Hi there,

I'm fixing an old Chevy C3500 Dually and I'm needing some help!

The exhaust manifold is broken, and I can't find parts for this truck here in Brazil.

The problem is: the original manifold has some pipes coming out of it that seems to be part of some system to reuse the fumes... I'm not sure.





I didn't find anywhere a manifold set like this original, and I'd like to know if I can isolate this "system" and use some other manifold, or if I must use an original one.

Can you help me to find the correct part?

Thank you!

 

Welcome from Florida. Looks like someone already tried to weld it. The manifold is available without the extra pipes. It is possible to get a manifold and have a very good machinist drill and tap it to reuse the pipes from the old manifold. What year and engine size do you have?

 

It would be easier if we knew what year and V8 engine size you have. You really need to replace those exhaust manifolds, if you can.

Those pipes that go into the exhaust manifolds are for smog control, which GM called the Air Injection Reaction or A.I.R system. They used a fan-belt-driven "Smog Pump" to inject air into the exhaust manifolds to burn up unburned fuel or partially burned fuel coming out of the engine exhaust.

If you don't need it, find exhaust manifolds without them, or you can plug them up as I have with steel plugs, while chucking the smog pump into the trash where it belonged. The SMOG pump does not handle dirt and dust well at all and won't last long if you drive in such conditions. The air-vane driven smog pump only depends on a plastic fan on the intake side to repel dust, but its usefulness in an off-road vehicle is very limited

The diverter valve will also cause lots of issues under such conditions. There is no air cleaner included with the A.I.R, system to keep dust out, so things will go bad in months, under dusty conditions, just as it would with any motor with no air cleaner. There are A.I.R. exhaust systems that don't use a SMOG Pump, but they are not in common use. Many vehicles these days use no such system at all.