[UltimatE]

So im going to be boring out my TB next weekend, and getting a cone air filter for my 4.0.

In order to let it breath a little more, im also looking into headers.

http://www.autopn.com/store/pc/viewp...dProduct=20009

This part is listed as a manifold for the 4.0. What is the difference between a header and a manifold? Does that 'manifold' in the link flow any more than the stock one?

[spitfirees20]

Headers flow a tad bit more mainly because of their lenght, but that's a well designed exhaust manifold so it would be close. I've heard on the 4.0 it's not that much of a gain over the stock exhaust manifold. I have the stock manifold wrapped in header wrap, flows great and works fine for me.

[UltimatE]

Originally Posted by spitfirees20

Headers flow a tad bit more mainly because of their lenght, but that's a well designed exhaust manifold so it would be close. I've heard on the 4.0 it's not that much of a gain over the stock exhaust manifold. I have the stock manifold wrapped in header wrap, flows great and works fine for me.

Do you have any engine/exhaust mods? like bored tb, high flow cat/muffler, or cone filter?

[spitfirees20]

Originally Posted by Ultimate157

Do you have any engine/exhaust mods? like bored tb, high flow cat/muffler, or cone filter?

http://www.jeepforum.com/forum/f180/street-jeep-buildup-276034/

All of the above and plenty more.

[UltimatE]

Originally Posted by spitfirees20

http://www.jeepforum.com/forum/showthread.php?t=276034

All of the above and plenty more.

Haha, didnt realize who you were thanks for the info

[XJ4oh]

4.0's come stock with a header. Thats why there isnt a huge gain in stepping up to a performance header. You can improve with a good header and new downpipe from what I hear.

[dogwonk]

Originally Posted by XJ4oh

4.0's come stock with a header.

Huh? No they didn't. What cam stock is a manifold, not even close to being a header...

[XJ4oh]

Nevermind, its late and im not thinking right.

[CANiHaveGasCash]

I thought they were different names for the same part. They serve the same purpose and are installed in the same location. Exhaust manifold is usually in reference to the stock peice and header is usually the term for the aftermarket peices that will flow more.

[dogwonk]

A header has equal length tubes that flow into a collector, a manifold has neither of these.

As you can see...

Stock:



Header:



Notice the equal length tubes and collectors at the ends on the header. The stock one dosn't have either of these features.

EDIT: For some reason pics didn't show up, they are links. Sorry about that, not sure why that was the case.

[CANiHaveGasCash]

Originally Posted by dogwonk

A header has equal length tubes that flow into a collector, a manifold has neither of these.

As you can see...

Stock:



Header:



Notice the equal length tubes and collectors at the ends on the header. The stock one dosn't have either of these features.

EDIT: For some reason pics didn't show up, they are links. Sorry about that, not sure why that was the case.

There are equal and unequal length headers therefore your definition is incorrect.

[Matt Gertsch]

I replaced the cracked, stock mani with a Gibson stainless. I noticed a nice gain in power. The stock manifold isn't designed to flow or to time exhaust pulses. The pulse timing is what is important in header design. If you're looking for gains, I'd get a Banks or Gibson. Basically, buy something that is marketed as a "header".

[CF]

I've always thought the diference was that exhaust manifolds were a cast piece, and the tubular pieces were headers (whether stock or not).

[-XJguy-]

If I am not mistaken a header IS technically an exhaust manifold, the correct nomenclature is: performance tuned equal length tubular exhaust manifold, whereas the factory item is simply a tubular exhaust manifold. Are they both headers...well depends on who you ask. 'Header' used to be reserved for tubular exhaust manifolds which were only found on high end exotics, tuners, etc., but since most modern cars now come with some sort of tubular ex. manifold, as opposed to the old heavy cast iron units, often people refer to any aftermarket exhaust manifold as a header whether it be of equal length or not.

XJguy

[Matt Gertsch]

Originally Posted by -XJguy-

If I am not mistaken a header IS technically an exhaust manifold, the correct nomenclature is: performance tuned equal length tubular exhaust manifold

They don't need to have equal length primaries. Show me an equal length header for a 4.0. They're rare, because they would mis-time the exhaust pulses. You need to have unequal primaries in order to properly sync the pulses for maximum scavenging.