• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Joel's multipurpose XJ build (rocks/boulevard)

For safety, why not remove tires and lower the body on to the jack stands? I find it easier to lower the jeep a bit so I don't have to lift the tcase as high when reinstalling anyway.

I've done this a few times. Partially for safety, partially cause I don't have stands that are tall enough. Once you do it a couple of times, you get the steps down. Jack the axle, pull the wheels, place the stands under the frame rails, put tires under axle tube, lower jack.
 
Thanks for posting up fellas. These are the type of tips and tricks that I love.

When you jack by the axle are you putting the full weight in the center of the tube? I went side to side because I didn't like how much arc I put in the axle trying to pick it up in the middle.

Once I get this trussed it won't be an issue, but between now and then... FWIW when I blocked each tire I was lowering the tire onto the chocks so I at least had more preload that just kicking something in there.
 
I've always supported the axle with the jacks as close to the coil seats as possible for the reason you mentioned above. The rear axle I feel better about jacking from the middle since it's equal length tubes and it's not as heavy as the front.
 
Had my first venture out to King of the Hammers this past weekend. Transfer case behaved great running all over Johnson Valley. Bonus good news was that I finally found a way to get a decent night’s sleep in the back of the XJ.

I’d already built a storage area in the back so I no longer had a flat floor with the rear seat folded down. I ended up making a little bridge of 3/8” ply that bring that back to level and I supported it with a small chunk of 2x6 plus my rubber wheel chocks (http://www.harborfreight.com/solid-rubber-wheel-chock-69326.html) shaving about 3/16” off the top of each to give myself a better landing surface.

Had some foam lying around so I cut that up to make two layers. It’s about 2” of standard foam carved around the wheel wells and then 3” of memory foam on top of that. My daughter was so excited about sleeping in the Jeep that she ran inside and got PJs so she should try it out “properly”.

koth1.jpg



All I have to do is just fold this in half and it tucks behind the seat in the up position. The upside is that between the storage area and thickness of the mattress, I can put my pillow on top of the seat overhang and gain about 5” of leg room. That 5” is key as I can finally stretch out at 100% full length in the back (provided I’m aimed at a full diagonal that is).

Anyways, I was glad I did because the wind was blowing hard on Thursday night out in the desert so tent camping it would have been pretty miserable. Still taught my kid to make a fire, cooked marshmallows, went star gazing, and all in all, it made for some pretty special daddy-daughter time. I love that stuff. My kid’s such a trooper.

koth2.jpg


King of the Hammer’s itself was a pretty nutty experience. You don’t always realize how wide open it is out there and how much access you have to the spots. I need to look through the pics on my camera and see if anything’s worth posting. The above were just a few quicky cell phone shots. Just figured I’d write it up quickly while I had a lunch hour free.
 
I love getting my boys involved (4 boys, my poor wife!). If it's a camping trip they're always stoked. If it's just a day ride then it's hit and miss with their excitement level... but I drag 'em along anyway! That's quality time right there.
 
Can't vouch for all SYE kits but my rebuild kit had the correct bearing for the Advance Adaptors SYE.

This was the rebuild kit: http://www.ebay.com/itm/ws/eBayISAP...7913&item=330820387913&lgeo=1&vectorid=229466

Ebay listings will expire so for folks doing future searches the kit I was bought through seller "1416ecommerce" under the listing title "NP231 JEEP TRANSFER CASE REBUILD KIT FITS '94+ (WITH 16mm THICK INPUT BEARING)". It did have an extra bearing not needed for my setup that I assume is part of the stock slip yoke. It did not include the correct output seal as I already mentioned.
 
Joel,

An excellent thread -- thanks for sharing. I'm particularly interested in your exhaust setup, as mine is due for a stem-to-stern overhaul and I'm currently gathering ideas.

So if I understand it correctly, you're using the stock header with it's 2 inch collector and then expanding to 2.5 inches immediately following the junction between the header and the down pipe. Is that right?

Are you still satisfied with your setup? Anything you'd do differently?

Thanks in advance.
 
Raneil,

You're welcome and yes, my exhaust is presently header back from the stock header.

I do have a couple things: If you live somewhere with a bit more flexibility on smog I would do headers and an intake. This engine is such a dog in terms of hp/displacement that it needs all the help it can to breathe. I'm really curious what a decent set of heads and cam could do up top. If anyone has experience, I'd love to know what the bottom end can do reliably from an RPM perspective.

Off the shelf intakes look OK, but most of the headers are shorties and therefore doing almost nothing in terms of reflected wave pulse tuning. Since you want the torque down low you'll basically get the longest tube headers you can find. A stock 96+ XJ cam tuned for 5000 rpm peak wants something like 15" primaries and 15" secondaries. http://mez.co.uk/mezporting/exhaust_length.html. With a typical aftermarket cam it would be more like 17-18" primaries, 15" secondaries.

If you want to look into a DIY version to make something "proper" start here: http://www.kengineering.info/headers.html for an approachable guy who is mostly just sharing sound knowledge as an enthusiast.

I'm building custom headers for my RX7... Maybe someday on the Jeep.

In the meantime, the only other thing I'd consider is whether you ever intend to up the horsepower. I've been reading David Vizard's book "How to Build Horsepower" and he has a few really clever thoughts on exhaust flow and how you calculate diameters and the like. Specifically, he's the one who invented the rule of thumb that you need 2.2 CFM of flow per hp. I'd heard that before but never knew where it came from or how to apply it.

Answer: use the approximation that straight pipe flows 115 CFM per square inch of area. In my case that implies a 2.5" straight pipe is good for 564 CFM which in turn is good for about 256 flywheel hp before it would start to become a restriction. That says, I probably should have gone 3" if I was serious about a v8 in my future. But isn't that way too big for a stock 4.0L? Yes and no. First off, backpressure doesn't mean anything. I've read several very convincing arguments that the testing done in the 70s incorrectly correlated the presense of some backpressure with hp, with the real correlation was the effective pipe length (folks were seeing reflected wave scavenging and not realizing it).

When building an exhaust with an eye to performance: flow and pulse tuning is where it's at, period end of story. And actually, that's a pretty good way of thinking about what's going on. We have the flow of exhaust molecules and the pulse of the pressure shock wave as the exhaust valve first cracks open traveling at the speed of sound (speed of sound between exhaust open and valve overlap is what determines primary pipe length).

Related to the above Vizard recommends that you size the muffler according to flow not to diameter. For comparison your average perf core muffler (magnaflow or whatever) only flows about 60% of what a straight pipe would do. That means to match flow we should jump up a size at the muffler (IE 3" core for a 2.5" piping). When I figured that out it was like a light bulb going off. 99.9% of people who build exhausts--including the one I made for my XJ--do that wrong.

For comparison here's some muffler testing that exhibits what I mean. Rules of thumb are always ballpark but check the open straight pipe flow and you'll see Vizard is pretty close!

Muffler Flow Testing

All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM

Notable is the the core of the Dynomax Ultraflow is bigger than the inlets and outlets (Vizard designed it :rolleyes:). I assume the same is true of the Hooker max flow.

All of this I learned after building the Jeep exhaust but it just makes sense. FWIW Vizard's work is sometimes controversial, I know for a fact that his cam recommendations for LS engines aren't right. There was a huge discussion about "zero loss exhausts" on the rx7 swap board recently. It settles down and folks start talking tech about 50 or so post in. http://www.norotors.com/index.php?topic=13823.0

At the end of the day, I'm not sure I'd change my design even knowing the above simply because it packaged better as a 2.5" than a 3" might when I wanted to tuck it under my skid. I don't have data on what a spintech flows and it's enough different than the perf core stuff that I don't know whether it "should" be upsized or not. That's all hidesight though, and on net I remain very pleased. Still, the more you know the better you can make educated choices going forward.

-Joel
 
Last edited:
Wow... That's may be more answer than I bargained for -- thanks!

I'm content to leave the motor stock on this Jeep (got a little silly with the last one). With this exhaust overhaul, I'm looking to ensure that I don't go backwards at all on performance, but I'm not particularly looking to improve it much either. I just need to replace the rattling converter, the cracked header, and the old muffler. While I'm there, I figure I'll upgrade to 2.5" pipe all the way back.

I love the low profile of the Spin Tech muffler, so I'll probably go with that one, along with a basic 49-state universal converter (I'm in Texas).

I just hope my man at Big John's Muffler can keep it tucked up nice and tight like you did. I'm going to show him some of your pictures, just to put a little pressure on him. ;)

Speaking of which, your converter must be really close to touching the body, huh? Did you leave the factory heat shield in there (or did yours have one)?
 
At it's closest the muffler about a half inch clear but it varies between about a half inch and an inch because of the contours down there. Yes the factory heat sheild is still there. If a couple amateurs can build this in a driveway I have to assume a pro-shop with a lift would have no issues.

Floorboards get noticably warm to the touch but I've been driving it this way for quite some time with no ill effects.
 
Last edited:
Any other comments on the exhaust design theory? I'm coming from the go-fast world, but I thought Vizard's work was fascinating stuff.

For what it's worth, Vizard's kind of an old guy and claims to have more than a quarter million dyno pulls under his belt. He showed curves of a small block chevy making an extra 40 ft/lbs of torque across the midrange through the use of tuned length header design.
 
Fyi, I've tried to make a few forum suggestions and got really blown off by a few "members" the latest of whom basically told me to head for the cherokee forum instead.

http://www.naxja.org/forum/showthread.php?p=245884358#post245884358

Am I wasting my time here and/or does anyone care about a build thread done differently? About 2/3rds of folks on the forum aren't part of this here elitist "club". At the same time I don't see anyone else posting the math behind how to design parts on here.
 
you're not really supposed to weld 7075 though, it's no bueno. sure does machine well though. i use it for the bicycle parts i machine and sell since it wears much better than any other aluminum i've found.

ps, i was an engineer too so i'm fairly familiar with the properties of metals. manufacturing engineer though.


Nice build, not surprised you're an engineer (I'm a MET student)

As for the welding, here is a nice chart for selecting filler metals depending on the base metals. 7075 can be welded and retain most of its strength when using less common welding rods. The part will loose its heat treat though.

http://www.alcotec.com/us/en/support/upload/Alcotec-Filler-Selection-Chart.pdf

~Alex
 
FWIW, I'm subscribed and following pretty closely. If you decide to move the build thread, post a link - I've enjoyed it.

I don't think I'm going anywhere. It mostly just pissed me off that I was trying to be helpful and I've already spent quite a bit of time volunteering info only to have a few dudes talk $--t because they plunked down $ for a service that is typically free (with the acknowledgement that advertizing is the cost of free).

Nice build, not surprised you're an engineer (I'm a MET student)

As for the welding, here is a nice chart for selecting filler metals depending on the base metals. 7075 can be welded and retain most of its strength when using less common welding rods. The part will loose its heat treat though.

http://www.alcotec.com/us/en/support/upload/Alcotec-Filler-Selection-Chart.pdf

~Alex

Great link. Thank you. I just printed a copy. Do you have anything similar for steels (cast iron, stainless, etc)? I always dig on reference materials.
 
It mostly just pissed me off that I was trying to be helpful and I've already spent quite a bit of time volunteering info only to have a few dudes talk $--t because they plunked down $ for a service that is typically free (with the acknowledgement that advertizing is the cost of free).

You're personal view of this Club is irrelevant to your "Build Thread"

You are out of line, and you have absolutely no idea what you are talking about.
 
Oh come on man, you know you have plenty of people following this thread. And there are lots of philosophies about how to run a "club" but putting all that asside, have you been to jeepforum lately? Those ads on every single picture make me want to NEVER go back.

And in case you didn't know, you've got a serious problem: you're not normal pal, you're an engineer! :laugh3: I like your thread but even if I had the time & skill & money I wouldn't build a skid like that. It's just not my style or whatever. I'd rather just replace my $50 muffler if I loose in along the way. But I think your skid build was sweet and I'm glad you posted it - just different strokes for different folks right? (I work with engineers and got my MBA with a buch as well, you strike me as one of those "socially functional" engineers - you probably don't even think you have a problem! :D )

Anyway, I was at a rally recently regarding public lands and our right to use them and one of the speakers said something that resonated with me: We put thousands upon thousands of dollars into our rigs but then balk at paying $50 in dues. Well he was talking to me! Clubs like :NAXJA: spend time and money engaged in activities which keep MY trails open. So I just paid my membership fee - heck it's membership drive, maybe I'll win something. You should join up too and go on some club rides and meet-n-greets if you haven't. :NAXJA: seems to be about much more than just the forum...
 
You're personal view of this Club is irrelevant to your "Build Thread"

You are out of line, and you have absolutely no idea what you are talking about.

I prefer to be the one to decide what's relevant to my build thread. Given the frustrations with a few members today, I momentarily debated whether this thread should continue and that was worth some discussion here. A serious question as you look at the couple threads I was involved in today: Is this how you want to present your club? For instance, to the guy who suggested I should leave for suggesting I preferred a different structure and because I did so not knowing the bylaws... did you tell him he was out of line? You certainly didn't do so publicly, like you just did to me.

Oh come on man, you know you have plenty of people following this thread. And there are lots of philosophies about how to run a "club" but putting all that asside, have you been to jeepforum lately? Those ads on every single picture make me want to NEVER go back.

To the people following comment, to be honest I'm not sure sometimes. It seems like it gets some folks looking at it, but then I spend a full lunch hour writing up some of the most interesting vehicle design info I've ever run across (the exhaust post) and I mostly get crickets. Maybe engineers just thrive on discussion of ideas, but mostly I picture folks shaking their heads and going, "this guy's nuts..." That kind of makes me smile too, but you're right, even though I really dig wheeling, I dig building something interesting even more.

I haven't really looked at any other forums other than when stuff pops up in a google searches. I am still pretty new to the Jeep world. That said, I do have some Cherokee pride and for XJ's this seemed like the preferred place to be. There are some ridiculously awesome builds on here and some amazingly talented fabricators. There's also apparently a few folks who'll take a guy to task without a lot of provocation.

-Joel
 
Last edited:
Back
Top