Catalytic Converters?

[hemi43]

What engine are you using? You can't just put catalytic converters on and expect them to last especially with a carb. They need oxygen to work either by the use of an air pump or one way valves that suck air into the exhaust.
The best thing you could do is get rid of the antiquated carbureted engine and install something late model. At the very least, get rid of the carb and get fuel injection.