Lock tite on pipe

[melderor]

When you mount the header and pipe to your engine do you use lock tite ? If so Red or Blue.

[DavidH]

Heat will soften loctite and is a method to release it, Really no reason to use loctite on bolts that are threaded into the engine.

David

[TheBum]

As someone pointed out in another thread, the differences in the coefficients of expansion between the aluminum pipe and steel bolt will help tighten the connection.

[Pinecone]

Heat will soften loctite and is a method to release it, Really no reason to use loctite on bolts that are threaded into the engine.

David

Funny, you use Loctite on full sized engines.

[DavidH]

Yep on some parts of full size engines there is loctite used. But the parts it is used on are not usually in a high heat area. Usually it is anti seize being used where studs screw into aluminum heads on full size engiens.The cylinder head and muffler mount are high heat areas on model engines. And those are the only bolts other than the four in the back plate also.

David

[Pinecone]

How hot?

I just got a Norvel Big Mig .15 and it uses O rings for the engine to muffler seal.

And the head temps are running only 100 - 110C on models.

[DavidH]

For Loctite 242 which is the general purpose blue that is widely used 85 deg Celsius is the max temp. Fastners with this loctite on them will loosen just by applying additional torque to them. Normally no heat is required to break them loose.

271, the red that is most commonly used in the hobby. Normally heat has to be applied to the fastener to soften the loctite to remove the fastener. About 250C is needed in the most stubborn cases. This is considered permanent type loctite.

There is some high temp loctite also, but the two above are the most common used in the hobby that is referred to as red or blue.
And when using loctite on aluminum, the threads need to be cleaned each time the fastener is taken out or installed. The loctite will cake up and strip the threads. Been there done that a few time.

David

[Pinecone]

Looking at the data sheet, 242 retains more than 50% of its strength at 100C. And 30% at 150C.

One could use 246 which keeps more than 50% of its strength up to about 275C.

So the answer is, normal Loctites don't really work well on muffler screws, but there are products that do.

[DavidH]

Yes there is definitely some loctite products that would hold the muffler screws in the engine. But better make sure every thing installed is like it needs to be and you don't need to remove the screws after it sets. The loctite that we normally use in the hobby is perfect for 2mm to about 6 mm fasteners. You start getting loctite that has more bonding strength and the fasteners are going to be more difficult to remove.
The original question was about the more common red and blue used in the hobby is what I thought. Most in this hobby are not going to hunt for a specific loctite, they mostly will just use 242 blue or 271 red. As I mentioned in a previous post. I have seen loctite cause the threads in aluminun to strip out. Unless the threads are cleaned each time before re installing a bolt or screw. Need to take a tap and clean the loctite residue out before reinstalling a bolt.

David

[Pinecone]

Actually the true answer to the original question is, you can, but you don't need to, and if you do, neither of those two. :)

And 242 is fine up to much larger fasteners. We use it on suspensions and engines for full scale cars all the time. Same with 271, but not so often. About the only place I use that is on oil pump drives and wheel studs.

One slight rant, we need to work on people getting out of using color, as there are many blue, red and green products, even from Loctite company. I have three types of green on my bench. Wicking grade for threaded fasteners, 290 for slip flit non-threaded assemblies, and 638 high strength for tight fitting assemblies (gret for pinions).