Alfetta exhausts

[James Montebello <jamesm@domain.elided>]

My Alfetta coupe needs a complete exhaust system.  Everything aft of the
manifold is rusty, and the cat has developed a bad rattle.  This is a
CA model '78, so it has the 4-2 cast manifold with an air pump.  I have
a two-piece cast manifold on the shelf with resembles the European parts
I've seen photos of.

Q: the US manifold has the 2 outlets side-by-side, whereas it *appears*
the only way the Euro manifold will go together properly is with the
outlets front-to-back.  This correct, or am I simply holding the parts
wrong?

Q: the 2-piece manifold has threaded holes that look like air-injection
points, and all the photos I see of these things assembled shows them
filled with bolts.  Will the US air pump plenum bolt to the Euro manifold?

Q: anyone have any hints on how to remove the air pump plenum without
damaging it?

Q: if I remove the hose from the air pump to the plenum and start the
engine, faint pulses come *out* of the hose.  I assumed the valve
behind the head was a one-way valve to prevent the exhaust from coming
out, and only let air in.  Would this mean the valve is bad?

Any and all answers welcome,

james montebello
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