too cold to rebuild
 

I am starting to reassemble my case and wondering if it is too cold to seal the engine. Using loctite 571 and RTV gasket, and curl-t. Temps outside are in the 30s and garage is in the 40s.

I don't know of any limitations on the temps but I bet the containers have that information or it could be found on the manufacturer's websites. Curil T is non hardening so it should be ok as long as it is not too thick to work with.

-Andy

The temperature is the least of your issues.

Loctite 571 Thead Sealant and Silicone RTV? (The Curil-T is OK)

My personal recommendations: (this has been heavily debated--do a search)
-Threebond 1211 on #8 bearing
-Threebond 1104 on case perimeter, and between heads and cam housings
-Curil T on cylinder base, flywheel seal, #8 nose seal
-Loctite 574 on through-bolt main bearing webs
-Loctite 518 on gasket surfaces (chain housings)

That said, as long as the sealant is not too thick to spread thinly, it's OK

Please do not touch a 911 engine with silicone RTV

I thought the preference was to use the RTV on the through bolts to help seal with the o-ring and beveled washer.

That's what the book says.. but I will have to respectfully disagree with that method.

My personal recommendation is that, if the through bolt holes are in good shape, and not ovaled or gouged, then the o-rings can do their job.

For those, I use Dow Corning 55 or 111 lubricant, to prevent the o-ring "pinching", then I torque to the spec. (26 lb.-ft ?) No issues and then the guy that takes apart the motor next will not have to deal with rock-hard silicone on there. Also, the silicone RTV can break off and jam in the oil passages and destroy the motor.

FWIW.

It can't hurt to use a very light coat of the same stuff you use to seal the case on the green o-rings for the through bolts.... I imagine the cold temps will only lengthen the curing time...

JB

Using sealant on o-rings CAN hurt. O-rings are designed to move a bit, and seal the surface irregularities in the holes that metal parts can't. If you goop them with sealants that harden, it prevents the o-rings from being effective. RTV, 574 and even the case sealant I mentioned, Threebond 1104/1194, are hardening/semi-hardening sealants, and you do NOT want those sealants on o-rings. If the hardening RTV gets cracked, the whole glob of RTV is still stuck on your case like a MFer and you still have an oil leak.

The issue with leaking from the through-bolt O-rings is when you use the standard blue rubber o-rings and the o-ring gets pinched between the washer and the flat surface, not nicely pushed into the edges of the hole like they are supposed to be. The factory used motor oil, I recommend Dow 55 O-Ring lubricant, to allow the o-rings to comfortably slide to where they need to be (the hole) before you torque the through-bolts.

I have researched all different kinds of sealants and looked into others recommendations. There are multiple ways to seal an engine correctly, but not all sealants are created the same. There are all different kinds of bases (silicone, polymeric, acrylic, ester, etc.) that have all sorts of properties: drying/semi-drying/non-drying, fast/slow set times, anaerobic/aerobic, thick/thin, high/low shear strength, lubricants, for large gaps, small gaps, metal joints, gasket replacement, o-rings, rubber seals, viton seals...there are thousands of different types of sealant. You can't just substitute one for another because they are both "sealant".

I'm just trying to offer useful advice because I've been there and tried a bunch of them. I've never had a leak on any engine I have built. But, go seal your through-bolts with RTV for all I care.

A little bit of sealant on the o-rings is fine, you're over-thinking it. These are known leak areas, particularly if the surface is not flycut beforehand. There really is no downside to it.

-Wayne