258 head swap?

Ive been reading about the 4.0 head swap for 4.2 motors. Is this really as
good as it sounds or are there more headaches to be found?

What all has to be replaced besides the head?

Have to be fuel injected then?

40hp gain? really?

Steve G wrote:
> Ive been reading about the 4.0 head swap for 4.2 motors. Is this really as
> good as it sounds or are there more headaches to be found?
>
> What all has to be replaced besides the head?
>
> Have to be fuel injected then?

It depends on whether the 4 liter head takes the same intake as the
4.2. If not there may be a carb manifold or, you could fabricate one
were you so inclined. Even if you are not a highly skilled welder, you
could learn enough gas (oxy-acy) welding to tack it and have it done by
a pro.

Three Webers, that's the ****.

http://www.monsterslayer.com/jeep/40Head/40Head.htm
http://www.off-road.com/jeep/new/40conv.html
http://www.visi.com/~bsimon/jeep/mpi_dirs.html
God Bless America, Bill O|||||||O
http://www.billhughes.com/

Steve G wrote:
>
> Ive been reading about the 4.0 head swap for 4.2 motors. Is this really as
> good as it sounds or are there more headaches to be found?
>
> What all has to be replaced besides the head?
>
> Have to be fuel injected then?
>
> 40hp gain? really?

L=2EW. Hughes III (=DFill) wrote:
> http://www.monsterslayer.com/jeep/40Head/40Head.htm
> http://www.off-road.com/jeep/new/40conv.html
> http://www.visi.com/~bsimon/jeep/mpi_dirs.html
> God Bless America, Bill O|||||||O
> http://www.billhughes.com/
>
> Steve G wrote:
> >
> > Ive been reading about the 4.0 head swap for 4.2 motors. Is this really=
as
> > good as it sounds or are there more headaches to be found?
> >
> > What all has to be replaced besides the head?
> >
> > Have to be fuel injected then?

As is so often the case we fail the reading Comprehension Test.


JEEP 4.2 LITER (258 CID)
MULTIPOINT FUEL
INJECTION KIT

INSTALLATION INSTRUCTIONS

Mopar
PERFORMANCE


INSTALLATION INSTRUCTIONS

JEEP 4.2 LITER (258 CID)
MULTIPOINT
INJECTION KIT
P5249610 For Manual Transmission Vehicles
P5249686 For Automatic Transmission Vehicles

THIS KIT IS EMISSIONS EXEMPT IN THE STATE OF
CALIFORNIA UNDER C.A.R.B. EXECUTIVE ORDER D265-7
THE TUNE UP PROCEDURES AND ENGINE SERVICE ARE
THE SAME AS A 1994/1995 4.0 LITER JEEP WRANGLER

PLEASE READ THESE INSTRUCTIONS THOROUGHLY
PRIOR TO INSTALLATION OF THIS KIT

CHECK YOUR PARTS AGAINST THE BILL OF MATERIAL INCLUDED IN THE KIT
(Attached to instructions)

This product is intended for use on STOCK, UNMODIFIED, WELL MAINTAINED
1981-1990 4.2 LITER (258 cid.) ENGINES. Installation on engines with
MODIFIED
CAMSHAFTS, INCREASED COMPRESSION RATIO or engines that are in POOR
MECHANICAL
CONDITION, such as LOW CRANKING COMPRESSION or EXCESSIVE OIL
CONSUMPTION
is not recommended.

NOTE: If spark knock (detonation) occurs, it is recommended that 92
octane or
better premium fuel be used. The use of Mopar combustion chamber
cleaner will
reduce carbon deposits and help reduce spark knock.


DISASSEMBLY:

1=2E Disconnect the ground cable from the battery and drain the coolant
from the
radiator.

2=2E Loosen the power steering pump and the alternator and remove the
drive
belts. Remove the two bolts that hold the power steering pump to the
water
pump. Remove the two nuts from the rear power steering pump bracket,
then
slide the pump forward to disengage it from the rear bracket. Remove
the rear
bracket from the intake manifold.

3=2E Remove the air cleaner assembly as a unit and discard it.

4=2E Remove all of the production emissions controls from the engine,
including
the three (3) solenoids located on top of the valve cover, the vacuum
switch
assembly and any lines and delay valves connected to the carburetor.

NOTE: Refer to the Production Emissions Schematic or to a proper shop
manual
for your particular year vehicle.

5=2E Remove the pulse air valves, which inject fresh air upstream and
downstream
of the catalytic converter, and all associated fittings.

6=2E Disconnect the heater hose from the fitting on the intake manifold.
Remove
the throttle linkage and throttle cable. Remove the carburetor/intake
manifold
assembly. This will require removing the tube that connects the
exhaust
manifold to the EGR valve mounted on the intake manifold.

NOTE: It is not necessary to remove the exhaust manifold.

7=2E Remove the stock mechanical fuel pump and fuel lines from the
engine. Make
sure to mark the lines PRESSURE and RETURN where you disconnect them at
the
fender well.

CAUTION: GASOLINE IS HAZARDOUS!! Wear eye protection and never work on
a HOT
engine or around FIRE OR FLAME!

8=2E Disconnect the upper and lower radiator hoses and remove the
radiator, fan
shroud, engine fan, thermostat housing and crankshaft pulley.

9=2E Remove the plug wires and distributor cap. Remove the #1 spark plug
and
rotate the engine in its normal direction until the #1 piston is on the
compression stroke. The timing mark on the dampener should line up
with the
"O" mark on the timing tab. Looking through the stock fuel pump
mounting boss,
rotate the engine backwards until the camshaft moves and note the
amount of
slack in the timing chain as degrees on the timing tab. If the slack
is more
than 10 degrees, replace the timing chain. Rotate the engine in the
direction
of rotation to the "O" of the timing tab. Note the clocked position of
the
distributor rotor. Loosen the hold down clamp and remove the
distributor.
Remove the ignition coil and bracket and discard them.

10. Using a suitable puller, remove the crankshaft dampener. You will
need a
new dampener, P5249688 for serpentine belt, or P5249687 for V-belt
driven
pulleys.

11. Remove the brake booster fitting from the old manifold and install
it in
the new manifold.

12. Remove the windshield washer bottle and the charcoal fuel
cannister. Be
sure to mark the vacuum lines that go from the fuel cannister to the
intake
manifold and the fuel tank.

13. Remove the front three (3) driver's side oil pan bolts.

14. Remove the oxygen sensor from the exhaust manifold.

15. If the vehicle has a catalytic converter, it will be necessary to
seal the
air injection tubes at the CAT and header pipe. Seal by bending the
end of the
tube and crimping.


ASSEMBLY:

1=2E Install the new oxygen sensor in the exhaust manifold.

2=2E Cut off one end of the tube that went from the exhaust manifold to
the EGR
valve and remove the tube nut from it. Install the saucer shaped
freeze plug
into the hole in the exhaust manifold where you removed the EGR tube.
Secure
the freeze plug by tightening the now free tube where nut down against
the
freeze plug.

3=2E Install the new distributor (The distributor is shipped with an
indexing
lock pin and will not rotate. DO NOT REMOVE THE PIN UNTIL THE
DISTRIBUTOR IS
INSTALLED).

NOTE: If you think the engine may have moved from TDC, make sure the
engine is
at TDC on the crankshaft balancer. Install the hold-down clamp and
remove the
white locking pin.

4=2E Install teh conbination fuel pump block-off plate/ignition coil
bracket
where you removed the original fuel pump. Install the coil with the
plug
wire terminal toward teh distributor.

5=2E Install the new crankshaft dampener. (Torque the bolt to 120 ft.
lb.)

6=2E Install the pickup sensor bracket. The bracket bolts to the oil pan
where
you removed the three (3) bolts in step #13 of the disassembly
instructions.
Install the pickup sensor on the bracket with the bolt provided. NOTE:
There
should be between .020" and .060" clearance between the sensor and the
crankshaft dampener. This clearance is the thickness of the paper
button on
the end of the sensor. You push the sensor up against the dampener,
then
tighten the mounting screw. This will set the initial clearance.

7=2E Install the crankshaft pulley, the fan, and the radiator. Install
the new
195 degree thermostat. This is critical. Temperature level of 195
degrees is
critical for fuel system operation. Install the coolant sensor
supplied into
the new thermostat housing in the 3/8" pipe hole, then reinstall this
new
assembly on the engine. Reinstall the radiator hoses and heater hoses;
reroute
the new heater hose supplied, as it no longer goes through the intake
manifold.

8=2E Install the new intake manifold. You will only be able to reinstall
one of
the power steering pump bracket bolts and You may have to trim the top
lip off
of the power steering pump bracket to make it fit the new manifold. DO
NOT
over tighten the bolts! Bolt torque is 23 ft. lb.

9=2E Install the throttle cable and bracket.

10. On automatic transmission vehicles: the kickdown linkage must be
installed
Once these parts are assembled, you should set the adjustment. Rotate
the
throttle body to wide open throttle. This will cause the cable to
ratchet to
the proper zero clearance. At this time, verify that the throttle
linkage
works smoothly and returns to IDLE (closed throttle).

11. Reinstall power steering pump bracket and belts. Tension the
belts. The
hole in the bracket may need to be enlarged slightly.

12. Connect the new fuel lines to the fuel rails and attach to the
mounting
bracket on the new intake manifold. Find the fuel inlet line where it
was
connected to the stock mechanical fuel pump (NOTE: Some CJ models have
the fuel
supply line routed down the right passenger side of the vehicle.) Trace
this
line back across the engine bay to the driver's side frame rail. Cut
this line
and the fuel return line a few inches behind the front leaf spring eye.
Bend
them up slightly to align with the new fuel lines that come from the
MPI fuel
rail. Connect the lines with the 5/16" fuel hose and clamps provided.
NOTE:
The new fuel lines look almost identical. You will note that one has
an orange
dust cap over the quick connect. This is the return line, or fuel out,
and has
the smaller 0-rings inside. It connects to the new fuel rail on the
forward
end of the line coming out of the fuel pressure regulator. The
pressure line
has a yellow dust cap over the quick connect which has the larger
0-rings
inside and connects to the second connection on the fuel rail. IT IS
IMPERATIVE THAT THESE LINES ARE CONNECTED PROPERLY. Improper
connection can
cause damage to the fuel pump. THE RETURN FUEL LINE GOES FROM THE FUEL
REGULATOR (on the fuel rail) BACK TO THE FUEL TANK.


NOTE: On models with the fuel supply line on the right side, carefully
route
the line around to the fuel rail similar to the O.E. setup.

CAUTION: If you buy any fuel line to hook up the fuel pump, make sure
it is
rated to handle EFI pressures!

INSTALL FUEL PUMP AS FOLLOWS:

13A. Jack up the rear of the vehicle and place on jack stands. From
under the
vehicle looking to the rear you will notice a cross member in the frame
above
and behind the axle housing. On the driver's side of this cross member
you
will notice a rubber block with three (3) flexible fuel lines emerging
from it.
The lines turn 90 degrees toward the frame and are connected to hard
lines with
clamps. On the flange of the cross member are three (3) bolts that
attach the
fuel tank skid pan to the cross member.

13B. Remove the center bolt.

13C. Disconnect the center fuel line from its hard line at the clamp.
Reconnect this flexible line to the inlet of the new fuel pump assembly
using
the same clamp.

13D. Mount the fuel pump assembly to the cross member flange using
the nut
and lock washer.

13E. Connect the 5/16" flexible line coming off the new fuel pump
assembly to
the fuel filter inlet line, with the clamp provided, and the fuel
filter outlet
to the center hard line of the original fuel line.

14. Install the new charcoal cannister in the stock location and hook
up
the new vacuum lines. Some engines will not use the plastic valve cover
fittings. The many different valve covers have different PCV and fresh
air fittings. Make sure to use the stock 258 PCV valve or orifice at
one
end of the valve cover and provide fresh air at the other end of the
cover.
It is important that the engine is ventilated properly to meet
emissions and
reduce oil leaks caused by crankcase pressure.

15. Install the new Powertrain Control Module (PCM) right above the
charcoal
cannister on the bulkhead with the supplied hardware.

16. Plug in the wiring harness to the PCM using the 60-pin connector.
DO NOT
OVER TIGHTEN THE CONNECTOR! Drape the harness over the top of the
master
cylinder, then around the back side of the engine.

CAUTION: THE HARNESS MUST NOT BE CLOSE TO THE EXHAUST, USE TIE WRAPS TO
SECURE
IT OVER THE MASTER CYLINDER.

17. Find the two relays on the harness a short distance from the PCM.
Mount
them to the bulkhead with the screws provided. NOTE: Mount the relays
with the
wires pointed down. This is to prevent water build-up within the
relays. The
PCM may be mounted at any angle, however, do NOT mount it with the wire
connector facing up. This would allow water to pool in the connector!
The PCM
is waterproof. The 60-pin connector is splash proof, but will not work
when
immersed in water.

18. Mount the MAP sensor to the bulkhead right behind the engine with
the
screws provided. Plug the green three (3) prong plug from the harness
into the
MAP sensor.

19. Route the harness down along the valve cover toward the front of
the
engine. Connect the fuel injectors. Each one is marked where it goes.

20. In the center of the harness between injector plugs #3 and #4 is a
group of
four plugs. Connect three (3) of these to the throttle body in their
respective receptacles, and the fourth one to the Manifold Air
Temperature
(MAT) sensor.

21. In the harness at the front of the engine is another group of three
(3)
plugs. One of them is very long; this is the Oxygen Sensor plug. The
three
(3) prong plug in this group is the pickup sensor plug. The other (two
prong)
plug is the coolant sensor plug. These will only plug in to the
correct
sensors. Secure the cables with tie wraps provided. Make sure the
pick up
sensor connector is tied away from the exhaust manifold.

22. Bend the harness toward the passenger side of the Jeep and down
along the
spark plug side of the head. The next plug is the ignition coil
connection.
Then comes the harness ground with the distributor plug. Connect the
harness
ground under the bolt that holds the dipstick tube to the engine block.
(it has
other ground wires on it. Do not remove any.) Connect the distributor.

23. Route the rest of the harness along the top of the transmission.
The next
plug will be the vehicle speed sensor. Route the remaining harness
along the
frame rail to the rear of the Jeep' to connect the fuel pump power (+)
to the
green wire with the black stripe. The ground wire is black with an
orange
stripe. Secure the harness all along its length in strategic locations
with
the tie wraps provided. Make sure that there is clearance between any
moving
parts or areas of high temperature, such as the vehicle exhaust. You
may want
to use dielectric grease on the connections to prevent corrosion (Mopar
part
number J8126688).

24. To supply a switched 12 volt power supply to the two bulkhead
mounted
relays, locate the old positive (+) side coil wire (usually a yellow
color).
Connect this wire to the relay wire. Now connect the red relay wire to
the
starter relay, battery plus(+). The starter relay is usually located
under the
battery box or mounted on the fender panel. Mount the system fuse.

NOTE: Make sure that the switched 12 volt wire is not routed thru a
ballast
resistor or resistance wire. Also make sure that 12 volts are present
on this
wire during cranking!

25. Install the 7.5 amp diode (supplied) in the field wire of the
alternator.
This is the smaller of the two wires, usually brown in color, that
plugs into
the alternator. Cut the wire and install the diode with the pink
crimp-on
connector facing toward the alternator. It is imperative that this
diode be in
the field circuit to protect the new electronics.

26. You may wish to install a new windshield washer bottle and bracket.
These
can be obtained through your local Jeep/Eagle dealer. Washer bottle
part
number is 55154744; bracket is 55026288.

27. Install the new air filter and bracket. It attaches to the
driver's side
body support rod. Connect the two 1/2" hoses, from the aluminum
connectors, to
the valve cover vent and the fuel cannister vent line.

28. OPTIONAL: If you wish to install a tachometer or an engine light,
the wires
for these are already in the harness, located close to the relays.
They will
be hanging out of the harness. The tachometer wire is light gray with
a yellow
stripe. This is the tachometer trigger wire. The O.E. 81-90 Jeep
tachometer
WILL NOT work with this system. The tach wire switches a 5V signal two
times
per engine revolution. Set your aftermarket tach on the 4-cylinder
scale to
achieve a true RPM reading. Some tachs will not work with this 5V
signal, or
they may have needle flutter at low RPM. If this is the case, you will
have to
splice into the coil negative side to operate your tach. If you hook
up to the
coil, use the 6-cylinder setting on your tach. The coil negative side
wire is
gray. (Hook up the tach last, after the engine is running, because some
tachs
have a low impedance and will short the coil to ground. This will not
harm
anything, but will prevent the engine from running.)

29. The "check engine light" wire runs directly to the PCM. The PCM
grounds
this wire to turn on a light to display fault codes. The light bulb
holders
are available at any local electronics supply.

30. On automatic transmission Jeeps, the brown wire that is coiled near
the PCM
connector must be connected to the neutral safety switch. This wire
can be
connected to the bottom of the starter relay, or to the center terminal
on the
neutral safety switch. On Chrysler automatics, this is the center
terminal.
If you choose to connect it to the starter relay, make sure that the
terminal
is for the neutral start switch. It should be grounded in park and
neutral.
This wire is for improved idle quality when in "Drive"

31. Reconnect the battery and turn on the ignition key. You should
hear the
electric fuel pump run for a few seconds and then shut off. Start the
engine
and IMMEDIATELY CHECK FOR FUEL LEAKS. Depending on the ambient
temperature,
the idle RPM may be high initially, and decrease as the engine warms
up. This
is normal!! Do not try to adjust the RPM by changing the opening of
the
throttle blade. Test Drive! Recheck all connectors and fuel lines!

32. Be sure to apply the CARB E.O. decal supplied in the kit in a
visible
location under the hood.


TROUBLE SHOOTING NOTES:
Hints we have found useful

1=2E This system is the same as used on the 1994 4.OL Wrangler. If you
need
service parts, or are checking fault codes, refer to the 1994 Jeep
Wrangler
Service Manual. The wiring is also the same as a 1994 Wrangler in
function and
color. You may call 1-800-626-1523 to order a service manual.

2=2E The crankshaft sensor is very sensitive. Make sure it is solidly
mounted.
Make sure that your engine does not have too much crankshaft end play.
The
paper button on the sensor will wear off with use of the engine.

3=2E The distributor should not be turned to change timing. It will not.
The
distributor is set to have the rotor tip .020' past #1 spark plug
terminal with
the engine at TDC.

4=2E The fuel return line to the tank must be unrestricted. Check this
carefully
before you hook up the return hose.

5=2E You may see fault codes for charging system too high or too low.
This is
normal and should be ignored.

6=2E The PCM does take some time (15 - 30 minutes) after first use to
"learn" the
best settings for your engine. You will notice better idle quality and
acceleration after this learning period. For this reason, the battery
should
be left connected if this vehicle is to be driven daily. If you use a
kill
switch, do not interrupt the B+ circuit or the PCM will need to
"re-learn"
every time you start the engine.


MANUAL TRANSMISSION
P5249610
MPI KIT
PACKING LIST

DESCRIPTION PART # QUA. DESCRIPTION PART#
QUA.

1) WIRING HARNESS P4532698 1 51) THROTTLE BODY
04856107 * 1
2) THERMOSTAT HOUSING 53006192 1 52) THROTTLE BODY GASKET
53007543 * 1
3) COOLANT SENSOR 33004281 1 53) 3/16' VACUUM CAP
9400049 * 1
4) INTAKE MANIFOLD 9400045* 1 54) FUEL LINE CLIP
34202997 * 1
5) FUEL INJECTOR CLIPS 04418257* 6 55) VACUUM PORT
53004523 * 1
6) FUEL INJECTOR 53030343* 6 56) SPEED SENSOR
56027015 * 1
7) FUEL INJ LINE-INLET 52018416 1 57) MAP SENSOR BRACKET
56027080 1
8) FUEL INJ LINE-RETURN52018417 1 58) 5/8"X7/8" SPEEDO ADAPT
9400012 * 1
9) FUEL PRESSURE REG 53030001* 1 59) 1/2" PCV HOSE
9400048 2
10) FUEL RAIL ASSEMBLY 53030435 1 60) 1/2" PLASTIC HOSE SPLC
9400016 2
11) THROTTLE CABLE 52079382 1 61) 3/16" TUBE X 1/4" NPT
9400018 * 1
12) THROTTLE CABLE BRCKT 53007486* 1 62) #10 X 1/2" SHEET METAL
SCREW 9400020 4
13) COIL BRKT & FUEL PMP PLATE P4532710 1 63) 1/4" TUBE X 1/4" NPT
9400019 * 2
14) IGNITION COIL 04797293 1 64) M5 X 20MM CAP SCREW
9400021 * 1
15) SPARKPLUG WIRE SET 83507178 1 65) 1/4" NC X 1-1/4" CAP
SCREW 9400025 2
16) OXYGEN SENSOR 56028301 1 67) 1/4" NC X 1 l/2" CAP
SCREW 9400022* 1
17) CRANK SENSOR 56026884* 1 68) M6 X 20MM CAP SCREW
9400023 * 4
18) THROTTLE BODY ELBOW 53006289 1 69) M8 X 20MM CAP SCREW
9400024 * 1
19) THROTTLE BODY CLAMP 53008274 2 70) 5/16" X 1" CAP SCREW
9400030 * 1
20) FUEL PUMP-ELECTRIC P4532709 1 71) M5 FLAT WASHERS
9400027 * 3
21) FUEL FILTER 33000076 1 72) M6 FLAT WASHERS
9400028 * 11
22) FUEL HOSE-18"X5/16" 9400047 1 73) 5/16" FENDER WASHER
9400029 * 1
23) FUEL PUMP CLAMP MNT 9400009 1 74) 5/16"X1-1/4" CAP SCREW
9400030 * 1
24) HOSE CLAMPS 5/16" 9400002 9 75) M8 LOCK WASHER
9400031 * 1
25) INTAKE HOSE-CAT 18" X 2-3/4" 9400008 1 76) M5 HEX NUTS
9400032 * 2
26) AIR FILTER ADAPTER 9400007* 1 77) 1/4" NC NYLOC NUTS
9400034 * 2
27) K&N AIR FILTER 9400003 1 78) 5/16" NC NYLOC NUTS
9400035 *
28) CLAMP 2-3/4" WORM 9400013 2 79) 3/16" VACUUM HOSE
9400036 * 1
29) ADAPTER HOLDDOWN CLAMP 9400006 1 80) 2.5" ADEL CLMP (FUEL
FILTER) 9400037 1
30) INTAKE HOSE ADAPTER 9400005 1 81) 1/4" NC X 1" CAP SCREW
9400039 2
31) VENT TUBE 1/2" X 3/8" X 90' 9400010 2 82) 3/16" FLAT WASHER
9400040 2
32) CRANK SENSOR BRACKET 9400004* 1 83) 1/4" FLAT WASHER
9400041 3
33) MAT SENSOR 33004280* 1 84) CONCAVE EXPANSION CUP
9400042 1
34) MAP SENSOR 33000153 1 85) INSTALLATION INSTRUCTS
9400043 1
35) FUEL CANNISTER 53030500 1 86) DIODE SPLICE
9400044 1
36) TIE WRAPS 4" 9400014 1 87) #10 X 2" SHEETMETAL
SCREWS 9400015 3
37) THERMOSTAT 4494469 1 88) VACUUM TUBE
53006237 1
38) DISTRIBUTOR 9400046 1 89) UNDER HOOD EMISSION DECAL
9400050
39) M6 X 14M CAP SCREW 9400052 7 90) 3/8" MOUNTING CLAMP
9400054
40) VALVECOVER FITTING (GRAY) 5303G497 1
41) VALVECOVER FITTING (BLACK) 53030495 1
42) VACUUM TUBING 53030728 1
43) BRACKET-FUEL CANNISTER 53009759 1
44) VACUUM TUBE 53006226 1
45) VACUUM TUBE 53030473 1
46) VACUUM TUBE 53030474 1
47) ECM MANUAL TRANSMISSION P4532679 1
48) M5 X 30M CAP SCREW 9400011* 2
49) FUEL PRESS. REG. CLAMP 04418897* 1
50) INTAKE MANIFOLD GASKET J3242855 1

* DENOTES PARTS THAT ARE IN PRE-ASSEMBLED UNITS



Getting rid of the EFI is the idea, not keeping it.

This EFI is designed for one specific engine as outlined in the text.
If you put the 4 liter head on the 258 lower what you get is not that
engine.

An aftermarket EFI controller using a Ford MAF sensor AND a MAP sensor
AND providing RS-232 link to a laptop is way, way, way better. There
was a good article in Grassroots motorsports magazine addressing this.

Of course plugging the injector holes and putting a propane mixer on
there works too.

I added the Electronic Fuel injection in case he came to his
senses. I realize common sense is not one of your forte
God Bless America, Bill O|||||||O
http://www.billhughes.com/

Bret Ludwig wrote:?
>
> As is so often the case we fail the reading Comprehension Test.

L=2EW. Hughes III (=DFill) wrote:
> I added the Electronic Fuel injection in case he came to his
> senses. I realize common sense is not one of your forte
> God Bless America, Bill O|||||||O

Fuel injection systems aren't Mopar's forte, to judge from the factory
kit.

If you are willing to trust some glue to hold all the coolant in, then
it might be a good thing. You can use the 4.2 intake, but the exhaust
manifold has to be 4.0.

All these guys that do any mods to the 4.2 like that head job or the FI
job all claim this big HP increase. Well... you get the same increase
they are crowing about for free by just killing the emissions computer
on the 82's to 91's, which by the way they have to do anyway for the
mods... LOL!

The rpm 'red line' goes from about 3300 rpm to 4400 and you get at least
a 10 mph increase in each gear.

My 86 CJ7 will just light up my 33's off the start if I punch it, it
then hits about 52 mph in 2nd at 4400 rpm, 3rd pulls hard up to 75 mph,
4th buries the speedo and I have no urge to find out how fast 5th will
go...

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Steve G wrote:
>
> Ive been reading about the 4.0 head swap for 4.2 motors. Is this really as
> good as it sounds or are there more headaches to be found?
>
> What all has to be replaced besides the head?
>
> Have to be fuel injected then?
>
> 40hp gain? really?

With my header and carb setup I've had NO problems keeping up with 4.0L's. I
still have an HEI that I will install.


"Mike Romain" > wrote in message
...
> If you are willing to trust some glue to hold all the coolant in, then
> it might be a good thing. You can use the 4.2 intake, but the exhaust
> manifold has to be 4.0.
>
> All these guys that do any mods to the 4.2 like that head job or the FI
> job all claim this big HP increase. Well... you get the same increase
> they are crowing about for free by just killing the emissions computer
> on the 82's to 91's, which by the way they have to do anyway for the
> mods... LOL!
>
> The rpm 'red line' goes from about 3300 rpm to 4400 and you get at least
> a 10 mph increase in each gear.
>
> My 86 CJ7 will just light up my 33's off the start if I punch it, it
> then hits about 52 mph in 2nd at 4400 rpm, 3rd pulls hard up to 75 mph,
> 4th buries the speedo and I have no urge to find out how fast 5th will
> go...
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
>
> Steve G wrote:
>>
>> Ive been reading about the 4.0 head swap for 4.2 motors. Is this really
>> as
>> good as it sounds or are there more headaches to be found?
>>
>> What all has to be replaced besides the head?
>>
>> Have to be fuel injected then?
>>
>> 40hp gain? really?

Yes, it's as good as it sounds.

You might need to change the manifolds, but I'm not sure. If your 258 is an
old one, like mine, it would be stupid to put on a 4.0 head and NOT change
both manifolds. My motor had the old style manifolds that had 6 into 1
collectors, these are very inefficient. You want the intake manifold that
has a large block under the carb/throttle body with long tubes running to
each intake port; the long tube that runs the length of the motor with short
tubes to the various intake ports doesn't work nearly as well. The exhaust
manifold has the same breathing problems and the intake manifold, but going
the other way; you want change from the 6 into 1 manifold to one that is 6
into 2 into 1, or some variation that makes tubes that can hold the entire
contents of the cylinders before coming to a restriction.

The 4.0 head doesn't have to be fuel injected, but if you use fuel injection
or a carb is important when selecting the intake manifold to use.

Before you bolt the 4.0 head down, you need to look at how the water galleys
line up between the head and the block. There are (I think) two water
galleys on the head that are exposed to the outside, and these need to be
blocked off with JB Weld, or something like that. This is an easy job, and
should NOT cause you to pass on doing the upgrade.





"Steve G" > wrote in message
...
> Ive been reading about the 4.0 head swap for 4.2 motors. Is this really as
> good as it sounds or are there more headaches to be found?
>
> What all has to be replaced besides the head?
>
> Have to be fuel injected then?
>
> 40hp gain? really?
>
>
>