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XJ Buildup III

What hood vents are those? Do they reduce underhood temps by any significant amount?

These louvers are made by GenRight and the do allow a lot of hot air to vent out of the engine compartment. I placed these louvers towards the front of the hood to enhance the airflow thru the radiator and out the hood.

Many will place their hood vents towards the rear of the hood, which is a high pressure area. At speed, the air movement at the cowl area of the hood impacts the windshield and creates turbulence and poor heat extraction. Example: https://www.youtube.com/watch?v=Pq2jLvwC9_8

I actually taped a couple dozen 3" long strings to the hood and observed the air movement over the hood before cutting the holes for these louvers.

Sorry, I don't have before and after temp measurements.

GenRight hood louvers https://genright.com/shop-by-vehicle/jeep-jku-4-dr-07-18/hood-louver-set-2pc-long-black/
 
These louvers are made by GenRight and the do allow a lot of hot air to vent out of the engine compartment. I placed these louvers towards the front of the hood to enhance the airflow thru the radiator and out the hood.

Many will place their hood vents towards the rear of the hood, which is a high pressure area. At speed, the air movement at the cowl area of the hood impacts the windshield and creates turbulence and poor heat extraction. Example: https://www.youtube.com/watch?v=Pq2jLvwC9_8

I actually taped a couple dozen 3" long strings to the hood and observed the air movement over the hood before cutting the holes for these louvers.

Sorry, I don't have before and after temp measurements.

GenRight hood louvers https://genright.com/shop-by-vehicle/jeep-jku-4-dr-07-18/hood-louver-set-2pc-long-black/

Do you get hot engine air entering the passenger compartment? Evos mitigate underhood temps in the same way you describe, and the temperature of the air flowing into the cabin of my Evo is definitely increased because of the hood vents.
 
UPDATE on the ZJ tank swap:

I took a trip to the San Juan Mountains of Colorado last month and was able to track my fuel consumption during this 1314 mile round-trip excursion.

Range with the modified ZJ fuel tank is 395 miles, averaging 15.3 MPG. Rig is set up with 4:88 gears, 295/75/16 tires, 4.0L/AW4, 6" lift, 4975 lbs loaded (4560 empty) traveling at 70mph ave @ 2850 rpm.

I know I'm quoting a fairly old post, but if you have an AW4 in your rig, I'm puzzled why you were going only 70 mph at 2850 rpm with this setup. According to my speed calculator, using 295/75-16 tires and 4.88 gears in locked 4th gear of an AW4, your speed should have been 77 mph. Even if I assume the tire was somewhat undersized, say 33" instead of 33.4", I still get 76 mph at 2850 rpm. And if I assume you meant a 265/75-16, I still get 73 mph. Did you measure by GPS or by speedo? If speedo, did you regear the speedo?
 
I know I'm quoting a fairly old post, but if you have an AW4 in your rig, I'm puzzled why you were going only 70 mph at 2850 rpm with this setup. According to my speed calculator, using 295/75-16 tires and 4.88 gears in locked 4th gear of an AW4, your speed should have been 77 mph. Even if I assume the tire was somewhat undersized, say 33" instead of 33.4", I still get 76 mph at 2850 rpm. And if I assume you meant a 265/75-16, I still get 73 mph. Did you measure by GPS or by speedo? If speedo, did you regear the speedo?

Nice catch.

I'll edit the post.
I am running a 295/75/16 BFG KO, which in their current state of 9/32nd tread depth, measure just over 32" at mounted tread center.

RPM in my post should have been 2750, not 2850, measured by my speedometer and yes, my speedo gear was replaced when I installed my axles with 4:88 gears, some 15yrs ago.

This shakes out to 71.5588 MPH, not 70MPH :doh:

MPH
71.5588
RPM
2750
True Tire Diameter
32"
Rear Gear Ratio
4.88:1
Trans Gear Ratio
.75:1
 
Nice catch.

I'll edit the post.
I am running a 295/75/16 BFG KO, which in their current state of 9/32nd tread depth, measure just over 32" at mounted tread center.

RPM in my post should have been 2750, not 2850, measured by my speedometer and yes, my speedo gear was replaced when I installed my axles with 4:88 gears, some 15yrs ago.

This shakes out to 71.5588 MPH, not 70MPH :doh:

MPH
71.5588
RPM
2750
True Tire Diameter
32"
Rear Gear Ratio
4.88:1
Trans Gear Ratio
.75:1

ok, your speed lines up with mine for your revised numbers. Doesn't the motor feel wound-out doing 72 mph at 2750 rpm? I'm getting ready to regear, and I was thinking of 4.10s for 31.5" tires because sustained 2700 rpm with this motor feels pretty busy to me.

BTW, you've done some very cool mods to your XJ. Are the unibody rails fully plated? Any cracks occurring in the usual suspect locations?
 
ok, your speed lines up with mine for your revised numbers. Doesn't the motor feel wound-out doing 72 mph at 2750 rpm? I'm getting ready to regear, and I was thinking of 4.10s for 31.5" tires because sustained 2700 rpm with this motor feels pretty busy to me.

BTW, you've done some very cool mods to your XJ. Are the unibody rails fully plated? Any cracks occurring in the usual suspect locations?

Wound up?

Cruising at 2700-ish RPM , the 4.0L is operating just below the peak output of it's power range.

https://www.automobile-catalog.com/curve/2001/1318895/jeep_cherokee_sport_4x2_2-door_4_0l.html#gsc.tab=0


Living at 4800ft elevation and frequently travel/recreate between 3500ft and 13,000ft elevation, I have zero regrets about running 4:88 gears.

I ran 4:56 gears with 31x10.50 and 32x11.50 tires on my 89 XJ for a few years and this combo performed well.

When it comes to regearing, there are so many variables that never appear on a chart and folks who solely follow a chart are more often disappointed with their gear choice.

Some of these unwritten variables include:

Altitude where you operate your rig (low elevation<sea level to 2,500ft> denser air=engine builds more power and can tolerate a taller gear. 3,000ft and above, as the air thins and HP decreases, your rig can benefit from lower gearing)

Automatic or 5speed manual. Some charts factor for this and the final OD ratio, but using a too tall gear ratio will leave your automatic transmission constantly hunting between 3rd gear and OD cruising. This also builds unwanted heat in the transmission/cooling system. This will also have a negative impact on fuel economy.

Added wind resistance due to lift and increased rolling resistance/contact patch from larger tires/wheels. Roof racks and light bars also increase drag.

Added weight of aftermarket bumpers, winch, armor, full size spare, trail recovery gear, tools, camping gear, bikes, etc.

Power loss due to aging engine

Pulling trailer/ATV's

All of these power robbers should be factored to your situation, which a chart will never be able to consider.

Yes, my unirails are plated nose to tail, this is one of the first mods that I did before I lifted my rig and I highly recommend it. Steering box area is plated on both sides, with welded sleeves in the unirail, so I've never once had a steering box bolt loosen/break. Zero cracking on the unirail in 15ys and 130k+ miles of use, the doors all fit tight still and the unibody doesn't pop and squeak like my non-plated 89 XJ did.
 
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Wound up?

Cruising at 2700-ish RPM , the 4.0L is operating just below the peak output of it's power range.

https://www.automobile-catalog.com/curve/2001/1318895/jeep_cherokee_sport_4x2_2-door_4_0l.html#gsc.tab=0


...

I guess I should say that the motor starts to feel a bit busy above 2500 rpm. Anyhow, as it turns out, stock 3.55 gears with 31" tires makes 3rd gear approximately the same overall gearing as 4.56 gears with 32" tires in 4th gear, so before I have my rig regeared, I'm going to do some more test drives in the 2700 rpm range in 3rd gear to see how things feel.
 
For what i do i really like 4.88s 5speed and 35" tires. Mostly town trail and highway driving where speed limit is 65mph and under. Shes is alittle busy at freeway speeds 80mph speed limit.

Sent from my SM-G781U using Tapatalk
 
Pics of how my rig currently looks

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:yelclap: Nice!!! Where was that?
 
:yelclap: Nice!!! Where was that?

The snow pics were taken in mid Dec '22 on our family ranch in Northern UT. There's about 5' of snow there now!

The bottom image what taken in Jan '23 at Sand Hollow Rec Area, near St George UT.
 
Looks like I got about 15 years out of this Flowmaster unit, which is a pretty good ROI.

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It's been rattling for a few months, but since I don't daily my Jeep, it wasn't a huge priority. I entertained the idea of a 40 Series Delta Flow 2 chamber, but settled on the proven 50 Series Delta Flow 3 chamber that has served me well for a decade and a half.
I welded a new unit in last week and it's nice to hear that "quiet" rumble again without all the rattles.

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I saw the thread where you are using that jiffy toe measurement tool. Do you make any attempt to measure thrust angle?

Nope.
Once toe-in is set, if my Jeep tracks straight and tire wear is even then I assume that my thrust angle is within tolerance.

If one is installing a new lift with adjustable UCA/LCA's, the first measurement to dial in is proper LCA length to set wheelbase, then adjust the track bar to center the axle.

Next, adjust UCA length to set caster angle and determine an acceptable balance of caster angle/front pinon angle to minimize driveline vibrations and return-to-center of steering. (Unless you have a CAD axle or manual hubs, then just focus on proper caster, as the driveline will not be spinning at freeways speeds and creating unwanted vibration due to mis-aligned pinion/t-case yoke angle.)

I'm running just under 6 degrees caster with 5.5" lift (I've rotated my knuckles to gain caster).

Then set proper toe-in, followed by adjusting the draglink to center steering wheel.

With a leaf sprung rear axle, there is little if any adjustment to be made to affect thrust angle, so if the front end is dialed in and the rig steers properly, tracks straight and tire wear is even, drive it.
 
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Thanks. I'm in the midst of doing a front driveline update on my XJ. There is about 1/16" difference between driver and passenger side distance between the front suspension radius arm mount point and rear leaf spring forward mount point on my XJ. I'll likely make the radius arm longer on one side to compensate, so just curious to see if you've had to deal with a similar situation.
 
Thanks. I'm in the midst of doing a front driveline update on my XJ. There is about 1/16" difference between driver and passenger side distance between the front suspension radius arm mount point and rear leaf spring forward mount point on my XJ. I'll likely make the radius arm longer on one side to compensate, so just curious to see if you've had to deal with a similar situation.

I have not, but sounds like you are on the right track to arrive at the perfect thrust angle for your setup.
 
My 4.6 stroker build has been in limbo for too long. Here are some details to get started and I'll share process pics as it comes together.

I'm using the Russ Pottenger/Bishop-Buehl Racing Engines recipe, consisting of:

• 99 4.0 Liter block bored .030 over.
• Scat 12 counter-weight 258/3.895 crankshaft
• Custom AutoTec 4032 high silicon aluminum alloy forged piston
• Custom forged steel Scat connecting rods with upgraded 927 Chevy wrist pins.
• Comp Cams 163-301-5 camshaft, which has been nitride treated for extra durability.
• Harland Sharp 1.6 roller rockers with tapered crown to fit under stock 4.0L valve cover.
• Rollmaster billet double roller timing set with custom cam bolt with built-in thrust button.
• 0630 casting Head, custom intake/exhaust porting and CCed chambers, fitted with premium Manley Performance stainless steel Chevy LS-1 valves 2.00 intake/1.55 exhaust with LS beehive springs/chromoly retainers.
• Ported 99 intake manifold with exhaust ports matched to Banks Revolver SS header and TB port opened to match 66mm throttle body.
• NRT Billet fuel rail, FluidFlow flex hose and 100psi pressure gauge
• NRT Billet 66mm throttle body
• 27Lb Bosch 4-hole injectors
• Balanced rotating assembly.


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Sounds like my BB build, what CR did he set it up for?
 
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