New DLE35-RA, should Iuse Loctite and if so, which type? Anyone else with this engine using the gasket or not? Thanks!

Use red Loctite, no gasket, and let it dry overnight before you use it. I like to use a thin layer of hi-temp silicone in place of the gasket. Do not re-torque the bolts.

AV8TOR

Permatex Ultra Copper works great if used without gasket, also a bit on the bolt threads works great too.

Permatex high tempature thread sealant, comes in a little tube like locktight

Plus 1 on the above comments. No issues after adopting these methods. Mufflers stay on for years.

My DLE30 has gasket....blue loctite.......split lock with flat washer. Never had a loose muffler yet using gasket with this method,G26 DLE30 DLE55. It should be noted I also have never flown a plane without balancing the prop also.....sometimes other little things help in keeping things tight.

Neither red or blue Locktite will survive the temperature the muffler screws are subject to.
You need a silicone based glue like mentioned in the above posts.

For going on 15 years now I have been using Lock tite 272. The screws and threaded holes are cleaned with acetone before installation. I also take and block the muffler flange first. I have had very few issues with mufflers working loose. Usually I have to hit the screws with a 140 watt soldering iron to get them loose. It appers that there are several products that will work as there are several different methods mentioned in this thread. IMO the key to keeping the muffler from working loose is to carefully balance your prop and spinner and more importantly do not run your engine too hot. In all cases the cylinder and muffler are different alloys and the screws are steel, all different expansion rates thrown in with most thread locking compounds don't work past 300 degrees well.

I have been using red loctite labelled as "high temperature." No issues.

+1

And when I do remove a muffler that has had red Loctite on the bolts, they go "craaack" when they come loose and are a bit stiff turning out, indicating the Loctite was indeed holding.

AV8TOR

+1 to your comments. Likewise, when using the high temp red Loctite, the bolts come out with a nice "craaack" as you indicated. The only muffer I ever had a problem with was the original Syssa muffler and I felt its problem was a design problem that has since been rectified.

Check the specs. No locktite is rated for the temperature expected of muffler bolts.

From the Loctite website:


<h1 style="">Loctite 272 High Temperature, High Strength Red Threadlocker</h1><div class="longText">

</p>

Top Pick Loctite&reg; 272&trade; High Temperature, High Strength Red Threadlocker withstands temperatures to 450&deg;F. Provides a fast cure on most surfaces, including "as received" fasteners. Recommended for bolts up to 1 1/2" (36 mm) in diameter. Heat and hand tools are required for disassembly.</p></div>Dirtybird, just how hot do you run your engines?

I really don't care about the specs. I do know that I get the results I want with the materials I have been using. When the bolts resist being removed after being in place a year or so, the results speak for themselves.

For years I used regular Loctite red on glo engine muffler retaining bolts with the same results. I still use that material on my helis as the high temp loctite seems too strong for the purpose and I fear the smaller bolts might twist off when attempting to remove them.

One thing that I rarely hear mentioned and that I do on a regular basis ..... I use muffler retaining bolts that engage as many threads in the cylinders as possible. Sometimes these may be up to a 1/4" or so longer than those supplied with the muffler / engine. I feel this gives much better support for the muffler. Some bolts as supplied may only engage 3 or 4 threads which is simply not enough to retain the muffler properly. Another point, some cylinders require that a bottoming tap be used to insure the cylinder threads are tapped as far as possible. Of course, bin any crummy hardware and only use quality, graded bolts.

Engineering requirements require bolt depth to be equal to the width of the bolt. Any more is just a waste of the bolt.
The temperature an engine runs at is quite a bit less than what the muffler bolts are subject to. They are in the path of the exhaust. 450 degrees is not enough unless they are out of the muffler. Most gasoline engines have their bolts passing thru the the muffler.
Silicon glues have a much higher temperature rating and they have the advantage of you can remove them when you want to.

I'll be sure to remember that the next time I see a steel bolt cleanly pull the threads out of aluminum.

Lets see, given your formula, a typical 5mm muffler bolt would have just over 4 threads holding into the aluminum cylinder. Is that really enough? I have rarely seen any engine or muffler supplied with bolts that had that little thread engagement and when I did thought it was an error on the vendor's part.

I'll leave it at that.

If the cylinder where the muffler bolts go is reaching 450 degrees F., you have more problems than your muffler coming loose. The cylinder head itself, which is the hottest part, should never approach 450..... Yes, the exhaust gas temp itself may reach as high as 1300 to 1400 degrees on a lean run (more like 1000 to 1100 degrees normally), but the cylinder itself never reaches that; at least not and stays serviceable....

AV8TOR

Red Loctite has never worked well for me either. It's good to see that some people are having goog results with it, but I never have. As soon as I started using red Permatex, my problems went away.

I have that engine, I used the gasket.  It also had a great number of flat and lock washers that need to be installed in a certain order, that is what I did.

Red Permatex is a silicon glue. Its mostly made for gasket formation.

The head dont reach that temp but the bolt does.

Dirty bird you are talking out of a book and that is a USA book to boot not metric when you say the thread depth should equal the bolt diameter is not the rule for metric bolts due to the finer more shallow threads. I have seen many pull tests over the years and that theory of the bolt diameter is nothing but reading material on smaller fasteners no mater what thread they have.
As far as a muffler locktite go's I use the blue and so far have had good luck with it, for years I never used anything until I had one come loose on me.
You claim the red does not have the heat range needed for a muffler but yet it sometimes takes a torch to get it loose. I think the 425 degree rating is well under what it really is.

Dirtybird is correct. Maximum bolt holding strength is obtained when the bolt diameter = depth of thread. Measure the thickness of a 5mm nut and see what you get.

But that formula would apply to steel bolts and thread. I would think when using softer metals it would change. You would need more thread engagement.

Most times when a thread is stripped, it is because the bolt has been over tightened.

I have an engineering book that says 3 times the diameter of the bolt !

Regular red is 350
High Temp is 450
Silicone is 450

The "high temp" will work only on nitro two strokes. On a four stroke nitro I melted alumiweld stuff that is 730 deg. I doubt any of the above will work on Gas either - but no experience.

dont use the RED you will never get the muff back off,the blue comes back off,I use star lock washers,you can get them with ID and OD locking,I use ID that means the solid part is on the outside of the washer,any hardware or part stores carry them.I never put any kind of goop on my engines.just a thought.