.:.

When I was changing my O2 sensors yesterday I noticed that the exhaust right below where it connects to the header is dented pretty bad. It is dented also on the opposite side of the one pictured. Seems like that would affect flow and likely performance, but I could be wrong.

Anyway, my question is what do you folks think is the best way to go about repairing this?

I need to get a bung welded in for a Wideband AFR gauge in the next couple days right around in that area so I think it's something I should probably take care of.

XjJunky

Those are there from the factory. Best fix is jave a shop custom make you a new pipe. Mandrel bent is best for flow if you know of a shop in your area that bends pipe. Don't forget to have them weld in a flex pipe too, helps keep the exhaust manifold from cracking.

.:.

Why would that be there from the factory?

EZEARL

My understanding is Chrysler did it to preheat the catalytic converter and make it more efficient, leading to a better emission standards rating.

XjJunky

Exactly

dave1123

Guys, just off the cuff, I'm an old gearhead and all for maintaining Federal standards, but deep down I really don't give a "FF" what comes out the tailpipe as long as it doesn't attract too much attention. How about you?

caged

there was a video years ago about how these dents affect the flow. short story is, it doesn't.
they took a set of headers and smashed them in almost flat, and it didn't change the numbers very much at all.

i used to have a 67 dart with a built 340 with headers. i smashed those things off every speed bump. dented them in pretty good. i was always worried it would affect the flow, until i watched that video many years later.

EZEARL

^^^^^^^^^^^
I bought a '69 Dart (GSS) from Grand Spaulding Dodge in Chicago (Mr. Norm) with the 440ci engine.

.:.

Very interesting.

Can this thread be locked for talking about this? I saw the updated rules, but the link to what the rules actually say did not seem to work.

Well if EZEARL is right and they did it from the factory to preheat the Cat then it definitely affects flow. Maybe I am wrong about that. Could you please explain to me how it is expected to preheat the Cat? Do you know where I can find that video? I really want to see it.

EZEARL

I don't know what the negative effects if any would be if the dent was eliminated (maybe to the computer performance?) but the factories only option besides that dent was to install two more cats (pre-cats) such as is on the Calif equipped XJ's.

cruiser54

Renix had dents also, as they all did.

I was told directly by a field engineer who worked on emissions certification for the original 4.0 that the
dents" were there to heat up the cats sooner.

XjJunky

Does not mess with your computer at all. Just makes for a free flow exhaust. Stock pipe is 2.25" if you jump to a 2.50" pipe about the only negitive is a small and i mean very small loss in low end torque. Not enough you will even notice unless you dino it

Cummins93

I eliminated my dented downpipe when I added my supercharger setup. Out of boost performance stayed the same. My cat was gutted so it's an un needed option. I'm not sure how flow would be affected with the added exhaust volume from the SC.

.:.

Yeah, based on these responses I think I am going to just leave it... for now. That money could be better spent on something else for the Jeep.

EZEARL

Good call. You could always up grade later on as needed. I went to a 2 1/2" cat back system upgrade when my OEM muffler gave up the ghost.