I heard that there is some kind of auto muffler patch material that will lock muffler bolts, it is supposed to be very high temp and does not lose it's strength like Loctite does at high temps, anyone know what it is?

I know the epoxy your talking about. I bought some, but haven't used it. It's a 2-part expoy in a tube. Squish and mix, then squeeze it out. The package says that it gets stronger with heat.

For muffler bolts that you want to put in and make permanent, I like to use #640 loctite. It's called Sleeve and Bearing retainer. It's used to put steel cylinder sleeves in automotive engines and also used on babbot bearings and rod bolts.

When you put it on the muffler bolts of a gas or glow engine--it works extremely well. It won't come out. You need to make sure everything is spotless and clean before using it. Any grease or oil will hurt the bonding qualities.

You can get it loosened up if you take a propane torch to the bolts and heat them beyond 500F.

I just did it yesterday. I used this stuff to put some 8/32 studs in a glow engine. Then I use nylon lock nuts to hol the muffler on. I got stupid with the wrench and tightened one of them up enough to snap the all thread stud off. Took it home and hit it with a mapp gas torch a couple times. Keep the torch 8-10" away from the engine and just let it heat up slow. Tok about 5 minutes of slow and even heating around the all thread studd to loosen the loctite. Then it came right out.

Under normal flying and running--this stuff is permanent. I've never had a bolt or stud come out of an engine or muffler. Been using it for 5yrs.

You just have to make sure everything is clean. Run a tap in your threads and clean out any old loctite. Use acetone or some other strong solvent--along with a pipe cleaner--to get down in the threads and clean them up really good.

Use a dremel with a wire brush attachment to scuff the black paint off the threads of a socket head cap screw. Shiny, clean, metal--to--metal connections and this loctite will not come loose while flying.

Hope this helps.

I have been using high temperature RTV for the last 4 years and I haven't had a muffler come loose since. You can purchase this at any auto supply store. I used to use the red but last year I changed to the black that GM uses for exhaust gaskets. Don't use a gasket between the engine or muffler or the muffler will become loose as soon as the gasket is blown. Use the RTV on the threads and all mating surfaces. Your muffler screws will remain tight and you won't need a torch to remove your muffler if you try this method.