As I was breaking in my new OS GT22 I noticed that the bolts securing the muffler were loosening after a brief cool down. Tried star or split lock washers however negative solution to this problem. Has anyone experienced this and what else can I try to resolve it ? Thanks...

I would purchase some Permatex Ultra copper high temp sealer and some blue loctite thread locker The red is for high temps but if you need to remove the bolts it will be very difficult . I would then remove the muffler and gasket , throw the gasket away . Clean the bolts and threads with alcohol to remove oils. Coat the muffler and cylinder exhaust port surfaces with a very light coat of Ultra copper . Apply thread locker to the bolts and install muffler and tighten bolts. You eliminate the gasket because it compresses and allows movement , removing it will help to improve the clamping power of the bolts. The thread locker prevents loosening from vibration

Great advise from CK. However I have used red loctite with good success. When I need to remove the bolts I heat them up with a 25 watt soldering iron. That being said most of the time when your muffler is coming loose it's a good indicator that the engine is getting too hot.

The muffler came with ordinary flat washers. Should I use a lock washer or will the blue thread lock be sufficient ?

Use a lock washer between the bolt head and a flat. Try the blue loctite but only after the bolts and threaded holes have been cleaned well with acetone. Get the engine off the bench and flying. Gassers don't need bench running and doing so is increasing its running temp and contributing to your issue.

See if you can buy a bolt for the muffler that has a big head on it. Drill a hole thru each bolt head, After tightening them down run a wire thru the holes in both bolt heads and twist them together... This way they are tied to each other and can't loosen up.

Welcome to the forum. I always make sure the machined surfaces are very flat, and take a new fine toothed file to make sure it is flat. just a couple swipes with your thumb pushing down. I don't use a gasket. If it still comes loose, then tightening it again while it is warm may help. Heavy mufflers are a problem sometimes. The other tips are good, and worth a try too. You don't want to lose your muffler in the air. Safety wiring the bolts, and even an extra one on the back of the muffler is a good idea too. especially on a boat or combat plane.

Anytime I've had a muffler come loose is when I didn't tighten the bolts securely enough. I would think with a split lock washer and some thread locking agent, tightened really good (don't break the head off), you should be good.

Ok food has the answer it's called safety wire.
But if you don't want to safety wire then heat up the engine through running it. Tighten the bolts while hot.

I have 2 of these, loose the gasket, use silicone, and drill the bolts for tie wires that will solve the problem

Thank you gents for all your in put to this issue. Prior to drilling the bolt heads I will try the Permatex
High Temp Copper gasket maker and blue thread locker suggestion from CK.
Stand by for a follow up report !

Whatever you do, don't flip the prop right after putting on the sealer before it's had a good 24 hours to cure. You could blow it out of the muffler/engine joint and lose the seal.


carl

OK Carl, Thanks for your tip...... I mounted the engine onto my "Clipped Wing Cub's firewall, however, cannot fly at least until April (field conditions) I'm looking forward to the first flight, landing and then checking if those d**n muffler bolts budged !!!! So,,, what to do in the mean time,,,, OK, time to start building the Waco

Teflon pipe thread tape on the bolt threads works very well. I've found that Loctite is not good to use on aluminum threads with steel bolts, threads are damaged easily if removed very often

Fairmont MINN......I used to live about 5 miles north of there....how's the weather? I sure do NOT miss the weather/flying season from November until May!!!

Jerry Festa

Yes Jerry, Our flying season is too short. However we take advantage of our winter season to build. It's -1C today and glorious sunshine .

There is always indoor flying. Maybe I can go tonight. Saturday one of the neighbors kids was walking on the beach in bare feet. This is Canada!!!

New bolts stretch a little. All new fasteners do when tension is put on them. There are two ways for a bolted attachment to get loose. The first is by the bolt unscrewing, and the second is by the bolt stretching. A bolt holding on your muffler is a lot like a rubber band holding something together. It's the stretched tension that does the work. When you tighten the bolt, you probably will noticed that after it gets snug you'll find the torque steadily increase until a certain point, then it increases sharply. That sharp increase is the limit of stretch the bolt can handle before being damaged. So most of us have enough experience to not overtighten our bolts. After that first run, the heat cycle and the tension that's been on the bolt stretch it a little, which does the same thing as loosening it. BTW, the aluminum you are tightening it against can also deform under tension, adding to the problem. With a new engine, you'll probably need to retighten all of the bolts after a little while, maybe a couple of times. The bolts will settle in soon though, and when they do you will be able to go all year without doing anything to them. To verify all of this, put a dot of white paint on the side of the bolt head and also on the aluminum it's bolted into. That will let you see if the bolt has actually unscrewed when it gets loose or if the problem is caused by stretching or deformation of the aluminum.