On Wed, 30 Nov 2005 00:34:42 GMT, "Clif Holland"
wrote:

I have a leaking coupling between 2 exhaust manifolds on a Cummins big truck
engine. Could it be brazed up to stop the leak. I don't really have time to
shut down and replace them right now. It is made of cast iron.

No. Brazing won't hold up to exhaust temps, particularly on a diesel.

It can be stick welded with nickle rod, TIG'd with nickle rod, or gas
welded with "railroad rod" and ferro-flux. The latter materials are
hard to find but would be my first choice. I've welded some tricky
cast iron with that stuff: some exhaust manifolds, an ornate
treadle from an antique Singer sewing machine and an ancient sewer
pipe grate that a friend wanted to preserve and restore in the
interest of authenticity in an old house with a lot of history and
character. She was an interesting person.

"Don, I have this cracked **** pipe so I thought of you." Who
among us could resist such a maiden's dulcet murmur?

Ya never really puddle railroad rod; you kinda mush it together,
working with metal in a plastic state. It takes a bit of practice
and it's not as quick as stick or TIG, but I've found that the job is
much less likely to crack, either in the weld or in adjacent regions,
upon cooling. Twerks fer me, YMMV.