Q&A How-to for 1962-91 Full-Size Jeep (FSJ)
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Cherokee 360 V-8 Overheating
Q. From: FRED
September 12, 2011 3:38 PM
To: 4WD Mechanix Magazine
Overheating fsj Cherokee
I have an overheating problem on my 1979 Cherokee that has me at my wit's end.
Here are the facts
It has a 360 v8, t400 tansmission, quadratrac
I purchased it a few years ago, the seller advertised it as a rebuild engine and transmission but had no
I live in Phoenix, AZ and in the summer, it normally runs at about 200 degrees, according to it's aftermarket gauge
for the first 20 minutes, then the temp will start creeping up (faster if I use my A/C) and will rise past 260 if I
This is all freeway driving
I have confirmed the temp with an IR thermometer.
I have replaced the following parts to try to hit the cause:
Radiator (new aluminum crossflow for Bjs Offroad)
thermostat (a few different ones including high flow and even tried removing alltogether)
Fan clutch (heavy duty)
flushed out cooling system a few times
pressure tested fine
passed chemical head gasket test kit
cylindar compression is consistent.
fan shroud is in tact
It seems fine when air temp is below 85
I'm starting toi think it's just a worn out engine or the so called rebuild in the engine or trans was botched and
the excess friction is causing the overheating
But other wise the engine runs fine and the trans shifts smoothly
Can you give me your thoughts? I love the truck but I'm at the point where I can't trust it not to leave me
Thanks for listening
From: 4WD Mechanix Magazine
Overheating fsj Cherokee
Date: Mon, 12 Sep 2011 19:38:27 -0700
problem, Fred, with lots of effort at finding a remedy. Here are some ideas, given the work you have done:
1) You did not mention transmission cooling, although it’s assumed the aftermarket radiator has a built-in cooler.
IR your cooling lines on each side of the transmission cooler if integral to the radiator. Excessive heat here can
migrate to the engine coolant section of the radiator. Consider an add-on transmission cooler to supplement the
2) I always run a thermostat, as leaving it out can actually permit too much flow, resulting in inadequate time to
cool down the engine coolant. A 180-degree thermostat would be right for your climate.
3) The fact that your A/C causes rapid heat-up indicates inadequate radiator capacity or the need for a fan shroud,
which you did not mention. The fan needs to capture and pull air through the fan side of the radiator, drawing from
the largest surface of the radiator.
4) Make sure the by-pass hose is a molded type and not restricted in any way. Use OE-type molded radiator hoses,
As a rule, overheating at low speeds is an air flow problem. Overheating at cruise speeds and higher, without a
load, is a radiator GPM flow rate problem, typically an inadequate radiator. I am not pointing the finger at the
aftermarket radiator but you should check with the manufacturer about the flow rate and capacity. Compare this with
an OEM radiator for an air conditioned Cherokee with the 360 V-8.
Since you did replace the fan clutch, we should be able to rule that one out, although you should hear a “heavy
duty” fan clutch unit spool up the fan as the engine gets hotter. If you do not hear fan noise at the temps you’re
describing, the fan clutch might not be working. It is thermally controlled and should cause the fan to drive at
Use your IR thermometer to spot-check the engine, radiator hoses, radiator and transmission cooler for localized
overheating. A cheap “engine overhaul” with block mud left in the lower areas of the block can be a cause of
overheat. Mismatched head gaskets or heads can be an issue, too, as cooling ports will not align. A thorough
rebuild includes hot tanking the block and heads. Check all areas of the engine castings for hot spots.
Let me know about the shroud and fan clutch, the radiator flow rate and which thermostat you’re using…
Q. From: FRED K
September 13, 2011 10:34 AM
To: Moses Ludel
Overheating fsj Cherokee
Thanks for the
The transmission does not cool through the radiator, I have an external cooler that currently hangs from the front
bumper (to rule it out as preventing air flow)
The fan shroud is in place and intact
All hoses are molded
The fan clutch does speed up as the temp increases
Thermostat is a 195 degree (stock temp) Robert Shaw
I don't have any gpm stats on the radiator but can tell you it does cool a little better than the stock 4-core I
had previously. I'll see what I can find on the rad specs and take some tempaerture readings and let you know
Thanks for your help
A. From: 4WD Q & A
Tuesday, September 13, 2011 3:54 PM
To: 'FRED K'
Subject: RE: Overheating fsj Cherokee
have been thorough. Do the IR spot check and let’s see where that leads. I would also like to know that the
ignition distributor’s advance mechanism works. You can set base timing properly, yet with a defective or sticking
advance mechanism, you will not have the correct total number of advance degrees.
You can test
the distributor in a distributor machine or with a timing light that has a built-in advance. If you do test the
distributor on the engine, I recommend doing this with the fan belt(s) removed and the engine cold. This way, you
can rev the engine to the distributor rpm needed to verify full advance—without risk of the fan separating from the
water pump. Testing the vacuum advance, if so equipped, is easy: this can be done at idle with a vacuum hand pump
on the vacuum canister line.
the AMC V-8 timing cover is a source of contention for oil pressure and coolant flow…Look into the coolant
distribution. Oil pressure gains are also possible from a timing cover
230 OHC Six: Echoes of the
Sent: Monday, June 13, 2011 10:34 AM
To: 4WD Mechanix Magazine
Subject: Willys Tornado 230 engine FI update
Dear Mr. Ludel,
I have the infamous Tornado 230 OHC six in our '65 Willys wagon
and like it. Although it is obviously smaller than the 4.2
sixes, it runs very well but smokes a bit. Before I do a minor (or
major) rebuild, do you know anyone who has done a fuel
injection retrofit on this unique-to-Jeep engine? Since the engine has a
long stroke it is ideal for my needs, but I would like to clean up
the tail pipe emissions and make it more economical if possible and practical.
I know that IKA (Industry Kaiser Argentina) did a lot of
development with this engine (7 main bottom end and new cylinder head with individual intake runners, etc.),
but has anyone in N. America played with this engine?
Thanks for any information...
PS: I really find your
technical articles useful - they are wonderful and straight forward to follow.
PPS: I have upgraded the
Tornado ignition system using Brent Picasso's MegaJolt Lite System which works beautifully but realize you
are associated with Mopar and so might see a Ford derived ignition as heresy! Perhaps you can forgive me! If interested, you
can see my very amaturish efforts here:
Hi, Pavel...Nice to get your details on the 230
OHC. I am intrigued about the 7-main bearing lower end and how that
block mates with the other 230 components. Is the 7-main block
available in numbers?
The smoking is virtually inherent with the OHC
six. These engines are notorious for valve guide seal and valve
guide oil seepage. If the engine blows blue smoke on start-up after
setting for a while, suspect guide and/or seal issues.
EFI is not far-fetched. TBI is the simplest approach, and a system like
the Howell for the 258 AMC six would be in the ballpark for throttle body sizing and fuel
flow. This is a kit approach with all hardware, the throttle body,
an ECU, wiring and plumbing. You would need to adapt the throttle
body to the 230 intake/carburetor base pattern.
A stock 230 cylinder head design lends itself to TBI, not port
injection. The limitation is the two manifold runners with three-cylinder internal passageways within
the cylinder head. The update head, if you can fit one to your block, would provide the port injection
Although two manifold runners
could be run with a port injector per runner, this would require heavy flow per injector, an unrealistic goal.
The Howell system (or your own G.M. TBI and ECM design) will fit atop a carburetor manifold. Howell uses
G.M. off-the-shelf TBI as the platform for his kit. (Bill is a former G.M. engineer.) The common G.M. throttle
body for Throttle Body Injection (V-6 and V-8 applications) provides a place to
start. A simpler installation, stock TBI or the Howell kit is a
Although some equate TBI to an "electronic carburetor", it is much more sophisticated and
would dramatically enhance your current engine with its two-runner intake manifold. You want a system with an
oxygen sensor and MAP sensor feedback (plus the other G.M. OEM sensor signals).
G.M. TBI is an uncomplicated speed density design.
would expect good torque and horsepower gains with a bolt-on TBI system. The original Mopar EFI conversion for
the 258 was actually a Holley TBI unit fitted to the stock 258 intake manifold's carburetor flange. Ignition and
fuel curves were part of an aftermarket Electromotive fuel and spark management system that was laptop
programmable. This, of course, complicated the tuning side of this package. Using the stock manifold, gains of
40-50 horsepower were possible.
The later Mopar EFI kit with MPI improved both horsepower and torque gains. This was a simple
retrofit with the common 232/258/4.0L inline six's individual intake runners. An interchangeable distributor
design made the spark management easy. The later MPI kit essentially retrofitted a 1995 4.0L fuel-and-spark
management system to the earlier AMC sixes...Your 230 OHC does not have the six intake runners or head ports to
accomplish an MPI installation.
Trust this helps...Moses
OHC 230 Chat
Sent: Wednesday, June 15, 2011
To: 4WD Q & A
Subject: Re: Willys Tornado 230 engine FI update
Hello Moses -Thank you for the quick reply. I have interspersed my comments/questions with the
remarks you send me... see below please...
2011-06-14, at 8:13 AM, 4WD Q & A wrote:
> Hi, Pavel...Nice to get your details on the 230 OHC. I
> about the 7-main bearing lower end and how that block mates with the
> other 230 components. Is the 7-main block available in
Pavel writes: I have read
that IKA (Industry Kaiser Argentina) made a large number of updated (7 mains) engines for use in their so-called
"Torino" sedans - these were very similar to American Motors Ramblers. The engine mounts were moved to a more
midpoint on the block from the front plate, oil filters changed sides, etc., but the real difference I'm interested
in was the updated head that had individual intake runners not the arrangement on our engine where there were only
two intake ports with internal runners to three cylinders each.
I believe the Argentine engines had at least two or
three different intake manifolds which held Holley 2-barrel carbs or even triple side draft Webers (about 1300 were
made). In racing form, the fully developed engine reached about 330 hp at high revs!
Unfortunately, your 230 does not
offer that cylinder head design. Unless the Argentine head can be retrofitted, I would be content with a TBI conversion that involves complete electronic fuel-and-spark
You would need to modify your existing ignition distributor to work with a G.M. electronic
control module (ECM). Mopar's EFI conversion uses a bolt-on crankshaft sensor pickup to signal TDC for #1
piston. Aftermarket pickups are available from MSD and Edelbrock if needed. MSD has solutions for
converting the distributor to work as an electronic trigger. There are ignition coil solutions from Mopar
for your converting the distributor to work like a Motorcraft electronic unit, see the photo on the home
page of the magazine. I converted a vintage Motorcraft dual point unit (from a Ford Mustang 289
K-model V-8) to electronics. AMC was fond of its Ford-sourced Motorcraft ignitions, which accompanied the Jeep
models into the Chrysler era. The last Motorcraft ignition was in the 1991 Grand Wagoneer 360 V-8.
I discuss upgrades to the AMC six-cylinder units in my Jeep® Owner's
Bible™. Unlike the
Prestolite distributors, the Motorcraft units were reliable and durable.
the motivation is high enough, TBI is feasible—even for a Kaiser-Jeep 230 OHC inline
Keep me posted, Pavel...
230 OHC Discussion continues...
Sent: Thursday, June 16, 2011 9:12
To: 4WD Q & A
Subject: Re: Willys Tornado 230 engine FI
Thank you again for the information,
Moses. A TBI unit with oxygen sensor
and MAP sounds like a wonderful "fit" for our old Willys Tornado.
If my attempted Argentine
link works out, you have outlined the logical and more involved/expensive next steps toward MPI or port injection.
I don't require the best result, only measurable improvements on all fronts plus the pleasure of modernizing an old
but interesting engine.
First, I must get new valve
guide seals on the unit and see if I can squeak through Aircare ( I flunked last
I will contact you again if
there is any substantial progress—it will take some time.
I really appreciate your
Pavel...For passing your Aircare program, the guide seals should help. Run a cylinder
leakdown test before beginning this work to confirm that the rings and valves seal properly. A leakdown test
will pinpoint valve, head gasket and ring leakage.
You can carefully install guide seals without cylinder head removal by first lifting out the
camshaft. Using an air-hold at each spark plug hole with the piston at TDC and both valves closed, place a
straddle type valve spring compressor over the valve spring. With care, while keeping the valves seated
with air pressure, replace each guide seal. All of this is described in the factory workshop manual for
the 230 OHC engine. You should have a copy of this manual; it is available in reprint as the "Service
Manual 'Jeep' J-Series Vehicles". Try Willys Jeep Parts and other sources for this
The cure for these guide issues is head removal, installation of silicone bronze guide inserts
in the original cast guides and use of Perfect-Circle style, nylon wiper valve guide seals. Guides may require
machining to accept these seals. A shop that does valve work is qualified to perform this
modification. P.C. replacement seals were the remedy for this engine and quickly adopted for high
performance engine applications. Use compatible valve stem materials with the silicone bronze guide
Once you get past the head and guide issue, remember that Holley carburetors are very
touchy. A time-well-spent "blueprint" rebuild, using the right jets, power valve and other parts, can get
that crude carburetor to behave itself—and pass your Aircare test. Be sure the PCV system works properly,
too. If you need OEM Holley specs, let me know. Some are listed in the Jeep manual that I
Keep me posted...
Grand Wagoneer Ignition Spark
I have an ’89 Grand Wagoneer with a mild lift and multi-purpose goals. The ignition distributor
has been replaced with an HEI type that has centrifugal and vacuum advance. The distributor came with a universal
spark curve. I’d like to re-curve this distributor for performance and fuel efficiency. My thought is to push the
advance "all in" a touch earlier if I can get the jetting right in the carb. Running this engine at much above
4,000 rpm is a rare occurrence although I do plan to curve the distributor in the engine. (I do not have access to
a distributor machine anyway.) Fattening the jetting should help reduce pinging under load. In the past, on
performance engines (which this one certainly isn't now) I’ve always worked to get the mechanical timing all in by
about 2500-3000 rpm with good results, but of course those engines tended to run more aggressive camshafts and
carburetion. Do you think I am asking for trouble if I take this direction?—Marc
Marc, the old racing formula
for aftermarket distributors has been to reach full centrifugal advance degrees by 2000 rpm. This is fine for an
engine without vacuum advance and with A/F ratios richer than stoichiometric for gasoline (14.7:1). Considering the
Grand’s weight and stock jetting of the carburetor (lest we forget, your aims include fuel efficiency), I would try
the curve that I have provided here. You can bump up the base timing if octane/detonation is not an issue,
increasing the total number of advance degrees, although it is doubtful that a 360 AMC V-8 will tolerate more than
34-36 crankshaft degrees total advance on today’s typical pump gas. “In the day,” we built muscle small block V-8s
that ran 38-42 degrees total advance—with a cam, richer jetting and 100-plus octane fuel.
You can fiddle with a more radical curve, but as you hint,
that could be anathema without bumping up the camshaft’s valve overlap and enriching the fuel mixture—neither of
which will do any good for fuel efficiency. (Incidentally, my camshaft choice for low-end power, torque and fuel
efficiency remains CompCams’ 252 grind. This has stronger lift with milder duration and overlap.) I would add that
an MSD timing control would simplify base timing control once you have the curve established. The timing control
can be handy for varied altitudes, loads and driving conditions. You can set base timing (affecting maximum degrees
of advance as well) from the dash.
If you decide to abandon the fuel saving plan and build a
racier engine, let me know. We can “blueprint” spec a distributor following the hotter AMC V-8
Javelin/AMX requirements; however, the octane needed for the compression bump will be expensive and possibly
difficult to source on your hinterland trips. In my view, for trucks, tow vehicles and off-roading in the manner
you would typically pursue with a heavyweight Grand Wagoneer, a muscle car engine build is
I pulled a distributor curve for your Grand Wagoneer’s
relatively stock 360 V-8. I looked over the late muscle era AMC listings for the 360 and 390 V-8s. They were
emission burdened with an advance/retard vacuum mechanism. Therefore, the specs provided here are for a pristine
1971 J-truck application that uses a Delco-Remy window cap distributor. Truck engines were less emission
restricted, and this respectable curve should work with current octane fuel and your 360’s compression
I converted rpm to crankshaft speed, as you intend to curve
your distributor in the engine. (With the engine cool, disconnect the fan belt before running the engine to 4,400
rpm! Keep the engine cool during spark curve tests.) When setting the curve with the distributor in the
engine, set your base timing to zero prior to adjusting the curve. Use a timing light that has a built-in advance
to simplify readings at higher rpm.
This is an effective curve for performance, economy and
resisting detonation. Once you have the curve set, you can fiddle with base timing to combat detonation (“ping”).
With a base timing of 2.5 degrees BTDC, I would anticipate 34-36 crankshaft degrees of total advance, using octane
and detonation as a guide. Here are the specs:
1971 Jeep 360
truck V-8, distributor #1111948 (D-R breaker point); base timing 2.5 crankshaft degrees BTDC set with vacuum line
disconnected and taped, engine at idle speed of 650 crankshaft rpm…I have expressed all specs below in crankshaft
degrees to simplify your tuning. If you use a distributor strobe machine, divide degrees and rpm by two to
represent distributor degrees and speed:
advance (crank degrees with vacuum advance hose disconnected and taped): Zero to 5-degrees at 900 crankshaft rpm;
16-21 degrees at 1580 crankshaft rpm; 17-21.2 degrees at 1610 crankshaft rpm; 28-32 at 4400 crankshaft
#1115362)—0 degrees at 4-6 in/hg; 24 degrees at 18-19.3 in/hg…If the vacuum canister is adjustable, you can set the
vacuum advance using a hand pump with a vacuum gauge. Keep engine speed low enough to prevent centrifugal advance
from interfering with measurements.
'in the day' tuning equipment for FSJs—distributor strobe machine and Motorcraft V-8 distributor undergoing recurve
work at right.
I trust this truck-based approach helps with overall
performance and efficiency, Marc. Let me know the results!