Is this a header or manifold?

[UNCC_99XJ]

I actually have one of these coming to me today...just waiting on the FedEX man to make it appear at my door

 

[UNCC_99XJ]

Gotta say I do like it. Word of advice, spend a few bucks and get a good intake/exhaust manifold gasket from your favorite parts store. The one I picked up at work was somewhere in the neighborhood of $15-$20 and is a Felpro. The APN Manifolds come with one, but if I were to use the one they supplied me, I could see where there would be issues (has one section of it flaking off already, and it looks like it was partially bent in a couple places at one point in time).

 

[joe_peters]

Whatever exhaust manifold/header you buy, do yourself a favor and add in a stainless steel flex tube between the downpipe and the CAT to relieve stress--the cause of the manifold/header cracking in the first place.

 

[jeeperjohn]

Gotta say I do like it. Word of advice, spend a few bucks and get a good intake/exhaust manifold gasket from your favorite parts store. The one I picked up at work was somewhere in the neighborhood of $15-$20 and is a Felpro. The APN Manifolds come with one, but if I were to use the one they supplied me, I could see where there would be issues (has one section of it flaking off already, and it looks like it was partially bent in a couple places at one point in time).

I wish I could afford to get one of these and get it ceramic coated inside and out.

 

[mcbrado]

Hey again everyone; sounds like with a jeep the manifold vs header is a hard question; it's good to know I'm not alone in my bewilderment.

New question about things though:

In my readings here and elsewhere, people have said to install this with a flex-pipe or putting something between it and the engine block (?? I don't understand this well I don't think; if someone could explain please do)

Could any of you tell me what this entails? I was told by a mechanic that any manifold will risk cracking without the flex pipe. Is this true of the APN as well? How can I mitigate this? I have to do this repair this weekend and want to only have to ever do it once

Thanks again!

B

 

[joe_peters]

If you had really good engine mounts, and if you had a really good transmission mount, and if you never go out and flex your XJ offroad, then there was still a very good chance that the stock header was going to eventually break.

A stainless steel flex tube is CHEAP, and that will allow the engine and unibody to move in different directions without putting a strain on the header. Can the APN header survive without the flex pipe? Maybe. On ebay a 2.25" x 8" section can be had for $13--how much does the header cost? Cheap insurance in my book.

 

[5-90]

in my pea brain,

manifold:

header:

QFT.

That's pretty much how it breaks down - with the additional note (already stated) that "All headers are manifolds, but all manifolds are not headers."

Headers can be further subdivided into "equal-length" headers, "tuned" headers, and just plain "tubular" headers.

What we have underhood from the factory is a "tubular" header. It's not cast from a single piece (like, for instance, the well-known "Ram's Horn" manifold for SBChevvy with the centre dump.)

An "equal-length" header is just that - all of the primary tubes are the same length.

A "tuned" header has the length of the tubes (all the same) calculated to assist other cylinders in scavenging (by using the low-pressure volume in between exhaust pulses) at a given RPM or fairly narrow range of RPMs. Headers tuned for lower-RPM scavenging assistance are going to be longer. All "tuned" headers are also "equal-length" headers, but not all "equal-length" headers are "tuned" (an equal-length header can have a primary length randomly selected for no good reason. However, this is typically not the case - considering that equal-length tubes tend to require some creative folding to not have to cut them short...)

Similar principles apply to intake manifolds - with the exception that none of them are called "headers". However, an intake manifold can be tuned to assist with cylinder filling at a given RPM/RPM range (cf: "Helmholtz tuning,") but this is typically limited to higher RPM ranges, due to limited space underhood.

By now, you should be thoroughly confused!

 

[UNCC_99XJ]

I wish I could afford to get one of these and get it ceramic coated inside and out.

$149.61 shipped to my door...not a bad price if you ask me!

 

[winterbeater]

And there are also tubular intake manifolds for some vehicles! As long as it works, it doesn't matter what you call it.

 

[nochance9]

Similar principles apply to intake manifolds - with the exception that none of them are called "headers". However, an intake manifold can be tuned to assist with cylinder filling at a given RPM/RPM range (cf: "Helmholtz tuning,") but this is typically limited to higher RPM ranges, due to limited space underhood.

That's one of the better points in the 99+ intake right? And the all over larger plenum size?

Also, I've heard that wrapping your header can lead to premature failure? Would you guys agree with this statement? I've always wondered because i think it would be a good way to lower both under hood and intake temps.

 

[IslanderOffRoad]

This whole thread is basically a semantics argument.

 

[wolfpackjeeper]

This whole thread is basically a semantics argument.

thats what I said earlier...

 

[mcbrado]

Problem with the flex pipe idea

PROBLEM!

So I hear now that flex pipes will wear out before the manifold/header will and need replacing every 6-12 months and if I get a quality manifold/header to begin with. The muffler shops around town (all 4 that I called) said this was true about flex pipes, and that they didn't recommend to put any on it for me because of this, but the guy at the shop I am going to do the work at said I should have gotten a 70 dollar oem knock off with flex pipes and free shipping. Then again, everyone here says I should get this APN (which I did) and install flew pipes.

Who is correct? Any of you guys have long term experience with both flex and non-flex?

I assume adding a flex pipe involves welding, yes? I am not a welder. Some have said to install it at the end of this manifold, but the newer oem manifolds have two of them located at the left and right entrance tubes.

AH!

I am worried now that the APN may not have been the correct move. Is this thing really any stronger? Why?

B

 

[wolfpackjeeper]

the APN is a much better manifold than the oem knockoff with the flex section. It would be better to weld the flex tubing, but you could clamp it without any problems. It is gonna require that you cut a section out to fit it.

 

[5-90]

This whole thread is basically a semantics argument.

Ah, but "semantics" is the study of meaning. "Semantics" is what politicians use to screw us over all the time (try a semantic analysis of early American legal documents, vice those produced in the last 30-40 years.) "Semantics" is why lawyer's wives wear furry coats...

This is why mathematics is the only true "universal" language on the planet - mathematics has null semantic content, and therefore can't be mistranslated. Words can.

Another example - what's the difference between a "bolt" and a "screw?" I'll give you guys some time to hash it out before I tell you...

 

[Magus2727]

they are probably thinking of the cheap flex pipe that is used inplace of bent exhaust. you want a flex pipe. many vehicles come with these as stock and last much longer then 6 to 12 months. it is a small 4 to 8 inch length of special pipe with a stainless steel mesh on the out side. all 4 bangers that are front wheel drive have these. they allow for the exhaust to "pivot" in a location other then the manifold welds. the flex pipe looks like the junk OEM replacement manifold. the manifold only allows flex on only two pipes where the flex pipe on the exhaust after the manifold will allow the the whole system to move.

 

[5-90]

they are probably thinking of the cheap flex pipe that is used inplace of bent exhaust. you want a flex pipe. many vehicles come with these as stock and last much longer then 6 to 12 months. it is a small 4 to 8 inch length of special pipe with a stainless steel mesh on the out side. all 4 bangers that are front wheel drive have these. they allow for the exhaust to "pivot" in a location other then the manifold welds. the flex pipe looks like the junk OEM replacement manifold. the manifold only allows flex on only two pipes where the flex pipe on the exhaust after the manifold will allow the the whole system to move.

Precisely.

A planned part of the refit on my 88 is to have the first four inches or so of the downpipe replaced with a proper flexible section (akin to what you describe) to significantly reduce manifold cracking. Granted, I've also got 340Kmiles on the original manifold, but why take chances?

NB: Cracked exhaust manifolds/headers tend to be preceded slightly by failed/failing engine block mounts. Keep an eye on your mounts, and replace all three when one is failed/failing.

The mount may be easily checked using a 1/4" diameter knitting needle with the tip rounded over. Press the point against the rubber bloc, using your thumb on the opposite end. If the mount dents only slightly under pressure and fully recovers once pressure is removed, check it again in a year or so (or when you note vibration.) If there is a significant dent, the dent does not recover, or (Gawd forbid!) the point of the needle should penetrate; get a new set of mounts and replace them at your next opportunity.

If you have a significant oil leak that is draining onto the mounts, repair the leak then replace the mounts. Oil is antagonistic to the elastomers used in the engine mount cushions.

 

[mcbrado]

OK, so this APN is still good?

Can one of you send me a link to purchase the 'good' flex pipe and a link to the 'bad' flex pipe so I make sure and get the good stuff?

The guy at the repair shop said he has installed plenty of the cheaper replacement oem manifolds with the two flexes at the exhaust manifold intake pipes and never had a problem and had never heard of placing it at the 'beefy' (according to the APN specs haha) exit pipe at the end of a manifold. Is this a common thing to do and what are the specific directions I should tell the guy since none of the shops around here seem to know what I was talking about by doing it this way.

Have any of you run this APN for a few years or longer without/with 'good' flex pipe and willing to vouch for it either way; I am planning on doing this fix this weekend because it will probably be the last chance I get before I have to drive from Alabama to the UP in MI.

How long would this APN last with no flex pipe just bolted on the way it is supposed it says on its specs and do I really need a different gasket? If so, which one--my shopping choices at this point are AutoZone, Advance, and O'reilly I think since I need it so soon?

thanks guys,

B

BTW - Am also replacing my Tranny mount because my engine shifts a little forward and back, but I think the mounts are still good (hope I didn't jinx it).

 

[sjx40250]

Intake manifolds are just as challenging a design effort as headers. The length and cross section of the runners determine engine performance both at the low end and high end. The 4.0 intake manifolds are as long as they are to enhance the torque curve at low rpm. That is part of the reason you get 80% of torque off idle.

 

[5-90]

BTW - Am also replacing my Tranny mount because my engine shifts a little forward and back, but I think the mounts are still good (hope I didn't jinx it).

It don't matter. If one wants replacing, replace all three. All three mounts can be done easily in a couple of hours or so, and the most advanced tool you need is a floor jack with a bit of 2x6 to use as a load spreader under the engine oil sump.