Why would you even want a rusty header pipe connected to your new engine?

I don't think the flange has to be welded to a new pipe. It can just slip over the header pipe and stop at the flared collar.
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Are you sure the old one is welded? Maybe it's just rusted in position.

Last edited by Otto Skorzeny; 03/10/2022 1:30 AM.
1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)