under this area of discussion as neither Henry nor you are likely to change your mind on this particular topic.

We, the great unwashed, want to ensure that neither of you get so ticked off with this particular brushfire that they cease to post, whereby we collectively lose the valued experience that us home mechanics need.

We have seen too many skilled people leave these groups because of the kind of argumentation you are engaged in....please stop on this particular detail, it is not helping.

Dennis

Amen!

Sure, we can draw a line under it. I'm not ticked off just insisting that the horse stands before the water to consider a drink before jumping over it and proceeding down the trail. Be rest assured that every time someone chimes in that DC55 "it's simply the best" for this application, that I'll be waiting with the asterisk to say "not so fast" and show people why they need to be careful with partial advice.

http://www.miller-stephenson.com/ass...8x270/Food.JPG

DuPont Krytox GPL 207 Grease, Pure PFPE / PTFE No Additives, 0.5 oz Tube: Amazon.com: Industrial & Scientific

http://www.krytox.com
http://www2.dupont.com/Lubricants/en_US/assets/downloads/elastomer_compatibility_profile_K20565_1.pdf

Google Dupont Krytox. $140 for 8 oz!!!! I think I'll take my chances with Dow 55

Edit - I was typing while Lapkritis put up the last post. I can live with $20.

What is the rationale behind using the silicone-based 1211 on the #8 saddle, rather than just using 1104 (rubber based) like the rest of the case perimeter?

Am I asking for trouble if I use 1104 here?

Whatever you use on the #8 saddle, apply it SUPER thin. The #8 is a precise fit in the case halves (it has to be, since it acts as a locating/alignment sleeve at the end of the case) and therefore it will squish out whatever excess it doesn't want in there.

The rationale for any sealant here is that it is a backup plan for o-ring leakage. I like to use the inert Dow 112 o-ring lube since it not only lubes the o-ring but it also protects it from oil contact that degrades the rubber.

So you just use the lube and no sealant?

Yep no sealant there since my engine gets taken apart way too often. For a long term leak free engine, I think the sealant around the #8 is a a really good idea. Just use it very sparingly. You don't want any squish getting into the oiling holes.

The reason for gluing the #8 main bearing is that the cases (more often than not) are no longer completely round. Over years of use, they tend to become oblong.
This part of the case is generally not align bored (although there are over-sized bearings) so correcting this ovality is somewhat problematic.
By gluing this bearing you overcoming this inconsistency. Will it seal without glue? usually. Is there any drawback to gluing this area? not that we have seen.
We use 1211 because it tends to be slightly more elastic to deal with the expansion difference in the early mag cases.

Have built over 25 engines using techniques and products like Henry suggests. Our engines don't leak. But, remember, no choice of sealants will overcome poor cleaning, inspection and preparation...

We use an "o-ring lube" we get from a local motorcycle shop on o-rings and have not had any issues. I am out and need to source some more... I don't know the properties of it, but I know it has worked well for us.

Cheers

I hate to prolong the argument and as a technical guy, that chart is showing tensile strength measurement. And it does show a loss. These o-rings under the case bolt washers are used in compression to make the seal as I understand it. If I'm wrong, please correct me.

We've beaten it to death. You're not compressing the ring against the bolt thread just as you are not compressing a tomato with the blade of a knife.

And there are other such edges in the joint especially if it is not chamfered/machined.

Since it doesn't seem to be covered in Wayne's book, how and when do you apply sealant to the cylinder base gaskets? I don't see how it would be possible to apply the sealant, get the heads and cam towers on, then torque the head studs all in 30 minutes (curing time for 1211)

FWIW, this is on my 3.2 with .5mm bare copper .5mm gaskets.

I only recommend 1211 in certain applications.
The best product we've found for cylinder bases with copper gaskets is Curil T. It never hardens so assembly time becomes a moot point.


As for the comment by our resident antagonist: We use Dow 55 on all case o-rings (chamfer or not) with exceptional, long term results.

Edit: we actually use Dow 55 on every o-ring during the air-cooled 911 engine assembly not just case through bolts. It works exceptionally well on oil return tubes, cam joint rings, RSR rocker shaft seals, cooler seals as well as all rotating surfaces within seal.

Hmm, take advice from a guy who builds engines for a living, whose name is on here plainly and on what he sells, or someone anonymous in name AND location? What to do.....??

I knew what I did on the two builds I have done, and I took Henry's advice.

Thanks, Henry.
Do you think one is likely to see a leak here if sealant is not used?

It's a toss up. The cylinders are constantly moving so there is a opportunity for leakage but there is no steadfast rule. Sometimes they leak and sometimes not. With sealant you improve your chances.
Most of this thread is about just that: not what is "right" or "wrong" but what can I do to improve my chances. What I offer is for just that purpose....best possible chance based on my experience.
Cheers

I'm just glad to see Henry posting his great advice again.
When I put my new top end on last April I would have used Curil T on them if I had some but I used blue hylomar I bought off ebay because I had a tube of it.

I think they're kinda similar because they both never dry and stay gooey and resist gas and oil. Lacquer thinner will desolve hylomar and I use a rag wet with it to wipe off any hylomar squeeze out after tightening things down.
Anyway, they havn't leaked or sweated any oil.

I used Hondabond 4 on the cam tower to head surface and it's not leaking either. Lacquer thinner on a rag cleans it up too.