Catalytic Converter Replacement, 99' 5.0 Mounty

[tomtom1427]

Started off with a CEL and a lean code for bank 2. Come to find out that the exhaust pipe between the manifold and the catalytic converter has begun to look (and sound) like I was trying to direct my exhaust gasses to the rear of the vehicle VIA a piece of swiss cheese. SO... Im replacing the cat with an OE replacement as it comes with all of the pipe and the flange as one piece. My questions are...

1. Is it really terrible to only replace the cat on one bank? I will absolutely be doing the other one, it just might not be for a month or two. I have no reason to believe that the cat on bank 1 is bad, I just know that its generally a good idea to replace these things all at once.

2. What are my chances of getting the flange bolts out where the old pipe meets the manifold? Any tips, tricks, or personal experiences? Were talking about a north east truck with 180,000 miles on it...

 

[RandomNerd2000]

All I can provide advice about is the bolts, had to do a set recently on a Maine truck, one came off, 3 rounded, but I have reason to believe the wrong thread nut was used. Soak them well in the ATF/Acetone mix, you won't be sorry.

 

[96eb96]

Very unlikely they will come out in one piece from where you are. Your only hope is either mapp or aceleltene on the flange, then wax, and every penetrant under the sun to try to free up the threads. The bolt head is likely destroyed, you will probably have cut the bolt and take it out with vice grips. I don't know the V8 but on the V6 it isn't easy to get to.

You may want to pay a shop labor to replace those studs. I know some won't touch anything with cat converters unless they do the whole job.

Finally, there are always these: https://www.amazon.com/Exhaust-Stud-Clamp-Kit-Trucks/dp/B00E4TMK60

 

[RandomNerd2000]

I didn't know they made exhaust kits like that, that's a nice idea, assuming engineers and their infinite wisdom remembered a place to access the studs. I have a V8 parts car I'm gonna swap into another body due to a wreck, it doesn't look horrible, but not great either, I will say that it being an SC car since new means it looks amazing underneath

 

[tomtom1427]

I ended up taking it to a shop. Both bolts snapped and they had to drill and replace them both. Fixed my lean code and all is well... Just need to replace the cat on the other bank now.