The end all Exhaust/ Header thread!

Warlock1 said:

Here's your APN manifold, even cheaper...


https://www.jeep-exhaust-manifold.com/

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Exact same link i posted... When you click on order it takes you to Ineedparts.com and says that it is no longer in stock

With all this talk about exhaust, I've not seen anyone talking about the down pipe/ B pipe / mid pipe.

Short of the junk Walker sells, I'm unable to find a nother option.

madmax said:

With all this talk about exhaust, I've not seen anyone talking about the down pipe/ B pipe / mid pipe.

Short of the junk Walker sells, I'm unable to find a nother option.

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Have one custom made.

Used to be that Borla made a great one. 2.5 mandrel bent. Hard to find one now.

Prodrives header comes with one.. Thats why I was looking there until I found a used one locally.. Still not sure what damn header to get now

techno1154 said:

What the FM rep told me made a lot of sense to me. The length and size of the 2.5" pipe allowed the gases to cool down significantly. This in turn allow the gases to get heavy which resulted in a reduced velocity at which it exit.

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This has been bugging me for some time, so I sent it to a close friend who's an engineer at aFe and at Gale Banks before that. It was a longer conversation, but it boiled down to the guy at FM was so full of shit his eyes are brown.


And that's proven by your fix, closing up just the last 18" - your exhaust does not move any faster until it reaches that point and will cool just as quickly.

Any real exhaust engineer will tell you back pressure is a myth. Keeping enough exhaust velocity to maintain scavenging is critical for sure, but going from 2.25 (factory) to 2.5 is not going to have any material effect.

cal said:

Have one custom made..

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I've done this in the past. More then likely end up doing this again

Likely rolling the dice on DNA, with new hardware and felpro gasket- hope it lasts long enough to check off the rest of the to-do list
Prefer to buy right buy once- need to pass emissions though and jeep funds need to be spread to other things atm.
Thorley will be on the wishlist

A guy on local Craigslist is selling one that looks like a DNA.

If your not welding anything you'd probably not like pace setter. Most seem to mod theirs to fit better, but they run well after.
I researched a lot of options before buying. I found cheapos cracked and expensive cracked. One might give some performance gain. I've gone cheap so I tried the other route, time will tell I guess.

Theres a lot of Apn looking clones I almost tried.

Hopefully you get what you pay for,but who knows.

Thanks for the heads up! I'll have to try and find the listing...

I think you're right- aside from super high dollar there isnt really a middle class. Banks through the $80 specials seem to be quite similar in designs, reviews, and longevity.


I dont think its like the ol' buying bumpers pick two of the 3 law:
Cheap, Strong, Light


Pree 99 seem to not have the fitment issues.. And then good motor mounts, a piece of flex pipe, and solid exhuast hangers the key to prevent crackage as long as possible

The cl ad is ot for 160+ tax? Double the price from amazon.. Damn

I'll only speak from the performance side but I've had my Banks Revolver on my 2000 for almost 2yrs. Knock on wood, but it hasn't had any failures yet, but I would either repair it or replace it because it's the best header for my motor.

cal said:

Have one custom made.

Used to be that Borla made a great one. 2.5 mandrel bent. Hard to find one now.

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That's what I did. The aluminum thing was something I tried to make the flange fitting better, Sorta worked but my main issues which I didn't realize until installing the band clamps is the header flange was bigger than the downpipe flange. Swapped to V band clamps last year and they work much better. I did make one of my own but it got regulated to the my trophy shelf of artwork.. :wierd:

cal said:

This has been bugging me for some time, so I sent it to a close friend who's an engineer at aFe and at Gale Banks before that. It was a longer conversation, but it boiled down to the guy at FM was so full of shit his eyes are brown.


And that's proven by your fix, closing up just the last 18" - your exhaust does not move any faster until it reaches that point and will cool just as quickly.

Any real exhaust engineer will tell you back pressure is a myth. Keeping enough exhaust velocity to maintain scavenging is critical for sure, but going from 2.25 (factory) to 2.5 is not going to have any material effect.

Click to expand...

Well yes I would have agreed with this but I have noticed a change from only changing the exhaust tubing size. I ran 2.5” the first time I redid my exhaust and it seemed to be slow to respond to throttle input and just doggy overall. I changed the down pipe and everything to the back axle to 2.25” and left the 2.5” running from the glass pack to the tail pipe 2.5”. Made a noticeable difference in the engine response.

I don’t recall changing anything else at that time and I can’t say why it would have made a change. But tthat was the days of alot of late nights :confused1:dunno:

I also remember a video where one of the shops got a nice pair of headers and dented them with a hammer while pulling dyno runs to see what power they would lose, they lost around 1 hp.

So I don’t put much into exhaust anymore other than keeping it from cracking or getting smashed.

I'm on my 3rd stock-style manifold with bellows on either end. Brown Dog motor mounts (poly filling shakers) and all hangers are in place and "tight". Not sure how you completely eliminate up/down movement without solid mounts though.

ShoeterMcgav said:

While the gains in flow would be minimal with just a header vs the stock piece- its not my primary concern. Only way exhuast will be the limitimg factor is if more air is coming in. With out porting or head or stroking or forced air... Im sure its a slight if any increase to power with a true header.

Running one with 3 inch exhuast all the way back for instance wont just magically give the engine more power. Imonthe stock exhuast is better flowing then most cars. Id agree a cai with header would be an upgrade to stock- but nothing over 15--20hp max

Mine is cracked. So it needs replacement. Bang for buck is primary concern for me.

Ebay header or protuning lab is where im leaning

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Exhaust scavenging will definitely make the engine more efficient, even if the same amount of air coming in is maintained. Most of us will see a low-end torque increase from these headers as the primaries are considerably longer than stock.

Headers are about tuning exhaust pulses to match the engine's expected operating RPM and cam profile. Your engine breathes in pulses, not a continuous stream like a garden hose. If you design a header correctly, with the primary tubes arranged to follow firing order, the exhaust pulses will leave a low pressure wake behind them that helps pull the exhaust out of the next cylinder. Changing runner length and diameter will change the optimal RPM this occurs at.

Short and simple of that by looking at pictures is longer tubes means more low-end power, and shorter ones mean more high-end power.

The stock manifold, while better than a cast iron log, has room for improvement, as it minimally enhances scavenging, and there's definitely no way a stock 4.0 would see the RPM necessary to really see any improvement in breathing with the stock primaries.

I think you said it- solid mounts, might be best?

I currently have the "updated" one with billows that are supposed to prevent cracking too... And well it didnt lol

Adding in the flex piece to absorb the brunt of the bouncing might be your best bet? A solid hanger or 2 wouldnt hurt either. Even if the flex piece fails- easier to replace then tearing out the mani/header.

Why are you om your THIRD manifold??? Your post seems to agree with the idea of improving upon that design? Albiet minimal without adding more air in... But nevertheless... And cheaper in most cases.

Are you looking to go that route now? Which one are you thinking if so?

ShoeterMcgav said:

I think you said it- solid mounts, might be best?

Third manifold? I currently have the "updated" one with billows thats supposed to prevent cracking too... And well it didnt lol

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Yep. Just saves #1 and 6 from cracking. All the other primaries were cracked where they meet the "secondary".

ShoeterMcgav said:

Adding in the flex piece to let the brunt of the bouncing to absorb might be your best bet? A solid hanger or 2 wouldnt hurt too. Even if the flex piece fails- easier to replace then tearing out the mani/header

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Ugh. Well, running solid mounts anyway. How much worse could it get anyway?

ShoeterMcgav said:

Why are you om your THIRD manifold??? Your post seems to agree with the idea of inproving upon that design? Albiet minimal without adding more air in...

Are you looking to go that route now?

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Lifetime warranty from O'Reilly on the Dorman jobber. First one I bought from Rockauto.com and was a PITA to deal with. Bought the next from O'Reilly for $50-ish more, but can just exchange in store. When I start hearing the "chuff-chuff-chuff", I call in to order another, head home and remove the old one, head down to exchange and stuff the new one in. Pretty good at it now, only takes me a couple of hours including transit to/from the store.

I'm going to add one of these as I question the flex joint's ability to survive much in the way of rock contact:

Fair enough..

The flex joints are plenty strong imo. Ive seen them dented and not leak- plus on the xj the wiremesh would be tucked away from most rocks- Id think a blow thatd damage it would also cause the same damge to the pipe if it wasn't there?

My subaru had that style of bolting up at the mid pipe.. It might alleviate some vibes, but I dont think it'd help much in the way of movement. Could be dead wrong, but it has to be tightened enough to not leak, then it acts just like its bolted regularly. Definitely not saying it will do nothing, just don't know that it'd have the desired effects.

Originally Posted by cal
This has been bugging me for some time, so I sent it to a close friend who's an engineer at aFe and at Gale Banks before that. It was a longer conversation, but it boiled down to the guy at FM was so full of shit his eyes are brown.


And that's proven by your fix, closing up just the last 18" - your exhaust does not move any faster until it reaches that point and will cool just as quickly.

Any real exhaust engineer will tell you back pressure is a myth. Keeping enough exhaust velocity to maintain scavenging is critical for sure, but going from 2.25 (factory) to 2.5 is not going to have any material effect.

Click to expand...

Weasel said:

Well yes I would have agreed with this but I have noticed a change from only changing the exhaust tubing size. I ran 2.5” the first time I redid my exhaust and it seemed to be slow to respond to throttle input and just doggy overall. I changed the down pipe and everything to the back axle to 2.25” and left the 2.5” running from the glass pack to the tail pipe 2.5”. Made a noticeable difference in the engine response.

I don’t recall changing anything else at that time and I can’t say why it would have made a change. But tthat was the days of alot of late nights :confused1:dunno:

I also remember a video where one of the shops got a nice pair of headers and dented them with a hammer while pulling dyno runs to see what power they would lose, they lost around 1 hp.

So I don’t put much into exhaust anymore other than keeping it from cracking or getting smashed.

Click to expand...

Stumbled upon this thread and it interests me as I'm making changes to my system and have some similar questions regarding pipe diameter.

Years ago I switched my exhaust to 2.5" pipes all the way back and running a Summit glasspack (all I could fit with the 4-link). Its seemed okay power wise (wasn't really expecting any noticeable gain) but the drone at 2,000-ish rpms is super annoying on the trail with the doors off.

Thinking about returning to 2.25" pipes and I'll be switching to a chambered muffler (I prefer quieter as opposed to loud, as long as it doesn't kill performance/power). I'm hoping this will get rid off the droning sound and the smaller diameter pipes should be a heck of alot easier to fit.

I will not be running a downstream cat (I still have the two pre-cats - its a 2000.)

Is there any downside to choking it down from 2.5" to 2.25" somewhere on the downpipe (after the header, and likely after the two turns)?

Bought a Borla SS all the way back and still running it. It had a 100,000 mile warranty, which now is expired! Sounds the same as when installed.
Combined with high flow cat and replacement injectors, I did see an improvement in mileage and low end. Barely noticeable, you have to be one with the Jeep!

Just to add, the stock TB is restrictive. I bored out one to straight through or 60mm. It improved steep grade climbs on the highway. It did 'upgrade' to a 62 BBK. I didn't notice much if any improvement. I do have the 99+ intake and a 2.5 exhaust. Also a Dough Thorley header. Some noticeable gains. Also, tried 4 hole injectors and 12 hole injectors. No noticeable gains. 4 hole ran smoother. the 12 holes seemed to gain power initially. But I think other issues caused problems. Changed spark plugs to NGK and the engine ran better.
One thing I plan to try is an adjustable Fuel Pressure. Note BajaBronco's Stroker thread and Jordan88 on Mall Crawler.

My 90 has the renix TB so not bored out. It does have Five O bosche (green) injectors (4 Hole?) modified MAP voltage and Really old multi ground spark plugs. Only way I could pass inspection was with the MAP adjustment and the plugs.