Catalytic Converter

[Bryan G]

Thought: I had a pickup built in '74 that had a factory air pump but no converter. The lines to the manifold were in poor shape and the old pump rattled so I pulled it all off. I was surprised how much it changed the smell of the exhaust. With the pump it had that "malaise-era" odor! So, yes, it was doing something. I'm guessing the air has to be introduced up close to the engine which wouldn't be pretty.

[Tooljunkie]

1 hour ago, Bryan G said:

Thought: I had a pickup built in '74 that had a factory air pump but no converter. The lines to the manifold were in poor shape and the old pump rattled so I pulled it all off. I was surprised how much it changed the smell of the exhaust. With the pump it had that "malaise-era" odor! So, yes, it was doing something. I'm guessing the air has to be introduced up close to the engine which wouldn't be pretty.

A.I.R. Systems used a convertor. Air was introduced to aid in the burn off of emissions. Back then, the systems werent very efficient, and those air pumps were prone to failure. Yet some seemed to last forever. 
 

those pumps were used by small engine racers as a supercharger of sorts. 

[Dartgame]

Look at a 1975 vintage straight six - like a chevy or Ford 230 or a mopar slant 225 powered car. Go to rock auto or other and look up the size and type catalytic converter those used, that should get you there. I know for certain chrysler products did not use an air pump in the US outside of California. They had a few vacuum gizmos on the distributor to change the vacuum advance and an EGR valve but none of those would affect the Cat and its effectiveness. 

 

I suspect as others have said; a razor sharp tune should clean up the exhaust, set the dist at about 5 BTDC, and adjust the valves. Additionally use a stronger spark ignition, like an electronic distributor retrofit and use a Ford EEC IV coil. Lots of spark energy ! GM did this too, to help clean up their exhaust emissions in the mid 70's.