130 MOPAR PERFORMANCE PARTS INTRODUCTION The Jeep

130
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MOPAR PERFORMANCE PARTS
Block
INTRODUCTION
Flywheel Attaching Package
The Jeep 4.0L Power Tech engine is a cast iron, In-Line 6
cylinder design. The cylinder block is drilled forming
galleys for both oil and coolant. It has a standard bore and
stroke of 98.4 x 87.4 mm (3.88 x 3.44").
Bolts required to attach flywheel and clutch to new engine
assembly. Includes 6 flywheel bolts, 6 clutch bolts, and a
pilot bearing.
The 4.0L has a liquid cooled, forced circulation cooling
system with a capacity of 11.4L (12 quarts).
Torque Converter Drive Plate
The cylinders are numbered 1 through 6 from front to rear.
The firing order is 1-5-3-6-2-4 (Figure 4-1).
The crankshaft rotation is clockwise, when viewed from the
front of the engine. The crankshaft rotates within seven
main bearings. The camshaft rotates within four bearings.
For more information, refer to 4.0L Engine Specijications,
'Engine Assembly' section of this chapter.
P4529247
Flywheel attaching package.
The torque converter drive plate connects the crankshaft
to the torque converter and also carries the starter ring
gear. For 4.0L engine only. Not SFI approved.
P4529248
Torque converter drive plate.
Drive Plate Attaching Package
Bolts required to attach torque converter drive plate to the
crankshaft and to attach the torque converter to the drive
plate. Includes 6 flywheel bolts and 4 torque converter bolts.
P4529249
Drive plate attaching package.
Build Date Code
The engine Build Date Code is located on the machined
surface on the right side of the cylinder block between the
No. 2 and No. 3 cylinders (Figure 4-2).
The digits of the code identify:
FIRING ORDER
1. 1st digit-the year (e.& 4 = 1994).
1 . 5 3 6 2 4
Uw(WIsE
2.
ROTATION
J-D-7
Figure 4
-1
Engine Block Hardware Package
Includes cam bearings, various freezelcore plugs and
locating pins. For use when block is tankedstress relieved
and machined. For 1987-89 4.0L engines only.
P4529673
Engine block hardware package.
Engine Teardown Gasket Set
Designed for bearing check, bore check, or cylinder head
modifications/teardown only. Gaskets include: cylinder
head, oil pan, intake/exhaust manifold and front cover
gaskets. For 4.0L engine only.
P4529245
Engine teardown gasket set.
2nd and 3rd digits-the month (01-12).
3. 4th and 5th digits-the engine type/fuel
systedcompression ratio (MX = a 4.0L 8.7:l
compression ratio engine with multi-point fuel
injection system).
4.
6th and 7th digits- the day of the month of engine
build (01-31).
Example: Code "401MX12" identifies a 4.0L engine with
a multi-point fuel injection system, 8.7:l compression ratio,
built on January 12, 1994.
4.0L POWER TECH IN-LINE 6 (BLOCK)
131
Block Hardness
With any cast iron block, there is a relationship between
hardness and strength. The harder it is, the stronger it is. The
assumption is that a stronger block can make more power.
However, if the basic design of the block is weak, then it
will break frequently. Standard production blocks are not
designed as strongly as “race” blocks. So if you double or
triple the power output of a standard production engine with
high performance parts, you will have problems.
We know that hard blocks don’t break and soft ones do.
Racers therefore want hard blocks. If you add a strong
design to a hard material, you will have a race block. This
means that the block will last longer and make more power
for longer periods of time. Chrysler-Plymouth-Dodge-Jeep
has always used a high nickel material in its cast iron
blocks. This makes them harder.
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Figure 4 2
Oversize and Undersize Component Codes
Rough Bored Blocks
Some engines may be built with oversize or undersize
components such as:
0
Oversize cylinder bores
0
Oversize camshaft bearing bores
0
Undersize crankshaft main bearing journals
0
Undersize connecting rod journals
These engines are identified by a letter code (Figure 4-3)
stamped on a boss between the ignition coil and the distributor.
Rough bored blocks have the cylinder bores roughed-in but
not finished-the surface finish on the bore is rough but
machined. That means that each cylinder must be
bored-to-size and then honed. The bore-to-size operation is
referred to as the finish bore. As an engine builder, you
must leave enough material on the finish bore operation to
allow for the finish hone to size the bore correctly.
The advantage of rough bored blocks is you have a greater
selection of bore sizes available to you. Most race engine
builders DO NOT want a production hone, so why pay
extra for it if you are going to change the bore size? By
omitting the finish bore and honing operations, the block
can be purchased for less money.
CYLINDER BLOCK PREPARATION
The first step in preparing the block for all-out racing is to
stress-relieve it (typically not required for new race blocks
or many used blocks). For more details, refer to StressRelieving, in this section.
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Figure 4 - 3
After the block has been stress-relieved, new camshaft
bearings and core plugs should be installed. The old main cap
bolts should be thrown away. The block should be re-honed
and the deck flatness checked. A light cut should be taken if
it is not perfectly flat. The main bearing bores will also have
to be checked and align-bored or align-honed if out of
alignment. New camshaft bearings will also be required.
Block-to-Head Distortion
(Refer to Head Distortion, ‘Cylinder Head’ section of
this chapter.)
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MOPAR PERFORMANCE PARTS
Stress-Relieving
Note: The following is not required for thermally-cycled,
used engine blocks, except for align boring and honing,
which may be required on any new or used engine.
The first step in obtaining straight and round bores is to
select a stress-relieved block. Only 426 Hemi engine blocks
were stress-relieved in production. However, a block will
stress-relieve itself with use; that is, a used block has
already been stress-relieved (thermal cycles are the key).
Heating up and cooling down is the ideal cycle-again and
again and again, which means that an engine block used in
an around-town commuter vehicle is better than a block
used in a long-haul truck or police car, which is
infrequently shut off.
Blocks will also stress-relieve themselves in racing
applications. A block can be built into a race engine and run
several hundred times. It can then be rebuilt into a better
engine because the bores will be straighter and will move less
with use. The straighter the cylinder bore, the more power the
engine will make. Once you’ve got a good one, keep it.
Once the engine is disassembled, the first step in preparing
the block is to remove the main bearings caps, clean all
joining faces, reassemble and torque to specifications. The
stress-relieving process consists of heating the block and
main caps to 1050°F and holding at that temperature for
two hours. It should then be furnace cooled to 500°F at a
cooling rate not to exceed 2 0 0 ” h . The block can then be
air cooled to normal air temperature.
After the block has been stress-relieved by the ’oven’
method (not by thermal cycling), new camshaft bearings
and core plugs should be installed. The old main cap bolts
should be thrown away. The block should be re-honed and
the deck flatness checked and a light cut taken if it is not
flat. The main bearing bores will also have to be checked
and align-bored or honed if out of alignment. New camshaft
bearings will also be required.
Sonic Testing
If the block is to be used in serious racing applications, it
should be “Magna-checked” (sonic tested). With this
process, the thickness of the cylinder bore walls can be
checked nondestructively. This will indicate how good your
particular block is, or it will allow you to select the best
block of several available, if you have the option. It is
highly recommended that you have more than one block
tested so you don’t invest your time in a weak or “flexiblock.”
If YOU only have one block, the bore-wall thickness check
really only serves as base information and a general
Performance indicator. Write this measurement down and
keep it in your engine build-up file.
However, if you have several blocks to choose from, the
best engine will be the block with the least amount of core
shift (bores with the same thickness all the way around), or
the block with the core shift in the “major thrust” direction.
The major thrust direction is to the passenger side of the
cylinder bore as the block is installed in the vehicle.
Core Shift
It seems as though every racer you talk to uses the term
“core shift.” It’s used so frequently it seems to be the cause
of every engine problem in racing! Obviously, this isn’t
correct. Without making it too complicated, let’s look into
this subject a little closer.
First of all, to discuss core shift we must have a casting. It
can be of any material (aluminum, iron), but it has to be a
casting. Second, the casting must have a “core” in it. In an
over-simplified explanation, a “core” is used to cast an
internal passage in a casting. This internal passage could be
a water jacket in a head or block, or an intake runner in a
manifold. Not all castings use cores. Core shift is most
often discussed relative to cylinder blocks, so we’ll
concentrate on them. On any given part, there may be more
than one core. This varies from one manufacturer to
another. Cores are generally made of sand. The sand is held
together with a bonding agent.
The cylinder block is the largest casting that we make. The
main core in the block is the water jacket. In’this case, core
shift would occur if the water jacket core moved relative to
the main tooling. Since the water jacket core is set inside
the main tooling, it is possible for this core to be shifted in
position. In most cases, this shift is caused when the molten
metal hits the core and moves or offsetddeflects it.
The core could move up or down, fore or aft, but the
important direction is left or right. Left or right shifts move
the core in the major or minor thrust direction. This makes
the cylinder bore either thick or thin on the major thrust
side. Having the core shifted so that the major thrust side is
somewhat thicker is superior to being perfectly round.
Consequently, having the major thrust side too thin is NOT
desired. To find out if this has occurred, the block must be
sonic tested.
Most of the confusion relating to core shift occurs because
racers try to find a “quick” way to determine if a block has
core shift without sonic testing! Remember that not all core
shift is bad. Looking at the front or rear of the block will not
tell you if the block has core shift because you’re not
looking at the water jacket. The only way to see the water
jacket is too look down the holes in the top of the block.
These holes are quite small and don’t allow you to visually
judge for core shift.
So that brings us back at sonic testing. Sonic testing
measures the thickness of the cylinder bore in the major and
minor thrust directions. Technically speaking, all the bores
should have the material shifted in the same direction.
Surfacing ("Decking")
perhaps this topic would be more properly labeled
"resurfacing" because the block already has a deck surface.
Sometimes this operation is called "decking" the block. In
either case, the top surface of the block, called the deck, is
milled. This operation decreases the block's height.
Why would you "deck" (surface) the block? One possibility
is to increase the compression ratio. Another is to take
weight out of the block/engine assembly. Most engine
builders DO NOT feel the production machining to be
acceptable in the area of flatness. The engine builder may
want to remove the production tolerance of the decks.
Usually a race machine shop will machine the stock deck of
a new block .020" to .040". They will take very light cuts to
gain the desired specifications. If it is a used engine that has
seen a lot of heat, they may have to increase these numbers
to get it flat enough. In decking the block, the machine shop
must be very careful that it does not make the resulting deck
surface too smooth or the cylinder head gasket will not seal.
Let's look at an example. The 4.0L engine has a block
height of 9.45". A race engine builder may machine 0.020"
off the deck surface to gain flatness, which gives a final
block height of 9.43". Never make calculations based on
average numbers like the 9.45". Or, if you have to, leave
enough stock so that you can get exactly where you want to
without scrapping parts (.040" is preferred). What if the
crank has a stroke that is .01O" too long, or a connecting rod
that is .005"" too long, or a piston that is .005" too tall? It
wouldn't be the block that is wrong, but the block can fix
them all with no problem if we left our engine builder with
a .040" cushion.
1. Honing Plates
For a serious all-out race engine, the use of a honing
of a
plate is strongly recommended. It should be made
held on
1 to 1-1/2" thick steel plate. The honing plate is
the
by capscrews. The screws should be torqued to
same specifications as the standard head bolts.
Thickness of the honing plate and installation torque
an
are very important, but of equal importance (and
thread
item often overlooked) is the depth of in and
engagement. Bolts should be turned all the Way
then backed off one turn for proper thread depth.
2.
Why a Honing Plate?
're
At the beginning of the race season when you
.]ding a
rebuilding your tried-and-true race engine or bm
should
new engine for the upcoming season, the block
be honed using a honing plate. This is the only way to
throttle
make the bores straight and round with the
d at
wide open. If the bores aren't straight and roUn
flake
W.O.T. (wide open throttle), the engine Won F or
any horsepower. If you're building several engine&'
to get
plan to do so over the next few years, it will pay
builders
your own honing plate. Most people/engine
for
and machine shops don't have honing plates
Chrysler-Plymouth-Dodge-Jeep engines. Honing
plates don't wear out. Cast iron plates are less
expensive but can break if mishandled or dropped'
Billet steel plates are much stronger and more durable'
Honing
7t
Before the honing operation is started, the cylinder walls
should be inspected for cracks or pits and the bores checked
for taper and roundness. A cylinder bore is most accurately
measured using a dial-bore gauge. For the actual honing
operation, approximately .004" (.002" per side of material)
should have been left after boring. (The size of the piston
and the piston design are other factors determining the bore
size and the piston-to-wall clearance.) The hone used to
gain the desired surface finish is stipulated by the choice of
Piston rings, but regardless of the actual finish (perfectly
smooth or slightly rough), it should have a 45" cross-hatch
Pattern. '(Moly rings, 10-15 micro inches; chrome or
stainless steel, 15-25 micro inches. A 30 micro finish is
fairly rough and is close to the hone finish on a production
engine. A 5 micro finish is very smooth.) After honing, the
bores should be straight (no taper) and round within +.002".
Having a STRAIGHT bore that is ROUND with NO
TAPER is THE single most important step in building a
race engine that produces good horsepower, high rpm,
and/or high specific output.
3.
Honing Plate Thread Engagement
with
The honing plate should be held on to the block easy
the same thread length as the head. This sounds
e
enough, but how do you get the two to be th
trying to
Since cylinder head distortion is what you're
after
match, the first step starts with the hea are to
machining. The head bolts with washers, if theiYnserted
be used with the head on final assembly, are
out the
into the head and the length of bolt protrudinmthat this
bottom of the head is measured. We'll assume to be
measurement is .900". The bolts that are going late.
used with the honing plate are inserted into the
(T
134
MOPAR PERFORMANCE PARTS
The amount that sticks out of the bottom of the plate
has to be adjusted to .900". If the first pass yielded a
length of 1.200", then hardened washers can be
installed under the bolt head. Hardened washers run
around .100". So, in this example, three hardened
washers would be used to get the correct length. (For
more information refer to Block-to-Head Distortion,
'Cylinder Heads' section of this chapter.)
Boring and Milling Specifications
Because it is a thin wall casting design, the 4.0L can only
be over-bored .030" (maximum), although .020"
(maximum) is preferred. Regardless of the amount of
overbore, if the engine is to be used for high output racing
purposes, the cylinder wall thickness should be checked to
be sure the block doesn't have a bad case of core shift. The
cylinder wall thickness should be the same all the way
around or thicker on the major thrust side of the cylinder
bore; that is, passenger side (as installed in the vehicle).
1. When machining cylinder head and deck, be sure
they're perfectly flat.
2.
When milling cylinder head and deck, don't make
them too smooth or you could have gasket sealing
problems. A typical production surface (100 microinches) should be your guide.
7.
If cylinder bore taper does not exceed 0.025 mm
(0.001") and out-of-roundness does not exceed 0.025
mm (0.001"), the cylinder bore can be honed. If the
cylinder bore taper or out-of-round condition exceeds
these maximum limits, the cylinder must be bored and
then honed to accept an oversize piston. A slight
amount of taper always exists in the cylinder bore after
the engine has been in use for a period of time.
CYLINDER BLOCK ASSEMBLY
Head Bolts
All cylinder head bolts should be screwed into the block
without the cylinder head. Visually inspect the rows of bolts
for any that may be bent, or for bolts with holes drilled at
any angle, or for holes that are not drilled deep enough.
When the head bolts are screwed in, the depth of thread
engagement should be checked and recorded.
Note: It is recommended that new cylinder head bolts and
main cap bolts always be used (if possible) when rebuilding
an engine.
Bottoming Tap
The milling of the intake manifold gasket surface can be
done on the intake manifold itself instead of the head.
A bottoming tap should be run down all head and main
bearing bolt holes. The head bolt holes should be
chamfered slightly to prevent the top thread from pulling up
when the head bolts are torqued.
Cylinder Bore Measurement
Main Bearing Bores
1. It is mandatory to use a dial bore gauge to measure
each cylinder bore diameter (Figure 2-11). To correctly
select the proper size piston, a cylinder bore gauge
capable of reading in 0.003 mm (.OOOl'')
INCREMENTS is required. If a bore gauge is not
available, DO NOT use an inside micrometer.
Main bearing bores must be checked for both specified
diameter and alignment with each other. If either is off, an
align-boring machine should be used to align-bore the
block. A crankshaft-turning tight spot indicates bores are
out of alignment.
2. Measure the inside diameter of the cylinder bore at
three levels below top of bore. Start perpendicular
(across or at 90 degrees) to the axis of the crankshaft
and then take two additional readings.
3. Measure the cylinder bore diameter crosswise to the
cylinder block near the. top of the bore. Repeat the
measurement near the middle of the bore, then repeat
the measurement near the bottom of the bore.
4.
Determine taper by subtracting the smaller diameter
from the larger diameter.
5.
Rotate measuring device 90" and repeat steps above.
6.
Determine out-of-roundness by comparing the
difference between each measurement.
Deck Height
Once the main bearing bores are known to be in alignment,
the deck surface of the block should be checked to make sure
it is parallel with the axis of the crankshaft. The distance
from the centerline of the crankshaft to the deck surface of
the block should be exactly the same at the front and rear. If
not, the deck surface will have to be milled. At this time the
deck height can be machined to the proper dimension.
Note: Deck heights that are above the block surface will be
increased by milling the block. Check the engine's
blueprint specifications before milling. The resulting
machined surface of the deck must be on the rough side to.
produce a good gasket seal and prevent the head gasket
from moving.
Notching the Cylinder Bore for Connecting Rod
Clearance
If you are attempting to install a crankshaft from a 4%
engine into a 4.0L engine, you may have to notch the
bottom of the cylinder bores (as required) to obtain .100"
clearance (Figure 4-4).
There are many variables associated with this P0PUlar
modification (too numerous to go into detail hae). For
more information, call the Mopar Performance parts
Technical Assistance Hotline at 1-248-969-1690, Or fax
them at 1-248-969-3342. They'll be glad to help YOU.
Rod Notch at Bottom of Cylinder Bore
Dowel Pins
Ensure that all dowel pins used for aligning purposes are
the proper height (not too high), and that the dowel pins
locate the head properly so that combustion chambers are
properly centered over cylinder bores. Check to be sure that
the dowel pins don't hold the head up off the block.
Note: Check without a head gasket.
Rear Main Bearing Oil Seal
Cylinder Bore Notch for
-Top
The rear main,bearing oil seal machined groove should be
roughed slightly with a center punch and the rope seal must
be seated all the way in. The rubber rear main seal should
be held in place with Permatex (RTV) behind the seal.
Of
Block
Camshaft Bearings
When installing camshaft bearings, make sure that the oil
holes in the bearings line up with the oil holes in the block.
DO NOT replace the camshaft bearings unless they are bad
or the block has been tank cleaned in acid.
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Rod Notch at Bottom of Cylinder Bore
Bottom of
cylinder
Deburring
Use a small, fine file to remove burrs and break all sharp
edges in the main bearing bores and around the cylinder
bore chamfers, as well as other sharp edges on the block.
Figure 4 - 4
CC'ing the Block
Tappet Bores
The tappet bores may be shined with #400 paper to remove
rough spots or burrs. A brake cylinder hone may also
be used with care. Tappet bore clearance is very important.
If it is too tight, the lifters will stick. Use .0015" for flat
and over .0015" to .003" for rollers. High clearance
can cause low oil pressure if the tappet bores are "wet."
If a big, flat-tappet camshaft that requires .100" oversize
mushroom lifters is going to be used, the bottom of the
llfterbore should be spot-faced to a slightly larger diameter
than the diameter of the mushroom lifter bottom. A back
'pot-facing tool is required to do this.
ADDITIONAL CYLINDER BLOCK PREPARATloN
AND ASSEMBLY TIPS
136
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MOPAR PERFORMANCE PARTS
First, we strongly recommend that the engine builder read
completely this chapter before any engine work is started.
Before the engine is assembled, all the basic parts (block,
crankshaft, head, etc.) should be cleaned, and then cleaned
again! The bearing clearances should be checked with
Plastigauge (P4286819) or micrometers (inside and outside).
Before reassembling, gather all the chemical products
likely to be needed such as RTV,Loctite, etc. If any parts
are to be stored after they are machined and/or cleaned,
they should be sprayed with a rust preventive, wrapped in
newspaper and covered with plastic bags.
When the camshaft and lifters are installed, a camshaft
break-in oil should be used on the camshaft lobes and
journals and the outside of the lifters. The camshaft breakin oil should come with the camshaft kit. If you need
camshaft break-in oil, order Lubrizol.
Before totally disassembling the block, check the deck
height of the pistons. Deck height is the distance from the
top of the piston to the top of the deck surface of the block.
This is an important dimension since it has a direct influence
on compression ratio. If the piston is a flat-top type, it will
usually be below the deck and this is the distance that must
be measured. A domed piston will stick up above the deck
surface and the distance is measured from the deck to the
flat of the piston, not the top of the dome. Mark this figure
down for future reference and completely disassemble the
block. On a new block, wait until the block is bored to size
before measuring the deck height.
When all machine operations are complete, the block
should be thoroughly washed out with solvent. Use bottle
brushes of suitable size to clean out all bolt holes, oil
passages, etc. Finish off with another thorough washing,
using a good, common detergent and warm water. Blow or
wipe dry and oil to prevent rust. Engine parts can’t be too
clean. Many early engine failures can be traced to dirt or
foreign objects (metal chips, etc.) that were left in the
engine when it was reassembled.
Let’s assume your main caps are O.R. and you have them
all. We’ll also assume that you are building a race or high
output engine. The problem with main caps is that they are
too simple. If they look like the right caps and we have
enough, then we’ll probably use them even if they aren’t
from this particular block. We have already stepped Over
the line in this last sentence. We’ll explain shortly.
You may be asking, “If my caps aren’t broken and I have
enough, why should I change?’ or, “Why should I install new
caps?” These two questions are not the same! First, remember
that if the main caps are changed, then the block MUST
align-bored. Always! If you are building a race engine, you
also MUST align-bore the engine. (The only exception is if
the engine was align-bored on its last rebuild, then it should
be alright.) Remember our “over-the-line” sentence regarding
using caps that weren’t from our particular block? In this case
we must also align-bore the block.
Remember that a weak cap doesn’t necessarily fail itself.
An engine failure will more likely occur with the bearings,
crankshaft, bolts, or even the bulkhead. A cap failure would
only occur in the most extreme cases. But it does occur.
You’d like to find it when you are routinely checking the
bearings, but you don’t always get that lucky!
Note: It is recommended that new main cap bolts always
be used (if possible) when rebuilding an engine.
FREEZE PLUGS
Every block used in production uses freeze plugs. They are
pressed into the sides and ends of the block. If they do their
job correctly, you will probably never know they are there.
If they fail, things can go wrong very quickly.
MAIN CAPS
If you are building a race engine, it is highly recommended
that the block be thoroughly cleaned before you start. TO
clean a block thoroughly, you need to remove the freeze
plugs. If you have the block hot-tanked, then the freeze
plugs MUST be replaced because they have lost their
“press” and will fall out as soon as there is any pressure in
the water jacket.
Hardened Washer Sets
Freeze plugs can’t be re-used, so once you take them out,
you need a new set.
For use with head bolts and main cap bolts.
1
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1
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!
f
P4120456
Comprised of: (20) - 3/8“ washers.
I
P4120457
Comprised of (20) - 7/16” washers.
j
P4 120458
Comprised of: (20) - 1/2” washers.
We all know an engine must have a set of main caps to
function. If you have a used engine block, it probably has
its own main caps, but some blocks may have broken or lost
caps. Main caps should be replaced in sets. Most used
engine blocks should have the mains align bored before the
engine is assembled into a “race” engine.
1