Exhaust question

[elwood blues]

Re: Help - Carb Intake Exhaust

The intake manifold you need looks like this; notice how it bolts together to the exhaust manifold? The '80 and newer intake and exhaust manifolds do not bolt together, there are differences in the alignment tabs on the heads of the '72-'79 AMC 258 i6 / 4.2l 's that won't allow you to use the new manifold unless you grind them down.

 

[dtrojcak]

My new to me 1978 Jeep CJ7 AMC 258 i6 / 4.2l has cracks in two of the six exhaust header pipes. Both cracks are where it makes the first turn down a couple of inches away from the engine.

I've looked at several different websites for exhaust headers and manifolds.
I'm having problems locating the "down pipe" that connects the manifold to the pipe in front of the muffler.
I'm also having problems locating the pipe to connect between the header(s) and the muffler.

I was thinking of replacing the entire exhaust from the engine to the tailpipe, but I can't seem to find the second section on any website.
Do I need to go to an actual local muffler shop to get the missing pieces?

I am also undecided on whether to go with headers or a manifold.
Headers are more expensive it seems.
What actual improvement(s) does a header have over a manifold and is it worth the added cost?
This will be a daily driver, run around the deer lease type vehicle. I have no intention of rock crawling or any serious off-roading type activities.

 

[IOPort51]

I run a header because of the 4.0 head conversion. I, personally, see very little advantage to a header over the manifold on a stock AMC 258 i6 / 4.2l head. I would suggest a manifold from an 89ish AMC 258 i6 / 4.2l , this will not have a "donut gasket" but rather a cast and machined exhaust pipe mating surface. You may be amazed at what your local shop can do at a very reasonable price.

 

[elwood blues]

Here's the deal with the AMC 258 i6 / 4.2l 's, pre 1980 the intake and exhaust manifolds bolted together, 1980 and newer the intake and exhaust manifolds are two separate pieces. So, that being said, if you're still running your stock intake manifold you have to either run a header or a stock pre 1980 exhaust manifold. Unless you want to change your intake manifold as well.

When I replaced my exhaust system a few years ago, I bought a stock replacement exhaust manifold online and the headpipe and tailpipe from NAPA, and a Flowmaster 40. I'll see if I can dig up the thread.

 

[dtrojcak]

Here's the deal with the AMC 258 i6 / 4.2l 's, pre 1980 the intake and exhaust manifolds bolted together, 1980 and newer the intake and exhaust manifolds are two separate pieces. So, that being said, if you're still running your stock intake manifold you have to either run a header or a stock pre 1980 exhaust manifold. Unless you want to change your intake manifold as well.

When I replaced my exhaust system a few years ago, I bought a stock replacement exhaust manifold online and the headpipe and tailpipe from NAPA, and a Flowmaster 40. I'll see if I can dig up the thread.

Looking forward to that info.

 

[elwood blues]

Well, that didnt work like I thought it would. I apologize for that post I pasted in to this thread going there.

There's some good info there, there's more in this thread too;

http://www.jeep-cj.com/forums/f49/83-cj7-front-exhaust-pipe-options-needed-19311/

I've got to run, if this doesn't answer all of your questions, let us know, I'll be back later

 

[dtrojcak]

Well, that didnt work like I thought it would. I apologize for that post I pasted in to this thread going there.

There's some good info there, there's more in this thread too;

http://www.jeep-cj.com/forums/f49/83-cj7-front-exhaust-pipe-options-needed-19311/

I've got to run, if this doesn't answer all of your questions, let us know, I'll be back later

I'll try to take some pictures of what I have tomorrow and post them up for clarification.

If I went to NAPA and got a 6002439 exhaust manifold, would it bolt up to the 45661 head pipe?
Then I would just need a muffler and tailpipe after that, correct, or am I missing something else?
My muffler doesn't have any holes, but the output side looks like the pipe rusted off. The muffler is quiet, but there is no tailpipe coming out of it, just a hole slightly bigger than what the pipe would be. The exhaust exits directly onto the rear axle.
I figure the extra heat on the axle isn't doing any good and I might as well replace the entire exhaust system while I'm at it.

Thanks for all the advice and help so far.
This is my first Jeep. The PO repaired a lot of the bigger things, but it seems there are a lot of "little" things left.
I will definitely be relying on the knowledgeable people on this website for several things in the near future.

 

[elwood blues]

Yes, the 6002439 appears to be the correct manifold. But, search the internet, $299 seems a little high, I bet if you shop around you can find one closer to $200. Believe it or not, I've never had an issue with NAPA exhaust stuff, you could probably go to your local store tell them what you have and they could order you everything, including a not too expensive muffler.

Are you currently running a catalytic converter? That will change everything if you are

I'll wait until you post some pics and we'll go from there.

 

[dtrojcak]

I was thinking that price was high. I've found headers for about the same price online.

No catalytic converter, so that should make it simpler I'm hoping.

Again, thanks for the advice, at least now I know what direction I need to go.

I'm hoping to get it street-legal by June.
I was able to get the blinkers working on Monday.
Now I need to get the exhaust fixed and replace the wiper blades and I should be able to pass inspection.

 

[dtrojcak]

Amazon has the same manifold for $174 + free shipping.

Amazon.com: Dorman 674-235 Exhaust Manifold: Automotive

 

[73CJ]

Lots of good used cast ones out there.

Ok if interested in used. Cheap.

 

[IOPort51]

4 2L 6CYL Exhaust Manifold Jeep Wrangler 1987 1990 CJ 1981 1986 | eBay


one more option, problem with cast iron parts is that shipping is a killer.

 

[dtrojcak]

Instead $80+shipping for a used one from some stranger, I think I'll spend $174+free shipping for a new one from Amazon and hopefully not have to worry about it breaking for a long time.
Thank you got the suggestions though. It gives me options.

 

[JimsCJ5]

Oh Hell no.
Ditch the ridiculous mated intake and exhaust for an aluminum intake and the later model exhaust manifold. I bought my new exhaust manifold off eBay for 65 and the aluminum intake for another $20. Added a late model throttle cable , bracket and hose fittings and I was good-to-go.

Also went to my local muffler guy and he hooked us up with an all new custom exhaust system including 40 series Flowmaster for $260.

 

[Dan77CJ7]

Amazon has the same manifold for $174 + free shipping.

Amazon.com: Dorman 674-235 Exhaust Manifold: Automotive

check the review.....

 

[dtrojcak]

check the review.....

The one?!?

 

[dtrojcak]

I just realized I never posted pics of what I have.
Looks like I have an Offenhauser intake manifold and from what I can tell, Pacesetter headers.
Does the Offenhauser intake restrict me to a "mated" exhaust manifold like the OEM intake does?
At this point I am undecided if I want to install a OEM style manifold, or to drop the coin and get a set of Borla headers.
The Jeep will not be used for any rock climbing or anything like that, just a semi-daily driver. It will probably mainly get used as a "ranch truck" at the deer lease.
Would headers be necessary and/or would they give any worthwhile performance improvements over a manifold?

 

[dtrojcak]

I'm leaning towards getting a set of headers.
I've found that the uncoated ones are not much more than a manifold.

I'm looking at either the Hedman 99600 or the 99610 headers.
It seems Summit has the best prices, but I can't find the pipe that goes between the header and the muffler.

I've looked on several different websites with the same results.
I can find the header, muffler, and tailpipe, but not the front pipe.

 

[dtrojcak]

Is there any online retailer that sell the entire exhaust system?
I cannot find anyone who sells the front pipe that goes between the headers or manifold and the muffler.

 

[mtnwhlr]

You may just need to take it to a exhaust shop and have them do it. A good shop can make anything.