Plugged cat cause knocking sound??

[Metrojunkie]

This morning I started my beloved 3 cylinder only to hear a disturbing familiar knocking sound. Sounds like rod bearing to me. i stumbled onto an ad that say a plugged catalytic converter will cause knocking. Here is where I viewed it. http://seattle.craigslist.org/see/pts/1454098070.html

I have never heard that before but it would be a wonderful thing. Second problem is not so much having to replace the bearings but what caused it. Nothing like fixing the broken part and not what caused it. sigh. The motor is all new, machined and lined honed.If someone were to have a constant hard work load on the 3 cylinder would that make it throw a bearing??

HELP, Please.

[1991_pontiac_firefly]

yes a plugged cat will cause knocking sound because it is damaging the valve so i recomend cutting off the cat and replacing it with a piece of straight pipe this will also give your car more power