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Exhaust Manifold vs. Headers

2927 Views 6 Replies 5 Participants Last post by  STJP
I have a 78' CJ 258. I am upgrading from a one barrel to 2 barrel. Which requires an intake Manifold from a newer model jeep. I got all that covered. This project has been going on for 10 years... but finally getting it done. SO many moons ago I purchased headers for a dual exhaust system.

1. Do headers make a difference performance-wise?

2. There is one spot where the header will not allow a proper fit for the intake Manifold, and one spot where it's too big for the power steering pump. So I'm wondering if I could take a sledge hammer and pound the steel header a bit to allow the fit? So if one header tube/or two is flattened out a bit... does this make a different in how it will run?

3. I had headers before... and they where a pain in the... ! Am I just better off going with a new after market exhaust manifold that matches the intake manifold?
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1. Yes, it will improve performance. You probably will have to make some adjustments to the carb and ignition but yes, it will make an improvement.

2. A little dent here or there won't have much of an impact.

3. Depending upon the headers you by, they could rust out. The rest of the exhaust will always be a custom fit. You might get tired of the noise. As they get hot, they will heat things near them up also like your power steering pump. It's always fun chasing after header gasket leaks.

Which one did you buy?
 

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John is correct they will make a performance difference, but is the small increase worth the trouble. The 258 is a great low rpm torque engine, but as JeepHammer has opined, it is a tractor motor.

If you stay with a OEM exhaust manifold (as I think you should) and need any info re fastener size etc, send me a PM or post a question.

JS
 

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Discussion Starter · #4 ·
Awesome... thanks for the feedback! OK... I've decided to eat the cost of the headers and go with a OEM Exhaust Manifold. Which leads me to a new question. A couple of the major Jeep part websites list two different exhaust manifolds... and the price difference is about $75. Is one that much better than the other? The more expensive one doesn't even have a brand name associated. The cheaper one is from OMIX.

Also, please excuse my ignorance... it seems they send two different gaskets with these. One that goes across the entire intake and exhaust manifold area... then another that only covers the exhaust are. Am I supposed to double these up? And the gaskets have a metal side to them. Which side goes toward the block?
 

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Headers pretty-much always improve performance over the stock stuff. The challenge is knowing what primary size to use, what exhaust port csa, what length, what secondary diameter and length, is what I need even available?

Sometimes the only thing you can find through the aftermarket is a 1.625 x 40 with a 3 inch collector when what your engine really needs is a 1.45 x 48 with a 2.125 collector tapered out to a 2.7 final size with an anti-reversion step over the course of 24 inches. Good luck with that. Now you have a decision to make; The sub-par header or the horribly sub-par exhaust vs how much you can spend without having your wife kill you in your sleep.

The biggest headaches I've personally seen from headers is leaks. Gaskets are gaskets no matter what two materials you're hoping to seal together, right? With a header, you can't reef down on the fasteners like you can with a chunk of cast iron. Don't ask me for a specific torque value but a grunt and a half from your average Craftsman ratchet seems to work well.

The key to making them seal though, is hitting the fasteners again after a few heat cycles. And then again tomorrow, and then again on Thursday, and then again next week just to make sure. And don't over-torque them to begin with. They'll never seal that way.

If nothing else, it gives you an excuse to sit in the garage and drink beer.


Shawn
 

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These manifolds are not difficult to find on Ebay. The 81-86 manifolds do not have ports for air tubes from the pulse system. Many of the aftermarket manifolds show these air pulse system tube holes plugged with bolts I think.

Pictured is my used exhaust manifold before and after cleaning. Notice closed air pulse system holes sealed OEM/factory.

One gasket is for exhaust (the long one) and the other is the intake gasket. Later model 258s did not have an exhaust manifold gasket from the factory, but many use one when re fitting the manifold. You would use them both.

I recommend you install studs. Two fastners (one at each end of the manifold) are already OEM studs. Studs do not need to be torqued into the head and if and when removing and reinstalling, the attachment holes aren't repeatedly screwed (so to speak).

JS
 

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