icabod

My Feedback: (29)

I was wondering why you should not use a gasket on a gas engine muffler, but should use a thin film of high temp gasket seal instead? thanks

w8ye

My Feedback: (16)

Gaskets seem to burn out right away and cause other problems in the muffler attachment area

All Day Dan

My Feedback: (5)

Use the orange RTV, no gasket. Dan.

CK1

My Feedback: (60)

The gasket eventualy compresses which allows a reduction in clamping force ,the muffler then loosens and the gasket is etched away from vibration/friction between the 2 surfaces.
Use of a good" high " temp sealant (permatex bronze )instead of a gasket along with a good threadlocker on the muffler bolts will remedy the exhaust leakage and keep the muffler tight.

aussiesteve

One of the weirdest Radio interferences I ever experienced was caused by a leaking and slightly loose exhaust a few years ago on a 36MHz PPM radio.


On most of the engines and exhausts used in our hobby, Gasketed exhausts will usually come loose reasonably quickly. The use of High Temp flexible sealants such as High Temp Silicon compounds keeps the exhaust sealed and in place.


There are a couple of reasons.
MOST of the mufflers we use do not have a particularly flat surface on the sealing face. This means most of the high temp gasket materials are struggling to hold a good seal for long (if at all). Once that seal is compromised (even a little) then the rate of loss of seal is exponential from that time onwards.

MOST of the Cylinder exhaust flanges we use do not have a particularly flat surface on the sealing face. This means most of the high temp gasket materials are struggling to hold a good seal for long (if at all). Once that seal is compromised (even a little) then loss of seal is exponential from that time onwards.

MOST of the Mufflers we use are of a very lightweight construction which will distort with temperature changes.

Good flexible sealants such as Permatex Ultracopper will accept the discrepancies in the sealing faces and will tolerate some movement of the selaing faces from temperature changes.

If an engine had a machined exhaust flange face, a robust muffler with a machined face and a properly resilient gasket, these would not be issues however to do that would add weight and cost and possibly not be as shiny - all things that reduce sales of the product

How do I fit exhausts on most engines?
Permatex Ultracopper on the sealing faces, and a drop of Red Loctite on the bolts (the engine temp will weaken it adequately to allow it to be undone). Works for me !!

Tired Old Man

My Feedback: (1)

Lest we forget the dissimilar thermal expansion rates of a cast cylinder, a muffler flange of Lord knows what metal, and steel fasteners. Heat up, cool down, never at the same rates. Do that a few times and the gasket has gone from tight to loose along with the process. Eventually the process generates wear on the gasket from the movement of the muffler, allowing it to be blown out from between the two primary parts. Then you end up with a gap between the two parts allowing the muffler to slam back and forth on the cylinder. Then the screws start to wobble as they loosen up from the repeated muffler movement. As the screws wobble they destroy the threads inside their cylinder head bosses. Presto! You get to insert Helicoils if the boss design permits it, or worse, dump $100.00+ for a new head.

All because a gasket was used.

As Steve noted, the Ultracopper and some red Locktite has been proven successful thousands of time over.

pe reivers

On most engines nowadays, the flange is machined, so should be flat.
The headers however have a sheet metal flange. If using gaskets, that flange will distort, and the gasket is bound to blow after several heat cycles, even if regular tightening is practiced.
Fitting without a gasket, using a very thin layer of RTV well dried, will prevent flange distortion. The join may start to bleed some oil, but will never leak, nor will it loosen.

nonstoprc

My Feedback: (90)

What if the gasket is made of extreme-heat resistent material? Seems we are thinking of paper gasket?

pe reivers

??
Perfectly flat surfaces are tight without gasket.
A paper thin gasket (0.1mm) would probably be OK, but way too thin. If thicker as needed, it will cause flange distortion.
.

captinjohn

All exhaust gaskets are not made of the same material. Some are too soft. The gasket on my DLE30cc is made from a very hard material. I used it like it is...checked the bolts after running a couple of times...but not hardly any squish. The exhaust bolts stays the same tightness....and does not lossen up at all or leak at all near the joint. Capt,n

pe reivers

I agree with you John, IF the exhaust flange is stable enough and IF the gasket material is hard enough.
Those two IF's are two to many for most applications.

nonstoprc

My Feedback: (90)

I have been using the high temp. sillicon gel. It worked well for a while and then the exhaust gas breaks out at the weakest spot.

Seems nobody is selling after-market exhaust gaskets.

summerwind

Pe, do you mean to coat the surface, let dry, then assemble the muffler to the exhaust?

icabod

My Feedback: (29)

Thanks for all your good advice, now if I can just get this engine running to see if the sealant will work.

karolh

I simply do as the manufacturer recommends which is to put a thin layer on one side and let it air dry for 10 minutes before bolting together, and it works every time.

Karol

altavillan

My Feedback: (1)

Here's the trick to get a leak proof never get loose fit. Lightly sand a slight convex to the flange face. The center will contact first and the area around the bolts last. This way there will always be pressure applied across the whole surface. This same pressure keeps the bolts under tension and they will not back out. Make sure the opposite side is flat. Use a small amount of high temp silicone because if you do it right 99.9% will squeese out. Alow it to dry overnite before running the engine.

altavillan

My Feedback: (1)

.

pe reivers

See post #7

Altavillan is right as well.
In my two stroke competition days, the header connection always was a source of trouble, until we started using bare metal contact without anything in between the contact faces.
The sweat marks were a small price to pay come cleaning time.

summerwind

Pe,
i think you misunderstood me.......i'm not questioning you or altavillan.
i'm trying to understand the way the silicone is applied.
do i put the silicone on in a thin layer and bolt the parts together while still wet, or do i need to let the silicone dry first, then assemble?

pe reivers

In post 7 I advised "wel dried" It should be dry before fitting. Sorry for not writing a manual.
Apply as thin a layer as you can manage. (I dab it on) Too much, and it will squeeze out.

summerwind

LMAO.a manual would be nice though............thx, got it now (funny, i didn't see that before)

blikseme300

My Feedback: (118)

Be careful as not all silicone materials are safe to use on aluminum. Some types/brands are acidic and will "eat" the surfaces. Permatex Copper has served me well with no leakage or loosening mufflers on many engines over many years.

Bliksem

captinjohn

Hey...mabe a video should be made on the subject....and placed on you Tube!!!!

TheRickster

My Feedback: (12)

Clean both surfaces with thinner or brake kleen.. Apply a LIGHT film around the port perimeter.. Remember what squeezes out also squeezes in.. Apply a light film on the tip threads of the bolts as well.. Tighten it up and let it dry over night.. Never a problem..

Rick

pe reivers

I use loctite 596 red silicone gasket maker. never a trace of etching, and very good adhesion. To further improve adhesion when using it as a glue for muffler construction, I apply Bison silicon primer to the well cleaned bare metal first.