Catalytic converter problems

[rasouth]

I replaced my catalytic converter on my '78 less than a year ago and it is now busted inside. The mechanic said that it broke because there is a problem with the engine. He could not give me any more detail except that if I replaced the converter that it would happen again in a short period of time.
What could be wrong with the engine that it could destroy the converter in such a short time? I rebuilt carb and adjusted, tune-up, oil change, new timing belt and alignment, valve job, new head, intake and exhaust gaskets... Car seems to run okay; a little sluggish on cold mornings, once in a while little "popping" noises from tail pipe when I slow down...
Any ideas? I want to sell the car but I want to get it in the best reliable shape I can before then.

[majicwrench]

Converters can fail for a number of reasons. Simple mechanical issues, like coming apart inside, can happen. But many failures are because the unit gets too hot. They get too hot if the engine runs too rich. Converters can also plug from engine being too rich, and too hot. Any engine misfire will cause raw fuel to get into converter, and again, overheat it.
Just what is wrong with yours?? And what was wrong with the one you replaced a year ago??
Keith

[rasouth]

The old converter was old and rusty when I bought the car, so after giving it a tune-up and getting it insured I replaced the converter. It wasn't too often that I got a back-fire through the tailpipe, more often after playing around with the timing I would get one out of the carb until I got the timing corrected.
Now as of running rich, that might be my problem because it will make little popping noises when I decelerate, not enough to back-fire though.

[majicwrench]

SO what is wrong with the current unit??

[grittracing]

straight pipe forget the converter (and tune up)

[81SPIDERMATT]

will the straight pipe make it louder and where are they available

[grittracing]

I would say that you could make one from parts at a auto parts. or take it to a shop where there is a guy working by him self. (he owns and runs the shop )tell him you will pay cash and you do not need a receipt.

[majicwrench]

Scary. Good luck getting a shop to remove the converter. Even up here in the very NW corner of MT a local shop got seriously busted for doing that.

[rasouth]

Being in California I need the converter for smog purposes, so a straight pipe is out for now. The current unit rattles on the inside as if something is broken.
If this is caused because the engine is running rich, what's the best way to lean it out? Does timing have a lot to do with it? The car is timed about 5 to 7 degrees according to the marks on the timing cover.

[majicwrench]

The rattle inside may be because something just broke. May not have anything to do with being too rich. At this point I would change the converter and see what happens. If car has passed smog everything carb wise is likely OK.
With new conv, take car for a nice long freeway drive in the eve,, conv should be hot, but should NEVER glow. Shop should be able to hit it with a non-contact thermometer and tell how hot it is getting.
Again, if car runs well, I would just change unit.

Timing certainly has something to do with it. So do carb, choke, valves, everything under that hood. Running too retarded you will end up with fuel in exhaust = bad converter.
5-7 BTDC sounds fine. Is that specs??