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Long tubes > Y-pipe > High-flow Cat

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Old Feb 5, 2014 | 10:41 AM
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Default Long tubes > Y-pipe > High-flow Cat

I installed long tubes and got the expected stink. My plan was to install cats immediately behind the collectors, but the passenger side looks like it is going to be too tight.

Has anyone installed a high-flow catalytic converter between the y-pipe and the muffler?

Is this location too far downstream for the converter to be effective? I'm looking for stench reduction, not worried about emissions testing.

Focusing on a Magnaflow 59959. Magnaflow tech support was absolutely no help at all.
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Old Feb 5, 2014 | 12:16 PM
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i have longtubes and magnaflow spun metallic 3inch cats and i mounted them right after my longtubes. my passenger side i have plenty of clearance but my driver side scrapes. made a flat spot on the cat. As fow the gas smell, the cats helped out tremendously but i do have a little gas smell, but i made a tiny hole on the driver side cat because i was scraping so much. theres no other choices as for location because on the driver side the heat shield is located in the area where the cat is. any further back, the cats would be in the area of the fuel lines and i didn't want to have vapor lock
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Old Feb 5, 2014 | 12:48 PM
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Thanks for that.

I should have mentioned this is an 04 Silverado RCSB 2WD with XSP headers. You'd think there would be all kinds of room but the Y-pipe doesn't have any straight sections on the passenger side.
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Old Feb 5, 2014 | 02:34 PM
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Lots of older cars had a single cat in the I pipe. I think you'll be fine. I had good luck doing that on an LT1 car.
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Old Feb 10, 2014 | 10:21 PM
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If you have access to a Infrared Thermometer then check the temperature a few inches after the end of the header collectors, then at the Y-pipe exit. Now if the temperature difference is small then mounting a catalytic converter off the Y-pipe exit will still work fairly good, if not then don't waste you money or time.
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