Tom F

This is a long post, so I'll skip to my main question first. However, if you've studied the problem of sealing up 911 engine cases, I'd appreciate your reading the balance of this message, and giving me your opinion.

My main question is what is the truly best way to reseal the 911 engine case? I heard from a Loctite engineer that their domestic product no. 518 is the best for aluminum cases, but that RTV is the way to go for magnesium cases and for racing applications. I've used 574 with success in the past, but read on, and you'll see why I have a question now.

Now for my long winded explanation and request for advice. I am trying to decide whether to disassemble a partially assembled motor because of what I perceive as a "Loctite build up" problem around the crankcase flange, which looks to me like it may cause leakage, or worse, problems down the road. I am not keen on redoing 8 hrs. of work (I was all the way to timing the cams when I noticed the gap in the case!), but I don't want a leaky motor, either.

I am in the middle of reassembling an early sand cast aluminum case 2.0 liter (a very early '67, which still has the adjustable endplay intermediate shaft. This was a factory engine, i.e., I was the first to disassemble it - it still had the original sealant around the case flange, and this was very thin stuff, more like the old fashioned "Permatex Form a Gasket." It was thin enough that it was clear that the case halves were touching in places.

I put the engine case together with Loctite 574. (Isprayed Primer N activator on the case half where I did not spread the 574. I have found that the primer improves the curing of the 574.) I disassembled, and then reassembled the case a second time, because the first time I put it together I couldn't see a bead of the orange goo peaking out around the entire perimeter of the case, as I have other times I've assembled case halves. When I put it together the second time, I added a little more 574. Now, it looks to me like the case halves aren't touching in the flange area. At a couple of corners around the flange that aren't filled with 574, I can get a 0.2 or a 0.4 mm feeler gauge in! (The corners are at the rear top, in the fan pedestal, and in the front top, above the flywheel.) On the other hand, I am confident that I have the flange area thoroughly filled with the 574, and that the stuff will set because I used the primer, but having all that soft Loctite working its way loose in the flange looks to me like it's going to cause trouble down the road.

For now, I'm planning on disassembling this case yet a third time. However, if you've seen this, maybe you can help spare me a third teardown of this case. Has anyone ever seen this problem of Loctite "build up," and can they tell me whether this is something that I can live with?

Thanks for reading through this "book"!!

Tom Frisardi
tfrisardi@msn.com

john walkers workshop

i used to use 574 for years with fairly decent results. no primer though. the last time i used it was several years ago on a 930 rebuild. there was oil leakage right away between the case and the nose bearing. total teardown to find, just as you describe, a thick loctite crust that kept the cases from squeezing the nose bearing o ring enough. it was either a bad batch or old, but i've used DIRKO since with even better results. 574 is anaerobic,(sp?), meaning it sets up when deprived of oxygen. once the case halves meet, you shouldn't waste a lot of time torqueing things up. perhaps yours started to set up, then you split the case and added more, instead of cleaning it all off and starting again.

kwdotis

Hello. I just finished rebuilding my 911 motor using loctite 574 and I put a thin film of Curil T behind the O-ring on the nose bearing. Case sealed up beautifully but 2 days after start up, I sprung a pretty severe oil leak between the case and the nose bearing. I had never seen this before and I was so mad that I yanked the motor back out and took it apart to see what was going on. I should have never used Curil T behind the O-ring because the O-ring was not free in the groove and did not seem to find center of the nose bearing; the o ring was not doing it's job. I was just curious how you fixed your leak and if you used any type of sealant on your nose bearing.
Thanks.

Ed Hughes

You'll find an excellent thread on the Pelican rebuild forum on this topic. I used 4 different sealants last time. I think I used three bond on the nose bearing seal to the case.

TT Oversteer

My understanding about Loctite 574 is that applying it over cured 574 should dissolve the old sealant. In fact, I have heard of some using new 574 to remove the old. I sealed my case halves with Threebond 1104 and the nose bearing with Threebond 1211. Do read the Pelican "complete engine sealant" thread:

http://forums.pelicanparts.com/911-e...nt-thread.html

I sealed my rebuild exactly as described there and so far not a drop of oil anywhere.