Here is a good thread https://dodgeforum.com/forum/2nd-gen...low-cat-2.html

 

Thanks for everyones input. In regards to 01's coming with a hi-flow cat, the factory would never have one that is as good as the aftermarket could be. I've heard alot of people who say the factory cat is still restrictive though, and that they often plug up. I'm hoping that the cat i put on there will be a cheap way to get a hi-flow cat put in my truck. I know it doesn't bolt up to the manifold, but i have some decent welding skills and i was figuring that i should be able to get that to fit in fairly well.

Can anyone tell me how much is this gona help the performance of the truck replacing the cat? What am i gona notice after putting it in?

 

since you are going to weld it on yourself, i suggest taking the y-pipe off the manifolds. its is a real pain to get a welder over the top of the pipe and actually get it sealed up. it might be possible with a mirror but it would be easier if you just took the y pipe off after running a bead along the bottom of the new cat for alignment purposes.

 

Where is a good place to buy new bolts for the y-pipe to manifold. If I have to take the y-pipes off I'm guessing it would be a good idea to replace these bolts also. I ordered the cat this morning for approximately $65 including shipping from amazon.com. Figured its worth my while to give all of this a shot.

 

I should mention i replaced manifold bolts in my dad's 96 that has a 5.2 and i don't know if i had the correct bolts, or did not get the exhaust lined up correctly, but it seems to leak a little. I want to be sure i don't do that on my truck, what are some hinters or things i should look out for so i don't do this on my truck too. I want to know what will be the best bolts to replace these with, and am i even going to be able to get the old bolts off? If i remember right we had to cut them on my dads truck with a torch.

 

You don't have to take the manifolds off in order to replace the cat. It would be a lot easier to just unbolt the y-pipe.

That being said, it isn't exactly easy to unbolt the y-pipe. Those 4 bolts (2 on each side) will be practically welded in there. I had to cut 2 of them and I snapped the head off of one with an impact wrench.

I just went to the hardware store and picked up a few new bolts that had the same pitch, diameter, and length as the old bolts. It's been over a year now and I have had no leaks.

 

Ok. I didnt know if i should get some sort of heat treated bolts or something. I'm thinking i might just use a mirror and weld the cat in as is. I've done some work on exhausts before and i think if i take my time with the welding i should be able to get the cat welded in with no leaks. Hopefully saving a little bit of the hassle of taking the y-pipes completely off. Are these hi-flow cats pretty beneficial on our trucks?

 

Unless your stock converter is plugged up, you won't see an appreciable increase from the replacement.

 

I noticed a definite improvement in top end, but that was about it. It's a great mod if you run in the upper part of the rpm range much, like when you get out to pass a car on the highway, or when your pulling up a steep mountain pass.

It's not the best mod in the world, but every little bit helps I think.