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RTV for manifold gaskets or not??


CamoKing

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Amateur question here...I have a  set of Felpro gaskets for this '82, 720 w/Z22 engine .

The head gasket went on 'dry'.  I put some RTV on the timing cover  to hold in place while assembling. 

Now wondering if RTV is necessary on the manifold gaskets??  Or, are today's gaskets generally designed to go on 'dry'?    Thanks for any feedback on using RTV.

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If RTV was required Felpro would have put a tube in with the gaskets. If the mating surfaces are properly clean the gasket will do it's job. Using RTV is very unprofessional. It says...." I don't trust my work." Now in some cases, gaskets are no longer available, in other newer cars they never used them. In this, find a quality sealer.

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There are different sealants for the different areas of an engine too. Pet peev of mine - blue RTV. That stuff is worthless, and when you see it on every surface of an engine, you know it was pure amateur hour.

 

RTV or other kinds of sealers are not "unprofessional" at all. Improper or over use is, but knowing which to use on what part of the engine and then applying it in a manner that doesn't stand out, that's the key.

 

To answer your question about manifolds - It really depends on the manifolds. These are going on 50 years old now and the surfaces are probably not as flat as they were when new. If the surfaces have any imperfections (pits, scratches, somebody cleaned it with a Roloc disc, etc), then they need to be corrected, otherwise the gaskets will leak, RTV or not.

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I keep circling back to the "unprofessional" response. While a purist may not want to see any sealer, a realistic approach is to not want leaks.

 

A while back, I brought my 1964 Triumph Tiger Cub in to Mean Marshall's motorcycle shop in west Oakland to have him do some tuning. He is a purist and goes by the book, all the way. He's really good at what he does and has a reputation with vintage Triumphs. I had previously built the engine and sealed the crank case with ... um, crankcase sealer (Threebond 1211). It didn't leak a drop, which is unique for an old British bike. When I got the bike back he informed me that he tore the crankcase apart and resealed it with "proper paper gaskets". Guess what? it leaked.

 

I'd say it's rather unprofessional to not recognize the pitfalls and to not utilize all the means necessary to have a leak free engine.

 

Just as long as you don't see it.

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A Triumph is not a Jap made vehicle and no comparison what ever. They don't leak. If they were to leak you did it wrong, thus unprofessional. If racing, fine to waste time on a redundant layer of protection,  if just a regular car.... not needed.

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Pitting would have to be the width of the gasket used to leak. If that bad you would likely resurface or throw it away unless a chevy owner.. 

 

aoc5ndB.jpg

 

The cover was eroded the worst but I sanded them all down and used a home made gasket, dry. I guess I could have blobbed some RTV on it instead of fixing the surface, but that would be very unprofessional.

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So basically it's to hold a gasket it place??? Glue? It's really hard to argue that a gasket sealer leaks less than just a gasket doing it's job. RTV makers spend millions of advertising dollars convincing you that you need their product to do what the gasket is already made for doing. Incredible genius!!! There are places where it is good to use like where gaskets meet at a right angle and in some cases the gasket is no longer made or used and relies solely on a film of sealer such as a differential or transmission case. Funny how engines are built and run for hundreds of thousands of miles with no help from any sealer but suddenly a new gasket needs it?

 

 

If it makes you comfortable to use this stuff go ahead. I'm pointing out that you don't. In almost all cases when something comes apart it's a knee jerk reaction to get out the RTV. 

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You don't want a gasket extending out into any port and flapping in the wind. Exhaust ports have a metal ring around and to protect them from eroding from the hot corrosive gasses. I can't see anyone porting past a gasket match of this ring. Same with the intake though there is no ring, but the port and the manifolds don't always line up well from shifting of the cores when casting. You usually port out the the edge of the gasket on the head and the manifold, but in the case of an intake you can take it out farther and trim the gasket to match.

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11 hours ago, datzenmike said:

Pitting would have to be the width of the gasket used to leak. If that bad you would likely resurface or throw it away unless a chevy owner.. 

 

aoc5ndB.jpg

 

The cover was eroded the worst but I sanded them all down and used a home made gasket, dry. I guess I could have blobbed some RTV on it instead of fixing the surface, but that would be very unprofessional.

Very professional, Mike.

 

But we're not always taking about a small t-stat housing that you can hit on a belt sander. Try belt sanding a front cover or intake manifold. Even with a block of wood and emery cloth, these surfaces can't always be brought back to perfect. You've said it yourself before, these engines and parts are nearing 50 years old now.

 

 

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Of course use RTV if it's that fucked and you can't level it or have no choice, or ....don't use the part. Using on smooth clean surfaces is redundant if you have a gasket is my point. Far and away surfaces may be old but need just a new gasket. 

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As a 40+ year motorcycle and small engine mechanic I've had lots of experience with different types of sealers......used with gaskets and without (many engine case halves are assembled using only semi hardening sealants such as Yamabond 4, Hondabond 4 or Theebond 1184 all gray colored).

I tend to error on the side of caution  and use a very thin layer of sealant ( I say thin as in not seen when the part is assembled it's only there to supplement the main gasket not replace it) on most critical gaskets and it has worked very well for me for this many many years. Of course the sealants I use are gray colored as to not be seen so easily and anything that happens to squeeze out gets wiped off immediately with a rag or perhaps a drop of gasoline on a towel (easily done before it sets up, impossible afterwards) .......  I don't understand the fascination with using neon orange or blue RTV so much so that it squeezes out of the surfaces you're trying to seal! LOL 

As a Datsun owner and rebuilder of my own engines I can tell you they all were built the same way using either Yamabond 4 or Threebond 1184 on their gaskets,  they don't  leak and thats the way I like it 😉

Just one mechanic's way

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