flashsplat

So im a total noob here. I literally just bought a tool set and started taking crap apart on my jeep becuase I couldn't find anyone that would replace my head gasket for a good price...

Anyway. With the header off, I noticed the exhaust looks bent. Is this normal?





bend, or bump in the exhaust where it connects to exhaust manifold

jay_sco

Yes, came standard on XJ's. Something about emissions, they dented it to build up heat in the cat (or pre-cat) faster...something like that.
It's been discussed on he interwebz numerous times, IIRC it makes a very minimal difference in power output with the 4.0, so little that it's not worth the trouble to custom make a non-dented version.

flashsplat

ok cool ty. I actually dropped my cat but won't bother with a new exhaust if theres no benefit. Seems strange to have all this "More air in, more air out" stuff and then have a bottleneck right out the gate..

CCKen

Actually, I think that is to clear the front drive shaft when doing some wild off road stuff.


A dent in the exhaust pipe upstream of the CAT will not preheat the CAT. It doesn't need preheating.

xjferrell

just replaced mine. make sure there are ZERO holes in it lol. i put mine on and it had a small hole (gap) in it where the two pipes come together and every time i start theirs a faint whistle. no engine difference but annoying as hell

jay_sco

Quote from another thread on this forum. I've read it's to increase back pressure for torque, or for emissions, or for clearance. I'm not sure if anyone knows for sure. The only thing I know for sure is it is normal on XJs. Not due to abuse by a previous owner.