1991Jeep_Man

My cat is old, clogged, and just disgusting on my '91 XJ. NOW, before anyone goes on a tangent with "cat removal" and what not, I know the rules and the laws and have ZERO intention simply gutting my cat or removing it. I already have a new high flow cat from mudfrog, I just dont know how to mount it, but I have an idea. See, I have this wierd flange thing the front of the cat mounts to. Would it be ok to cut the pipe right before the flange to remove it altogether, and then have my 2.25 to 2.5" adapter right there? Or does the flange serve some mounting purpose?

Also, do ya'll think a jig saw would cut through the pipe? I have a metal cutting blade and the saw is a descent powered Black and Decker which I've used to cut a 1/8" thick piece of steel before no problem. Thanks for all the help everyone.

TheDale

Sawzall is your best bet for cutting exhaust.

Alot of times you can just use SeaFoam engine treatment and it will clean the cat pretty good.

You really need a solid mount, if their is a exhaust leak, the cat won't function. You need to either weld it back in, or mount it with the flange.

A Catalytic converter doesn't just fail. Their has to be a running issue for the cat to fail. Bad spark plugs, clogged air filter, leaky injector, etc... Fix that issue at the same time or you will be replacing your cat in the very near future.

1991Jeep_Man

Well that sucks. I lack a sawzall...

And the cat isn't neccesarily clogged. It's just old, and the casing is looking rusted and ancient. Plus, the stock cat I've heard is a big choke point in the XJ's exhaust. The high flow cat will compliment my 2.5" exhaust, flowmaster Super 44 muffler, and my bored TB.

TheDale

Oh ya, definately, these old cats are a joke compared to a good new one.

Your best bet is to find a shop that will weld it on for a decent price.

MWildmann

No offense Dale, but i'm not sure i agree with you. I just got done putting my new hi flow cat and cat back on about a month ago. I had a welder on hand to do the job, however, the cat was stainless and the remainder of the exhaust was stock or aluminized. Didn't know if i could weld it in or not, so we just clamped it in. Haven't had any issue with leaking or having it come apart on me. I will not say that you are wrong, welding is always first choice, but i don't think its the only option...

splitime

Mod what you need to make it fit honestly. My magnaflow came with a flange in the box that could be welded on, I assume older models at some point had a flange from downpipe to cat. Mine was a slip fit, so once I cut notches in the stock cat pipe...pried it open some and wiggled it off, then I just slipped the new cat on.

dukie564

cut off the flange and old cat - it's the only good way

i used all clamps on mine with no issues

bigvig

Same here: All clamps, no issues.

Gee oh Dee

Lots of OEM replacement setups use clamps, not just for XJs. Welding is nice, but not the only way.

Smaller holes may eventually get plugged by the exhaust gas deposits. May.

1991Jeep_Man

Thanks for all the help and idears guys. I appreciate it. As soon as I can find a friend with a sawzall, Im gonna dive in. I'm going with clamps and some really high temp exhaust pipe sealer to go on the pipe inserts.

If ya'll wanna have some giggles, I had planned on doing this project at my friends house. I was sitting with him and his grandmother in the kitchen, discussing how to go about mounting it, and all of a sudden his grandmother flips out on me. "YOU CAN ONLY HAVE A SHOP PUT A CATALYTIC CONVERTER ON! YOU WILL BE ARRESTED!". I know technically a shop is supposed to do this, but I mean really? Will the world end if I do this myself? No.

Gee oh Dee

Why would you het arrested? Some people....

You could use a grinder with a cutoff wheel as well.

1991Jeep_Man

Alright, so another quick question. Would a High Flow Cat get near 1000*F? The sealer I bought doesn't "rock harden" *insert joke here* because I may want to take it apart later and reroute or weld, and it is for high temps up to like 700* or something like that.

1991Jeep_Man

Got everything on and hooked up. The clamping is rediculous, but everything is sealed, sounds great, and now the engine is DEF breathing better. Took a steep hill today and never dropped out of Overdrive like I would before. Thanks for all the help everyone. I didn't use any sealer, just tightened the clamps good. To anyone with a '91 XJ, the downpipe is 2" before the cat... I found out the hard way and this resulted in the many clamps with many adapters lol.

freegdr

did not drop out of over drive depend on how steep the hill was i think it should drop down

thehuff

I need to do this soon as well, as soon as new exhaust arrives. I already got a new cat. The old cat I was trying to remove the O2 sensor and instead of the sensor coming out the whole thing ripped out of the cat. And the muffler had a bad leak and needed to be replaced...anyways this is what put me over the edge.

I'm guessing the old cat is rusted on to the downpipe quite well. I was thinking I'd cut the old cat and exhaust free near the body of the cat with cutoff wheel or sawzall, then seeing about freeing up the slip part. How'd you get yours off?