RTV on exhaust gasket

bluerooster

bluerooster

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Seems to me that putting silicon sealer on exhaust gasket is an invitation for troubles.
Yet many airplanes have copious amounts of the stuff oozing out around the exhaust flanges.
I would think that it would burn out and cause leaks. Or is there a special kind of stuff that will not burn/blow out?
 
I installed my exhaust "dry" per the instructions that came as part of my builder's manual. I can't imagine using any kind of sealant on those gaskets.
 
From assembling racing engines: It is handy to use something as an adhesive to hold gaskets in place, making sure the exhaust ports are absolutely clear. When the exhaust manifold is torqued down any excess adhesive is squeezed out (hence "copious"), leaving an almost zero thickness layer between the gasket and the head face. Too thin for it to be a factor in sealing -- in my experience. I always liked Permatex Form-A-Gasket No. 2. That's the black glop that really doesn't harden. It cleans up with avgas or your favorite solvent, unlike RTV which seems to end up with a semi-permanent rubber film on everything.
 
But silicone for the adhesive? I would rather use the spray-on Copper form-a-gasket onto the gasket itself.
 
airdale said:
From assembling racing engines: It is handy to use something as an adhesive to hold gaskets in place, making sure the exhaust ports are absolutely clear. When the exhaust manifold is torqued down any excess adhesive is squeezed out (hence "copious"), leaving an almost zero thickness layer between the gasket and the head face. Too thin for it to be a factor in sealing -- in my experience. I always liked Permatex Form-A-Gasket No. 2. That's the black glop that really doesn't harden. It cleans up with avgas or your favorite solvent, unlike RTV which seems to end up with a semi-permanent rubber film on everything.
Click to expand...

On auto engines I have seldom used a gasket at all on the exhaust manifold. (GM hasn't used one for over 40 years) Much less any kind of sealant. I've also put aircraft exhaust gaskets together dry. But I've seen many with the RTV on them. And most of those were leaking. (I believe it's the "almost zero" part that's not zero had burned out) Which prompted me to ask the question.
I don't see the need to "glue" them in place, untill I can fit up the stacks. They seem to be pretty easy to install dry.
 
bluerooster said:
Seems to me that putting silicon sealer on exhaust gasket is an invitation for troubles.
Yet many airplanes have copious amounts of the stuff oozing out around the exhaust flanges.
I would think that it would burn out and cause leaks. Or is there a special kind of stuff that will not burn/blow out?
Click to expand...
Red RTV will char a bit, but still hang in there. We used to use it on exhaust systems for emission testing because at the California PZEV levels even a small leak can goof up the numbers.
In any case if it's squeezed thin, not much is going to happen one way or the other.
 
rtk11 said:
But silicone for the adhesive? I would rather use the spray-on Copper form-a-gasket onto the gasket itself.
Click to expand...
Pick your favorite kind of gooey mess and go from there. I hate sprays because of the inevitable overspray. Lots of people hate Permatex #2.

bluerooster said:
... I don't see the need to "glue" them in place ...
Click to expand...
Probably true on a street engine. On a racing engine typically the exhaust ports are enlarged and it's a little fussier to locate the gaskets.
 
For just holding them in place while assembly, we just use a small amount of vaseline. No need for any more aggressive sealant (I'd hate to have to disassemble an engine that someone decided to silicone or RTV the gaskets down).
 
I just wrap safety wire around a stud(s) with a tail to pull on.
 
Funny thing, the last time I had mine apart, I installed the cheapest, stamped exhaust gaskets that are like $1 each. Installed them dry as per the manual, and torqued them down. Work better than either the original asbestos type gaskets, or even the spendy blo-proof gaskets that I had previously used.

I had previously spent big bucks for the blo-proof ones, but after reading the sage advice of Harry Fenton, decided to go with the cheap OEM. I've never been happier!

V/r,

-Dana
 
The stamped gaskets are now about $4 each, and you need two per cylinder. Based upon that, I went with the ones that are $7 each, and only require one per cylinder.
 
bluerooster said:
The stamped gaskets are now about $4 each, and you need two per cylinder. Based upon that, I went with the ones that are $7 each, and only require one per cylinder.
Click to expand...

I purchased single-cylinder gasket kits (Connie o-300) about six months ago, for $9 per kit. Included two of the stamped gaskets, plus everything else.


Part Information
Part Number: SA200-T1

Pricing Information
List Price: $16.38
You Pay: $8.72

YMMV!
 
The people who put RTV on exhaust gaskets are the same people who use Teflon tape on AN hose connections, people who have no idea WTF they're doing or how things work.
 
Silvaire said:
The people who put RTV on exhaust gaskets are the same people who use Teflon tape on AN hose connections, people who have no idea WTF they're doing or how things work.
Click to expand...

Hmmm................. And, when they buy the ranch because of it, their families sue.
 
Silvaire said:
The people who put RTV on exhaust gaskets are the same people who use Teflon tape on AN hose connections, people who have no idea WTF they're doing or how things work.
Click to expand...
Or any kind of flare or compression fitting. That just chaps my azz, to see someone doing that.
 
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