Anyone else like cleaning your expensive top of the line gas engine as much as me when the fricken muffler to block connection leaks???...... What's the deal on the best way to connect your mufflers to prevent any leaks? I've heard everything under the sun: gasket only, no gasket and use Permatex, use Permatex and the gasket, use the red Permatex, use the black Permatex, use the copper Permatex, lions, tigers and dude enough already... What say you gents?

I guess I wouldn't know. I don't use the expensive, top of the line gas engines.

I just use the gasket that comes with the engine or muffler, if the muffler is a separate purchase. I also make sure to use locktite on the muffler bolts. This helps keep the bolts tight.

I haven't had to clean my engines when I do it this way.

I use NO gasket, red RTV, and #277 Locktite on the bolts with 24 hours for everything to setup (cure) before starting the engine. Never have any leaks there.

First things first. For whatever reason, engine vibrations, is causing the bolts to loosen. Reduce the vibration. Balance prop; balance spinner; etc.

Les

Thanks for the info guys! One more quick question on the red RTV, the instructions say lay your bead, tighten the bolts hand tight, wait 45 minutes to an hour then give them a 1/4 to 1/2 turn more. I tried that once and the muffler bolts loosened up, even with Loctite. How do you guys use the Permatex? Thanks again!

Personally, i put a very thin film of permatex (Red or Copper) on the muffler side and then make sure that i carefully mate the surfaces together squarely and the muffler doesn't slide around. In most cases you can hold the muffler off about 1/4" while you thread the bolts, then tighten the bolts 1 turn at a time.

I also put a smear of the permatex on the bolt threads instead of Loc Tite

This has always worked great for me.

On all my engines, I lay a piece of Teflon tape (plumber's tape) across the mating surface, pop a couple of small holes at the bolt locations, and a small slit in the exhaust opening.When the engine fires, it will break free the remaining tape barrier in the exhaust stream, leaving a Teflon gasket at the mating surfaces.

I like the really wide tape, making it easier to hold in it place as I bolt the muffler on; however, if you have only the narrow stuff and need to cover a larger area, just lay down a couple of pieces, overlapped - the exhaust area itself will then be partially open already and will blow fully open upon starting the engine.

I don't bother with Loctite on the bolts, but I do make sure that they are really honked down tight, and I try to remember to check them every decade or so. As I have experienced a couple of muffler losses in the distant past, and have had bolts loosen in more modern times (NOT due to my gasketting technique), I usually do one more thing - especially on my OS engines, as those things seem to be prone to divorcing their muffler. I use some safety wire wrapped around the muffler body and extension, then around the cylinder head once. Taht way, if the thing does loosen, I don't lose it.

I have been dong this for over 20 years, it works for me. "Your mileage may vary..."

I do this on all of engines - never had a leak or a lost muffler. Don't over think this - red rtv works great.

You're right Cobra, don't size the nail up, just hit the damn thing! I've had better luck myself with the red rtv and loctite actually, but wanted to hear what you guys had to say. One more quick question, do you guys lay the bead then crank it down, or do you lay the bead, hand tighten then go 1/4 to a 1/2 turn more about an hour later like the directions state or do you lay it, wait then crank it down? I'm trying to get to that "Set it and Forget it" Graceland!

Arrow,

Here's what I've been doing sucessfully for more years than I care to count. I do not use the gasket, but I do put a thin coat of RTV on the manifold and tighten up immediately. After 12 hrs (or overnight) I start the engine and bring it up to operting temp, shut it down and immediately re-torque the securing bolts. That little bit of bolt/screw strech the temp produces is taken up when tighten after running the engine. The type of RTV is not too important, as all of them are of a high enough heat tolerance that you don't have to purchase the high-temp stuff. (I'm sure I'll have those who disagree chimming in) If you ever get the chance try to melt some clear, or blue RTV that has been cured, try to. Trust me, it'll take a blow torch and then some to melt it. Point being = if you have any type of RTV, it'll work fine.

Kaos, now that's what I'm talking about! Thanks for the tip, even my little pea brain can calculate that and makes perfect physics sense too, much appreciated!

I agree with Kaos on the type of RTV. I've used clear, black, Ultra Copper, etc, etc, etc. All work fine. (I do use the RED if available as it is slightly higher temp though not by much) I do NOT do the semi tighten thing. I tighten them fully on the first shot. If it's a pitts style then I make absolutely sure to run a support at the opposite end to control vibration which works to loosen or possibly crack the muffler.

Jezmo, great point on the support! Can you find these standard or are they a custom jobby? The set up in question is a DA85 with a pitts.

This is what has worked quite effectively on a few thousand gas engines used everyday.

No gasket, a thin layer, very thin since it's used as a sealant not an adhesive, of Permatex Ultracopper on the muffler flange surface, and Red Locktite on clean threads. End of story.

T.O.M,
Any of those thousands of airplanes got supports on the pitts muffs? If so, are they a standard type of purchase or custom?

If you can't hold bolts in it, stud out the holes in the block with threaded rod or long bolts that have been cut for their threads. Put heavy compression springs behind the nuts and washers.

The trick is don't try to keep the muffler tight. All you want to do is keep the muffler sealed. The right springs will do that for you. Hot two strokers, dirt bike and snowmobile exhausts been doing it for years, you'll even see it in production cars. You can't hold a steel screw in an aluminum block tight for very long if theres extreme heat and vibration. It has to do with coefficients of expansion and contraction of the two materials. Just heating and cooling it without even running it will loosen it, sort of speak

Hunt down the shortest, heaviest compression springs you can find and make studs for the block. You will save the threads in your block also before its past the point of it still having good threads to work with you having to keep putting a wrench to it. Thats only good for so long before things start to strip out and the frequency of having to tighten it goes up.

The pic i put up is a bolt-through motor with tapped header. I put RC Car clutch springs behind the screw heads instead of dealing with keeping screws tight in the header. The bolt threads go through the header, and a jam nut run down to keep it. An ape could not seperate the seal, yet no screws are holding it tight.

+ 1

For what it's worth I don't run a gasket at all on my car or my trainer, and neither of them leak anything significant from the exhaust port. I just crank the header bolts down as tight as I feel I can without stripping them and I use some loctite to keep them that way.

Well, it looks like your back to lions, tigers, and bears, oh my! I use the gray permatex gasket maker because it is oil and gas resistant and was made for exhausts and carbs. A thin coating on both surfaces and then RED loctite, the blue will not hold up to heat.