Q&A for Jeep XJ Cherokee and MJ Comanche: Engine Upgrades & Swaps
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Sent: Saturday, September 29, 2012 3:49 AM
To: 4WD Mechanix Magazine
Subject: Griffen radiator for XJ Cherokee
Hi, I just
watched your video on the new radiator install on the Cherokee XJ. Can you tell me where I can get one of these
from as I can't seem to find anywhere online.
radiator I installed is a prototype for a new design offered by Griffin. I have heartily encouraged
production of this unit, it's a great fit and success story for cooling. Every word shared in the videos is
accurate and further reinforced by my evaluation and testing over a long, hot summer at northern
includes A/C running continuously with ambient temps above 100-degrees F, high desert country trail running,
stop-and-go traffic at Reno and heat cycling from startup to squelching heat soaks after shutdown before
restarts. Restart after brief (2 minutes or so) fan run-on is at 185-degrees F every time—as noted in the
temperature of this cooling system is at thermostat setting, with a peak rise of five degrees F under the most
strenuous tests. The twin Spal fans are very impressive, bringing temp down to thermostat set point
immediately, regardless of driving conditions! These fans, set to run after engine shutoff, will bring the
radiator temperature to 185-degrees F in just over two minutes, even when ambient temperature is 105-degrees F, and
the vehicle is parked in the sun.
advanced engineering of the radiator unit, Griffin has creatively mated the Spal twin electric fan and shroud
system. Ancillary benefits include a bump in fuel efficiency and noticeably more engine power. Griffin
has built a state-of-the-art, proprietary radiator and fan system here.
I will contact
Griffin Radiator this week and see where the production/marketing stands with this XJ Cherokee radiator and fan
system. Expect an update, Aaron!
East Cherokee 4.0L Ready for V-8 Swap or Stroker Build-up!
From: Ibrahim, Saudi Arabia Cherokee owner
Sent: Saturday, July 14, 2012 3:00 AM
To: 4WD Mechanix Magazine
Subject: For 2000 Jeep Chroki
Hello, my name is
Ibrahim from Saudi Arabia
a [Chroki] Sport model 2000 Gulf. Searched a lot and tired search.
We do not have
[Cherokee] experts in Saudi Arabia. I am a fan of speed and high
performance. One person said to me that
the engine should be replaced with LS1 V-8 to enjoy high-performance.
to avoid cost, can
you equip [Chroki] engine 6 cylinder stroker with a computer to
re-programming, and how much it cost? Is
there a difference high-performance, and how much HP will I get it?
Second, you could add a turbo engine [Cruki] without any additions?
you can install the engine Ford Mustang [Cruki]? Where you think that the cost will be
apologize if my style is not good writing, I do not speak enough English.
Ibrahim, pleased to receive your questions…You are asking about the Cherokee 4.0L inline six-cylinder engine and
stroker rebuild. I believe this is the best and simplest way to gain performance from an XJ Cherokee
Jeep. At the magazine website, you will find a series of HD videos, including an interview with Tony Hewes
at Hewes Performance Machine, Reno, Nevada, USA. Tony builds the 4.6L Jeep stroker six-cylinder
engine. I agree with his methods and choice of parts.
links to the HD videos at the magazine site. On the sub-pages to this link, you will find six additional
videos plus more videos on tuning the 4.6L six:
should help clarify the 4.6L stroker inline six build for the Cherokee engine. Although supercharging is
available for the 4.0L engine, the stroker crankshaft provides dramatic gains—with or without
From: Ibrahim at Saudi Arabia
Saturday, July 14, 2012 11:36 PM
To: 4WD Mechanix
Subject: RE: For 2000 Jeep Chroki Saudi
Thank you for your response to the topic. Yes I mean 4.0L engine. The modified engine results will be strong or replace
it with another engine? Often we have been installing V-8 LS1 engine or turbo
2Ji. What do you think Mustang
engine for installation in
[Cruki]? For a system
re-programming the computer one person advised me to install the
EMS computer will get better results if inserted at the left engine
case. What would you recommend?
the stroker 4.6L Jeep inline six will produce 230-300 horsepower, depending upon the compression ratio, camshaft
choice and other modifications. If you want maximum dependability, the 230-250 horsepower build (Tony Hewes'
versions) make the best sense.
I do like the Chevrolet LS1 and also the Mustang 5.0L and 4.6L V-8s. These are options but require adapters,
fabrication work and a suitable transmission. There is much construction work involved, and you either need a
well-equipped shop or a budget to sublet this work to a suitable shop.
The Mustang 302 (5.0L) HO pushrod V-8 is a proven, reliable design. There are adapters and transmission
alternatives for this swap or the G.M. LS1 V-8. (Visit www.advanceadapters.com, an advertiser at the
You could expect 240-300 horsepower from a stock or lightly modified 302
Ford H.O./MPI V-8, depending upon compression ratio and camshaft, valvetrain and other modifications. The LS1
offers more horsepower in stock form…There would be a custom cooling system required, and you live at Saudi
Arabia, so engine cooling is an issue.
Given the amount of work involved, the 250-300 horsepower from a 4.6L inline six Jeep stroker engine would be the
easiest and least involved way to achieve your goals for the Cherokee.
You can have a stroker Jeep six motor
built at Saudi Arabia by a qualified automotive machine shop. U.S. cost ranges from $3000-$5000 for a thorough
rebuild and the necessary modifications. A shop can review my magazine
articles and HD video series for ideas on how to build the engine.
cooling system and fuel injectors do need attention. The PCM (original Cherokee computer) will work with the
stroker six build-up. Many change the fuel injectors to 302 Ford V-8 type at 24 lb. rating. I am researching a
specific part number that achieves the desired results.
are replacement injectors and other information available at the HESCO
website: http://www.hesco.us/shop.asp?action=cat&catID=7550. Visit the HESCO Jeep website and see the additional information on the
stroker 4.5L to 4.7L inline sixes. HESCO also offers its own aluminum cylinder head for those who want maximum
performance. They sell the many parts used in the stroker six build. HESCO also has dynamometer results for
various stroker engine builds.
Performance Machine at Reno, Nevada can build a complete stroker 4.6L like you find at my magazine. You can
reach Tony Hewes by Email or phone. My magazine articles include the Hewes Performance Email address and phone
should help clarify the cost of building a stroker six. Also see my latest tech coverage of the Griffin Radiator for the
Cherokee. That radiator would work well with a stroker six. This new design Griffin Radiator
will be available soon.
Moses Airing XJ Cherokee Cooling Issues
I shared comments with my friend Jim, an XJ Cherokee owner and former aircraft engineer. The following
E-mail exchange ensued. I will continue to address cooling system issues on the 4.0L and other Jeep
Moses: Jim, I had a burst of
inspiration today while wheelin’ with a group out of Gardnerville, shooting some graphics for the June issue. The
XJ engine, despite the mild April temperature and use of lower range gearing, hovered around 210-degrees F on the
temp gauge. I began connecting what the terrain demanded with the engine temp…the automatic transmission [AW-4] is
clearly involved. I’m now curious whether owners with manual transmissions have this temperature sensitivity issue.
Regardless, the XJ is a fine candidate for a transmission cooler! A synthetic ATF, if specified for use in this
unit, would not be a bad idea, either. 100% synthetic ATF can drop trans temp as much as 50-degrees
Jim: I have been using 100%
synthetic ATF in the AW-4 since day one. I’m a believer. I use the Amsoil Universal ATF but there are others out
there, including a Mobil 1 version. I think they really do help. They do run cooler—they lubricate better so things
don’t get as hot and they have a higher heat transfer rate than standard ATF, so they give up more heat when they
go through the radiator and transmission cooler. If things do heat up a bit, they can run a lot hotter than
standard ATF without breaking down…That’s three good reasons to run synthetic ATF. I’m curious about the cooler—my
XJ came standard with an auxiliary cooler sitting right in front of the radiator and clearly visible behind the
grille. You don’t have one? Must be part of the tow package.
Moses: My XJ does not have
the cooler. However, I’ve worked with automatic transmissions and coolers since 1969. In my view, a cooler in front
of the radiator is a liability. I always mount the cooler behind the radiator. Although the air passing through it
is hotter (preheated from the radiator, essentially), this is still better than mounting the cooler (which is much
hotter than the radiator coolant) in front of the radiator. In front, the hot air heats a section of the radiator
core. On an XJ, that’s a liability…Just running auxiliary lights in front of the grille was enough to overheat the
engine in the summer! Imagine blocking the core with a “heat cell” like a transmission cooler. Bad enough the air
conditioning condenser is out there…So, what I will do is mount an auxiliary (cooler fin-to-air) cooler behind the
radiator, definitely in the air stream, not necessarily in the fan flow stream unless I can find a low pressure
zone that is not flowing hot air from the radiator core. The aim is to keep heat-saturated air from the radiator
core from passing over the transmission cooler. The downside to this approach is that the trans cooler’s air supply
is likely more static and reliant on ambient air or road speed air/draft for cooling…On that note, I might build an
air draft fin to create a low pressure zone behind the auxiliary cooler to draw air over the cooler—this would at
least work with the vehicle in motion…
Jim: Several cooling system
upgrades have helped my XJ. These have included an improved flow thermostat housing and a water pump with improved
impeller design. If you want to go that far, there are aftermarket radiator options as
Moses: I’ll do a
comprehensive test before sharing information in the form of magazine articles. These ideas all make sense. The
best approach is to systematically make individual changes and measure the gains, if any, from each…Thanks,
Considering your comments on a diesel swap of the VM 2.8L (J8 engine)
into the XJ Cherokee, I think this would be a brilliant idea! I have considered this swap for a while now. A Mopar
diesel engine is a more attractive idea than finding another random diesel. If you end up doing this, would you
provide general cost break-downs and the suppliers you use?
Matt, thanks for the supportive reply! I’ve toyed with this idea since the
Liberty began offering the 2.8L CRD option. At Moab, after a closer look at the J8 package, the concept gelled. I
spoke with some Mopar colleagues about the prospect. As the result of some research, interesting facts have
Mopar Underground staff has played with Liberty engine swaps, and
apparently, the computer (PCM) has a key code that interfaces with the ignition switch. This safety/security
approach means that the ignition switch must be an integral part of the swap. Based upon the Underground’s
resources, they use a donor Liberty model and swap out the engine/transmission plus the entire Liberty steering
column. It’s possible that the J8 does not have this level of sophisticated PCM security. Imagine the consequences
if a military J8 operator were to misplace the keys to the vehicle! Given that proviso, I would be game for the
swap if enough readers like the diesel concept and if the projected costs are practical. I would swap the
engine-transmission unit and mate it to the XJ’s existing NP231 or a J8 transfer case, or possibly an Atlas II from
Advance Adapters. I would do the swap with all electronics and wiring included.
If the prospect has a following, my aim would be to encourage Mopar to
offer a “package” of assembly line pieces that make up the swap. It would be necessary to make the complete J8
powertrain available through Mopar, as consumers would find it impossible to buy a surplus Egyptian military
vehicle. All of this requires a commitment from Mopar.
One thing is clear, Matt. 30 mpg on the highway and peak engine torque of
295 lb-ft at 2000 rpm for backcountry crawling are the performance gains we should all want at this point. Fuel
costs won’t get any cheaper, especially with oil spilling into the Gulf of Mexico and fostering an ecological
nightmare for Gulf States residents. A high-tech, EFI/CRD 2.8L four might be just what modern ‘wheelers
To whet appetites, here’s a rundown on the VM 2.8L engine performance (data
courtesy of a Wiki entry on the J8 subject):
J8 Engine and Transmission...
The engine for the MILSPEC J8 is manufactured by VM Motori S.p.A. based in
Engine code: R 428 DOHC "Panther"
Displacement: 2.8L (2766 cc).
This engine has four valves-per-cylinder and common-rail direct fuel
injection technology. It is essentially an R 425 DOHC 2.5 L (2499 cc) enlarged to 2.8L.
Max Power: 118 kW (158hp) @ 3800 rpm
Max Torque: 400 Nm (295 lb-ft) @ 2000 rpm
The Transmission is a Chrysler 545RFE five-speed, electronically controlled
automatic linked to a Command Trac 4WD system with 2.72:1 low range.
This 545RFE is in turn based off the 45RFE 4-speed transmission with the
addition of a 5th forward gear.
Standard Ratios are:
2nd Prime 1.50:1
Worth noting, AEV has an in-place 2.8L CRD conversion that suggests some
cost obstacles. For more information on AEV’s approaches, there are comments at the AEV
If this swap and a J8 type vehicle are as costly as AEV indicates, we’ll be
back to the drawing board for XJ Cherokee owners. Unless readers can benefit from a practical, affordable way to
defeat high fuel costs, using a contemporary, hi-tech, clean tailpipe diesel, I have no designs on installing a J8
powertrain in the magazine’s test-bed XJ. At 4WD Mechanix
Magazine, it’s about technology that meets readers’ needs and
I’m open to readers’ thoughts on engine alternatives, with these caveats: a
clean tailpipe, improved performance and an affordable approach.
I’ve peeked at the Cummins offerings, as I’m thrilled with our ‘05 5.9L Ram
six-cylinder engine! In four-cylinder industrial versions, however, the Cummins is too heavy and shows unimpressive
output. Any experience with an Isuzu or Mercedes medium duty truck design?
Cost must be reasonable and amortize quickly as fuel savings. The swap must
be affordable for an XJ/TJ or JK owner, with substantial performance and mileage gains.
I would do the entire swap in a step-by, instructional format. This
includes mount fabrication (engineering, welding and fitment), detailing all modifications (cooling, electronics,
exhaust solutions, transmission, driveline, wiring, etc.); the sources for swap pieces, costs as you suggest and,
ultimately, some bona fide, “real world” testing of the package before others commit.
Thanks for your interest in the magazine and its projects, Matt. We’ll stay
in contact and weigh other readers’ responses and ideas. I’m more than ready for clean tailpipe diesel power in the
XJ Cherokee—or any other Jeep model!
Two Jeep Cherokees Need Exhaust
I saw your article on the exhaust upgrade you did on a
‘99 Jeep Cherokee. I would like to do the same modification on my 2000 Jeep Cherokee. Is this
I talked to a Borla specialist. Their kit was not tested
on the ’98-’99 XJs. I will definitely go with the ‘00-‘01 kit. Your article will be helpful if I run into
minor misalignments. Thanks for your advice.—Vago
Note: Jennifer and Vago refer to my
XJ Cherokee exhaust system article in OFF-ROAD Magazine. When routing the tailpipe between the frame and
right rear spring, be aware that our XJ chassis has a 6-inch lift kit installed! Stock spring arch may not
provide enough clearance here...Changing a 4.0L Wrangler, Grand Cherokee or XJ Cherokee exhaust manifold is a
major task. In the article, I show how to save time swapping manifolds. Even so, this is a complex job that
requires the right tools, time enough to get the job done right plus
cutting-welding equipment for the hanger changes…
For the magazine project, I used the 1997 Borla XJ kit for our
1999 XJ Cherokee chassis. At the time, Borla only offered Jeep XJ systems to fit through 1997, essentially
kits still supplied to Mopar Performance. The Borla header is identical for TJ and late XJ applications,
including the ’99 model. Borla’s ’97 XJ package includes the Borla header, header-to-cat pipe, a performance
muffler and a new tailpipe plus high-quality clamps. For peak performance, I added the Random Technology
catalytic converter. This package turned out to be a good approach. Only four modifications were needed to
fit the system to this 6” lifted ’99 XJ chassis: 1) a modification to the head pipe-and-cat support bracket
that fits at the transmission mount, 2) careful routing of the tailpipe with a drop bracket to relocate the
attachment point for the axle position tailpipe hanger, 3) making an offset bracket to position the tailpipe
away from the fuel tank at the tank position hanger, and 4) careful routing of oxygen sensor wires and
wires from the crankshaft-flywheel position sensor. (Keep wires and plastic convolution shield routed away
from the header heat!) As for gains from this installation, Borla’s superior quality pieces replace the
crack-prone factory header and a stock head pipe that is highly restrictive. Dyne-tested, Borla’s scavenging
gains are legend. For quality and fit, Borla is tops. If the stock exhaust manifold has a crack, the Borla
system is a very wise replacement. In terms of installation difficulty, a header swap is complex—just
like replacing a stock manifold. Be aware that a major tune-up—including new plugs, cap, rotor, air filter
and plug cables—accompanied this exhaust system installation. With the exhaust system upgrade and tune-up,
mileage jumped 2.8 mpg on the highway at cruise! (Mileage gains tend to vary; realistically, though, the
engine now breathes freely and accelerates much better than prior to this work.) Before investing this kind
of effort, you might try a major tune-up first, and see how much of the 2.8 mpg gain is achievable with just
tuning. As I emphasized in the OFF-ROAD Magazine article, periodically tuning the engine and
installing a clean air filter will improve fuel efficiency and performance…For those interested, I do tune
with genuine Mopar filters and ignition components…