I just got a heavy duty 93 F250 4x4 with a 351/E4OD combo and over 200k miles. The PO put on a new muffler and short tailpipe after the stock cat but everything else seems to be original or pretty old. It has an exhaust leak that I am not sure if it is the gasket between the Y pipe and the cat or from the front tube of the two tubes that run in to the top of the cat. The front tube is completely rotted in half and no longer connected to the cat. First what are these tubes for, I believe they pump air or oxygen into the cat??? Second if they are removed or blocked off does it affect emissions or would I still pass inspection? I was thinking of putting on a new cat anyways as this one seems pretty old and is probably clogged up but a direct fit one from NAPA is $600!!! I found cats at some other places for under $200 including a Catco one from Summit racing that is suposed to fit, does anyone have experience with this cat any other ideas? The exhaust leak really makes the truck sound like crap which is a shame cause it runs nice otherwise.

 

anyone got any ideas??? I want to put a new cat on anyway but I just need to know what these tubes are and are they easily replacable?

 

The tubes bring air from the air pump into the reaction bed in the catalytic converter. Air is 20% oxygen, and the cat reacts the oxygen with HC and CO in the fuel to produce H2O and CO2.

If the tubes are not connected, the cat will not work very well, if at all. It will probably fail emissions. It will eventually clog up if operated this way. With an audible exhaust leak, it should fail any emission test based on a visual inspection alone.

You could try fixing the front pipe. If it is rotted in half, that is probably the source of the exhaust leak that you hear. The Catco cat should work fine as a replacement, should you go that route.

 

I can agree with Fefarms 150 %. With my smog/air pump inoperative (because I'm still looking for replacement solenoid/actuators) I installed my replacement cat converter (CATCO brand) and my emissions readings actually increased!! And only after removing the old cats did I learn that the previous owner had hollowed the originals out. Yes, I had lower readings with NO cats...kind of surprising....??
fefearms knows