The end all Exhaust/ Header thread!

So im going to have to do this to soon.

First question are all flanges the same thickness. Meaning I could bolt 91+ headers on my 89. Ill put o2 sensors where needed.

What is best. I see lots of stuff on ebay that looks similar to the revolver rcp is working on. Im undecided on pretty much anything Gayle banks has to do with, marketing.
Doesn't mean that's bad but often more is put into making the sale than making a quality product I also in a short search see a few banks 4.0 headers cracking wich leads me to believe that they are similar to all. Rcp also seems to have done repairs.
From my experience a cracked 4.0 header is doomed ounce cracked unless it stays parked. I also know rcp is a very experienced welder and may get the cracking locked down where I apparently can't.

On ebay there are headers with two collectors I think a banks copy aswell or banks and China both copied the design. These almost appear to be close to equal length primary tubes.

I'll need to do some research on if actual 4.0 equal headers exist.

I have a HO header on hand that has two flex joints in it. Its more a manifold than a header.

Im curios to see if rcp actually gets 20mpg. If so that style may be a good design wether a cheap ebay or revolver

Im not concerned much about power or mpg im more concerned that my jeep sounds like crap due to cracks and a pretty much pretzled exhaust system.

Though if gains could be like 20 horse maybe it would be worth it over a HO though all gains are always like at 12000 rpm and not much of any down at 2000-2500 where I like to run the rpms.


Ok HO header it is i think talked myself into it.

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The main difference between the 87-90 Renix header and the 91+ HO is the EGR bung. I do have an '88 Comanche. I used a Pace Setter header on it. Then replaced it with a Clifford. The Pace Setter was sold and used by someone else. The Armor Coat (ceramic coating) looked good after two years.
I went with Doug Thorley at the time for my '98 XJ. Mainly I was looking for a ceramic coated header. It is suppose to be a copy of the Mike Leach design that MOPAR sold. I was interested in the Banks at the time. The reports of cracking did influence me. I think they have redesign it a few times. I will say, I think my Doug Thorley has cracked. It did have an on going battle with Death Wobble and it took out my motor mounts.

Thank you 75 for the response. Glad to see it will bolt on with much trouble

Between this thread and rcp I was left thinking well????? Was this all talk and no info or decision.

Mostly because it appears anything bolted to the 4.0 exhaust ports will crack and gains are so marginal that its hard for most to tell these motors aren't doing many dyno runs

So everyone is buying based on limited info along with gut feelings and sometimes sharing these opinions and gut feelings with others

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Its hard to judge, as you are brining up. Another aspect though is, what is the rest of the system capable of? Take the 99+ Intake Manifold. For years the discussion was it might add 5-8 hp. Not much in the way of Dyno runs etc. Then some documented say 12-16 hp increase, just by changing that. Some of it comes down to, what is the exhaust pipe diameter, is the TB bored, stroker, head modified. etc. ?
I think Dino's 4.0L page gave some incite early on. In my case on a '98 XJ, I had the 2.5" exhaust, Thorley header, stock head, KOLAK ignition and probably on 31's with 4.10 gears. I was still having issues with some graded on I-78 in WV. I think I was on the original trans. No real issues with it, just leaking some. So, I bored the TB to 60mm. I didn't have issues with those grades.
I did change some stuff, rebuilt trans and then 32.5's. I still didn't have issues with those grades. Still, some issues with shifting and I think I need about 4.30 gearing.
Also, the stock 87-99 header is probably not that bad. I will be changing on a 2000 from the cast iron manifolds to a JBA header. Possibly this weekend. I will note I think I have an exhaust leak. So, not an exact or perfect comparison. I'll also change the O2 sensors.
As stated before, I ran the Pace Setter Header for about 2-3 years. No issues. I was getting a corrected 23 mpg with the manual BA/10-5. By the OD it was 25 mpg. I think previous owner change the rear end from a 3.07 to a 3.55.

This is what I have to work with. I dont think spending 100-300 to buy something that might crack is a smart investment.

I'll get a muffler maybe a spintech or fte twister put as far forward as I can put it to kill sound.
Run new 2.5" pipe and dump it over the axle

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I'd include a Magnaflow Cat, and to remove the dent in the down pipe. Those bellows are on some high end diesel motors. Also, I see some put a flex joint in the middle of the down pipe. My 2000 has a bracket on the passenger or right side of the trans, that support the down pipe there. I tired to look for another online. I don't know if it is factory or aftermarket. I do see some shown for possibly the ZJ or WJ.

Edit: Evan, in one of your post you said you were running 3" exhaust. ?? On Frijolee post I ordered some of Vizard's books. In the exhaust chapter it 'recommended' to use larger pipe in bend areas. As some point I might try it. Probably my next build. Also, I bought the head porting book. Interesting stuff. I did a 4.0L years ago, with Elgin Chevy valves. Haven't run it yet. I came up with a bit better solution to run aftermarket 4.0L springs. I had to turn down the retainers last time. The stock springs were ID .830. The Sealed Powers are ID .865. I found some Manley retainers to work. Also, I want to try either a 37 degree or 30 degree intake valve seat. Suppose to be better for lower RMP motors.

What exhaust manifold is that?

Stock one thats not cracked yet
HO I think but not 100% sure

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So the earlier stock exhaust manifold is welded tubular and not cast? My 2000 exhaust manifold is definitely cast.

maxbraketorque said:

So the earlier stock exhaust manifold is welded tubular and not cast? My 2000 exhaust manifold is definitely cast.

Click to expand...

Yes, the 2000-06 is a cast iron manifold. The 87-99 is a tubular steel header. I think there is some difference between the 87-90 RENIX and 91-99 HO. I think the 87-90 sits a bit lower. Aftermarket headers have a bit bigger primary tubes, to they fit both.

Interesting. The lack of significant rust on the tubing suggests that it may even be a 300-series stainless steel, but I would tend to believe that its 400-series. Inclusion of expansion bellows is impressive too.

I bought a xj for parts. This header was in the back with an intake and set of pistons.


Yes im running 3" i didn't see any gain over the stock exhaust i took off.

I've orderd a spintech 2.5" 6000 muffler. Pretty sure I can place it in front of the transmission crossmember.
I'll run 2.5" from header and probly dump just over the axle.
The last xj exhaust i did i ran 2.5 to the bumper used a 14" magnaflow on that one. To me it sounds like crap and this also didn't seem to make any gains or make it worse.
I may actually see a improvement my current exhaust is dang near closed off below the oil pan ,its been drug in the rocks alot. The oil pan is dented from the exhaust hitting it.

I like playing with exhaust not sure ive seen gains on any vehicles that are measurable on the but dyno.

I did reduce egts on my cummins going to 5" from 4

Rambling

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I've seen that general assessment by others here and in discussions elsewhere on the value of exhaust mods on an otherwise stock 4L motor. Kinda too bad because exhaust mods are relatively easy.

I think it would be cool to stick a carbide burr in and port port match both the intake and exhaust manifold to the head maybe the head to the gasket then see what the but dyno says.

To save time over doing all pie cut bends I ordered a diy exhaust set on ebay. Has 4 each 45deg 90deg and 4 U bends. This well save alot of time for me fabbing from header to the rear axle.

I almost went with 2.25 size due to front driveline clearance but decided 2.5 ill have extra bends for other exhaust and 2.5 is more common coming off v-8s to fabb crossover pipes

Typing this ive likely talked myself out of grinding anything. Probly just not worth it.

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maxbraketorque said:

I've seen that general assessment by others here and in discussions elsewhere on the value of exhaust mods on an otherwise stock 4L motor. Kinda too bad because exhaust mods are relatively easy.

Click to expand...

Percentage of gain is always based on what you started with, in my case (and I usually forget to mention) that besides a stroker with a ported/ polished head I also have LS1 big valves!

Definitely gains for your setup. No way would I consider stock size exhaust for your motor.

Started the swap today.

Started holding bends up to envision downpipe

Probably going to have to make my own bends. The bends in the kit are to long.

Orderd a gasket cause no local stores had one.

Gong to be more a project that I thought

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Who made that old exhaust manifold? Your stock replacement is 10x better.

Assuming its stock by chrysler or whoever they farmed it out to.

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Wow. What a POS.