Best RTV for exhaust manifolds?

kyle41005

New Member
Sep 23, 2010
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Just got my exhaust manifolds back from machine shop. Wanting to bolt on but wanted to ask what rtv have people used that they can vouch for. I was considering 3 different ones. All permatex. High temp red I think is good for 650 degrees, ultra copper is about 700 and they also have a "muffler sealant" rated for 2000. Anyone ever use these or another product they can recommend? And before anyone tells me to use gaskets, I can't. Motor is a 78 and they don't make any performance gaskets for this motor. Just ones that have a reputation for blowing out which is why I am going gasketless and had manifolds machined.
 

jasjamz

THS Racer
Sep 30, 2004
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Ultra copper and have the mating surface smooth then use even torque to tighten them down.

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CS99

Member
Nov 21, 2002
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How does ultra copper last if it only rated for 700 degrees?

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No disintegrations

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Dec 27, 2015
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How does ultra copper last if it only rated for 700 degrees?

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The flange does not get as hot as the exhaust gases. The coolant in the heads and all the iron or aluminum pull heat away from it too fast to build that kind of heat.
 
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earlbrown

runs with scissors
May 26, 2001
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Use whatever silicone/RTV you have that hasn't solidified yet. It's not going to matter.

The end result comes from the actual application, not what color dye the goop has in it.
 
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earlbrown

runs with scissors
May 26, 2001
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If you just have to have colors, get the red. The red dye is rated higher than the copper dye.


Not that it really matters. Anything is better than nothing and the factory didn't use anything.
 
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