4.2 Litre Exhaust Question

[dwyant30]

The flange that connects the header to the down pipe on my jeep appears to have a large chunk missing. I figured I would just buy a new down pipe, but my CJ doesn't have a cat. I'm having problems finding a pipe that goes from the header clear back to the muffler. Has anyone ever run into this? Is there someone that sells a pipe like this, or should I get a custom pipe made?

 

[IOPort51]

Is it a header or a manifold??

The flange that connects the header to the down pipe on my jeep appears to have a large chunk missing. I figured I would just buy a new down pipe, but my CJ doesn't have a cat. I'm having problems finding a pipe that goes from the header clear back to the muffler. Has anyone ever run into this? Is there someone that sells a pipe like this, or should I get a custom pipe made?

 

[dwyant30]

Is it a header or a manifold??

Well that goes to show you how much I know LOL! It is a manifold, not a header.

 

[IOPort51]

I have managed, in the past, to cut the flange off and reform it with a body hammer and round anvil. I have an old shot put that works really well but I could see a trailer ball working well too.

I was unable to find a muffler shop that could reproduce this flange but perhaps you will have better luck.

 

[54cj3b]

You sure it's not a ceramic donut thats whats on my AMC 258 i6 / 4.2l

 

[dwyant30]

You sure it's not a ceramic donut thats whats on my AMC 258 i6 / 4.2l

I wish it was. Either there wasn't one in place, or it had completly turned to dust. It is actually a piece of exhaust metal. My engine rebuild kit came with one and I placed it in line, but I don't believe it will ever seal 100% with that chunk missing.

 

[Rescue Diver]

You guys need to find better muffler shops. Any shop should be able to flare a piece of pipe to make that flange, and it should only cost a few bucks to get one made and welded to your existing pipe. When I went from the AMC 258 i6 / 4.2l to the 4.0 head and changed manifolds, my local shop only charged $25 to flare a new pipe and weld it to the existing exhaust. He even included a new larger diameter flange plate for that price....

 

[Cheepjeep85]

It doesn't use a doughnut gasket just a metal to metal seal that's it. Like rescue said a good exhaust shop can make that flare for you. If you don't have a good shop nearby quadratec, 4wd.com, and others sell the downpipe.

Droooiiddd 2

 

[dwyant30]

Thanks for all your help guys! I'm just going to go to a local shop and see what they will do. Might be a good time for an upgrade while I'm at it.

 

[Rescue Diver]

Thanks for all your help guys! I'm just going to go to a local shop and see what they will do. Might be a good time for an upgrade while I'm at it.

I'd stick with a smaller shop rather than one of the big chain stores, and try to avoid the shops in high end neighborhoods. You would be really surprised to hear price quotes from different shops for the same work. Even a lot of big chain shops will charge people in the ritzy part of town more than their stores in a poorer neighborhood charges.

You might also ask if they can do it with aluminized pipe. My local shop won't use plain steel, and my exhaust systems that they've done have never rusted.

 

[CJ]

I'd stick with a smaller shop rather than one of the big chain stores, and try to avoid the shops in high end neighborhoods. ~~~

When my last exhaust was done (years ago) it was done by a really rough looking facility. They did a great job. When it came down to payment time he asked if I needed a receipt... There seamed to be a nice discount if you didn't need on.

I said yes and then got a reply of - You know we didn't put catalytics on this Jeep, could be a problem. LOL. My reply was they didn't have any on my year.

I got such a kick out of the conversation we had a beer over lunch and worked out a great deal! They did excellent work and were the only shop that would attempt a complete inside frame, rear quarter duals.

 

[dwyant30]

So I guess in the mean time I should take the gasket out of their then? I've been battling gas ping so my attention seems to shift around a lot.

 

[Rescue Diver]

So I guess in the mean time I should take the gasket out of their then? I've been battling gas ping so my attention seems to shift around a lot.

Which exhaust manifold do you have? My stock 1979 cast iron manifold was machined for a donut gasket with the metal tube sticking out of it. When I bought a replacement manifold, it was just shaped like it already had a donut gasket in it, but it was actually the cast iron manifold itself that stuck out where the donut would have been.

Of course all that went out the window when I did the 4.0 head swap and switched to a later model Cherokee manifold.

If your stock AMC 258 i6 / 4.2l manifold is machined for a donut gasket, use a gasket, if it's already shaped like it has a built in donut gasket to mate up with the flared down pipe, don't use a donut gasket.

Got any pics of what you're working with? That would help a lot.

 

[dwyant30]

I'll see what I can come up with. The fact that the bolts were barely long enough to thread the nut on leads me to believe your statement to be true. When I took it apart for the engine rebuild, the down pipe was flanged to fit around the manifold outlet.