A good exhaust flange sealer?

Bonnewagon

Geezer
Sep 18, 2009
8,135
113
Queens, NY
I have the single exhaust head pipe that has the four bolt flange where the CAT bolts up. I have no CAT but I am using a cheater pipe with that same four bolt flange on the end. I have the correct thick aluminum gasket. The head pipe flange is in pretty bad shape. I wanted to use some kind of sealer to make sure there is no exhaust leak at the flange. What will seal well but not go bad from water or other abuse?
 

buick7332

Master Mechanic
Oct 21, 2014
271
63
N.E. Philadelphia area
I have the single exhaust head pipe that has the four bolt flange where the CAT bolts up. I have no CAT but I am using a cheater pipe with that same four bolt flange on the end. I have the correct thick aluminum gasket. The head pipe flange is in pretty bad shape. I wanted to use some kind of sealer to make sure there is no exhaust leak at the flange. What will seal well but not go bad from water or other abuse?
I had a similar issue and used this.
 

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oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,822
113
mpls
permatex ultra copper rtv.
 

Bonnewagon

Geezer
Thread starter
Sep 18, 2009
8,135
113
Queens, NY
I tried the red years ago and it was OK but not on exhaust stuff. The ultra copper sounds better- good to 700°. I used to use the spray copper gasket seal but usually on head gaskets. Thanks!!
 

motorheadmike

Geezer
Nov 18, 2009
7,825
113
Aberdeen, Saskatchewan Canada
I've skim coated stubborn flanges with muffler cement. But, most often high temp copper RTV gets used.
 
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Bonnewagon

Geezer
Thread starter
Sep 18, 2009
8,135
113
Queens, NY
I've skim coated stubborn flanges with muffler cement.
I ended up doing just that. I even had to use a split flange to have enough to bolt the new pipe to. The head pipe flange was worse than I thought. It is impossible to get a single exhaust head pipe for a Pontiac V-8 anymore so I have to make this one last. The muffler cement was good to 2000° so that is what I went with.
 
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motorheadmike

Geezer
Nov 18, 2009
7,825
113
Aberdeen, Saskatchewan Canada
I ended up doing just that. I even had to use a split flange to have enough to bolt the new pipe to. The head pipe flange was worse than I thought. It is impossible to get a single exhaust head pipe for a Pontiac V-8 anymore so I have to make this one last. The muffler cement was good to 2000° so that is what I went with.

I think I just threw two of those out. :eek:
 

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