my 3" vband dp is leaking, is there a gasket i could use, or maybe gasket maker?

 

there are some cheaper brand v-bands that need a gasket, but most do not require it.

 

vband probably got a little warped when it was welded. Make sure clamp is on there evenly all the way around and tighten it down a little more and it should mate up and seal..

 

I think I've got the same problem, and I can't crank it tight enough to get it sealed. . . What is the best approach to gasketing one of these?

 

Yes, this is a common problem. You can always put a bit of permatex copper gasket maker on there and it will seal everything up nicely. Just make sure you give it 24hrs to cure.

 

are they the type of vband with the black viton oring? if so, use some vasoline around the lip of the flange.

like garage808 mentioned, some of the cheaper ones just butt up to each other, but the better ones will have a machined lip on one and an indentation on the other along with a viton oring to make for a perfect seal.

 

what about that copper gasket maker on my t4 flange? will that work?

 

The best bet is to resurface it if there is no alignment lip on the warped side(s). As long as there is enough thickness for the band to pull both flanges together it works fine.

 

when in doubt, high temp red rtv

 

That part of the DP will get above 600F on just the outisde -- the actual v-band surfaces will cook copper high-temp silicone to a powder. The best thing to do is have it decked (milled) flat. A large belt sander with fine paper would be enough, since it doesn't have to be perfectly flat like a head.