Tech Specs
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Injectors

Some of those specs that are hard to find in any workshop manual.

The following is a list of the injectors used on the 4.0L since 1987 along with their rated static flow:

Model Year, ...Part #, ...........Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, .........Black, ...........39psi, .................18.6lb/hr
'91-'93, ........33007127, .........Brown, ..........39psi, .................21.0lb/hr
'94-'95, ........53030343, .........Tan, ...............39psi, .................21.0lb/hr
'96-'98, ........53030778, .........Grey, .............49psi, .................23.2lb/hr
'99-'04, ........04854181, .........Blue tip, ........49psi, .................22.5lb/hr
'05-'06, ........53013690AA, ...Brown tip, .....58psi, ................25.4?lb/hr

The injector flow rate varies as the square root of the pressure drop across the injector. The stock '91-'95 4.0 injectors are rated at 22lb/hr @ 43psi fuel pressure, so at 39psi they flow ( sq. rt.(39/43) x 22.0 = 21.0 ).
For stock/modified 4.0 engines or stroker build-ups the following injectors can be installed. The flow rates are:

Ford Motorsport 19.0lb/hr @ 39psi (Part no. FMS-M9593-C302)
Ford Motorsport 24.0lb/hr @ 39psi (Part no. FMS-M9593-A302)
Ford Motorsport 30.0lb/hr @ 39psi (Part no. FMS-M9593-B302)
Chevy LT1 24.0lb/hr @ 43.5psi (Part no. 17124248)
Chevy LT4 28.0lb/hr @ 43.5psi (Part no. 17124251)
'98 Chevy LS1 25.2lb/hr @ 58.0psi (Part no. 12533952)
'99-'00 Chevy LS1 26.2lb/hr @ 58.0psi (Part no. 12456154)
'01-'02 Chevy LS1/LS6 28.6lb/hr @ 58.0psi (Part no. 12482704)
Accel 19.2lb/hr @ 44.1psi (ACC-150119)
Accel 21.1lb/hr @ 44.1psi (ACC-150121)
Accel 24.4lb/hr @ 44.1psi (ACC-150124)
Accel 25.6lb/hr @ 44.1psi (ACC-150126)
Accel 29.4lb/hr @ 44.1psi (ACC-150130)

The '95 Jeep 5.2 ZJ/Dodge 5.9 injectors (Part no. 53030262) are rated to flow 24.6lb/hr at 39psi.

The selection of injector size will depend on the estimated horsepower output, brake specific fuel consumption BSFC (assume 0.5), no. of cylinders, and the injector duty cycle (assume 80% or 0.8). The formula is:

Injector size (lb/hr) = (horsepower x 0.5)/(no.of cylinders x 0.8)

Cylinder head

The stock cylinder head is cast iron and weighs 60lb. The valve head diameter is 1.91" intake/1.50" exhaust. Casting numbers are as follows:

Year............Casting No
1987-90......2686
1991-95......7120
1996-99......0630
2000-01......0331

Cylinder head flow figures (cfm) at 28inH2O pressure drop are:

Non-HO head #2686 (Courtesy of Greg Friedman)

Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 122.0 168.0 186.0 189.0 192.0
Exhaust flow....88.0 114.0 130.0 134.0 138.0

Ported non-HO head #2686

Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 124.0 183.0 197.0 207.0 216.0
Exhaust flow....87.0 113.0 138.0 153.0 159.0

HO head #7120 & #0630 (Courtesy of John Brown)

Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 66.0 128.0 179.0 206.0 209.0 209.0
Exhaust flow. 55.0 100.0 120.0 136.0 141.0 141.2

Ported HO head #7120

Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 68.4 132.6 185.4 213.4 216.5 216.5
Exhaust flow. 64.3 116.9 149.6 158.9 164.8 165.0

HO head #0331

Valve lift (in)..... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow..... 59.4 122.6 171.1 201.1 214.3 218.4
Exhaust flow...47.1   93.4 123.3 140.9 147.0 149.7

Ported HO head #0331

Valve lift (in)..... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow..... 65.2 128.4 186.5 219.5 218.9 224.8
Exhaust flow...56.9   96.9 123.9 140.2 148.9 153.2

Ported big valve 2.02/1.60 HO head

Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5
Intake flow.... 73.9 142.4 197.8 229.8 247.0
Exhaust flow. 65.3 114.0 135.9 146.3 157.1

Hesco aluminium 1.91/1.50 head

Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5
Intake flow.... 74.0 134.0 183.0 226.0 255.0
Exhaust flow. 55.0  93.0 117.0 131.0 142.0

The early '87-'90 non-HO heads have low intake ports that flow rather poorly. The later HO heads have higher intake ports that flow more air by allowing a straighter shot into the cylinders. The '91-'95 HO heads with casting no.7120 have the highest intake and exhaust port airflows, especially at lower valve lifts where it is most important, and are the best for performance. The '96-'99 0630 heads are almost identical except that they don't have a port for the coolant temp. gauge sending unit. The '00 and later HO heads with casting no.0331 have smaller exhaust ports to produce a faster warm-up of the catalytic converter and improve emissions, but performance also suffers because the ports don't flow as well as those of the 7120 and 0630 castings.
The exhaust ports flow relatively poorly compared to the intake ports on all the 4.0 heads so this engine would perform better with a dual pattern cam that has more exhaust valve opening duration and lift than the intake.
The intake ports of the HO head are rectangular and measure 1.625" x 1.375", while the exhaust ports are elliptical and measure only 1.375" x 1.250". The port cross-sectional areas are 2.234 and 1.350 sq. inches respectively. For good street performance, it is recommended that the port c/s area should be about 85% of the valve head area. Therefore it should be 2.435 sq. in. for the intake ports and 1.502 sq. in. for the exhaust ports. The stock port c/s areas therefore need to be enlarged by 9.0% for the intake and 11.3% for the exhaust. The ports should be matched to the intake and exhaust manifold runners to smoothen airflow and prevent power-robbing turbulence.
For those who would like to undertake a DIY head porting job, the Standard Abrasives DIY Head Porting Guide is a must read.

Head gaskets

The compressed thickness of the latest stock 53010587AA / Mopar Performance P4529242 / Victor Reinz 54249 multi-layer steel gaskets is 0.043" (1.1mm)

Pistons

The pin heights and dish volumes of pistons available for the 4.0 engine are:

Stock 4.0 cast aluminium '87-'93 #83500251, '94-'95 #4773157, '96-'06 #4798329----1.601" 13.1cc
Keith-Black Silvolite (UEM) cast aluminium 2229/2229c----1.581" 11.0cc
Keith-Black Silvolite (UEM) hypereutectic 3241hc/3242hc----1.592" 13.7cc
Sealed Power (Sterling) cast aluminium 677P/677CP----1.585" 17.5cc
Sealed Power (Sterling) hypereutectic H802CP/H825CP----1.592" 15.1cc
Keith-Black Silvolite (UEM) forged stroker IC944----1.353" 21.0cc NEW
Keith-Black Silvolite (UEM) forged stroker IC945----1.353" 10.8cc NEW

Intake manifold

The '91-'99 intake manifold is aluminium and has equal length 24cm (9.5") long runners. The runners are rectangular with internal dimensions of 1.625" x 1.375" and a cross sectional area of 2.234 sq. in. (14.4 sq. cm). The '00-'06 intake manifold has smaller diameter curved runners with internal dimensions of 1.53" x 1.26" and a cross sectional area of 1.928 sq. in. (12.4 sq. cm), and is clearly designed to produce more torque at lower rpm. The distance from the intake valve to the port opening is 3.5" (9cm), making the total distance 13" (33cm) from the manifold plenum wall to the intake valve.
For a given intake manifold design, the cross-sectional area of the runner and the runner length affect the location of an engine's torque peak in the RPM band. According to the Helmholtz tuning model and the formula shown here, the intake runner area and length are tuned to resonate and produce an inertial supercharging effect at 5000rpm for the '91-'99 engine and 4650rpm for the '00-'06 engine. That's very close to peak horsepower rpm for all High Output 4.0L engines.

Exhaust manifold

The same design principles for the intake manifold also apply to the exhaust manifold. The cross-sectional area of the primary header pipe affects the location of an engine's torque peak in the RPM band. The pipe length generally will not change the peak torque or the RPM at which it occurs. A length change has the effect of improving the torque on only one side of the peak by "borrowing" it from the other side. A shorter pipe improves torque after the peak (reduces it at lower RPM), preventing the torque curve from falling off so quickly as speed increases. A longer pipe extends the torque curve backwards to improve the engine's flexibility, at the expense of after-peak torque.
The stock exhaust manifold and the Borla header have a primary pipe internal diameter of 1.375" and a cross sectional area of 1.49 sq. in. Using this formula:

Peak Torque RPM = [Primary Pipe Area (sq. in) X 88200] / Cylinder Volume (cu. in.)

the stock exhaust manifold and the Borla header are tuned to a peak torque of 3265rpm. That's right at the peak torque rpm of the 4.0 engine.

Block Casting Numbers

Year............Casting No. ...........................Part No.
1987...........53005535 (8933002665)....83503400
1988-90.....53005535 (8933002665)....83505110
1991...........53008405..............................4626155
1992...........53008405..............................4638959
1993...........53008405..............................4728988
1994-95......53008405.............................4778882
1996-99......53020569.............................4883025
2000-01......53010449AA.......................5013166AB

Crankshaft Casting Numbers

The stock Jeep 4.0 crankshaft is nodular iron, has 8 counterweights, and weighs 55lb.

Year............Casting No.........Part No.
1987-90......3003453..........83503409
1991............3003453..........83507107
1992............3003453...........4638952
1993-95......3003453...........4728882
1996............53020767.........4728882
1997-99......53020767.........4864726
2000-01......53010411.........4864726AB

Connecting Rod Casting Numbers

Stock Jeep 4.0 rods are cast iron, 6.125" long from center to center, and weigh 660g. The casting no. is 53020126 for all years.

Pushrods

Stock pushrods are oil-through type with pressed-in balls at each end. They are 5/16" in diameter and 9.625" long

Pilot Bearings

The 5-speed manual transmission is the light-duty Peugeot BA10/5 in the '87-'89.5 4.0 XJ, the medium duty Aisin-Warner AX15 in the '89.5-'99 4.0 XJ, and the medium-duty New Venture Gear NVG3550 in the '00-'01 4.0 XJ. When carrying out engine swaps (either another 4.0 or a stroker), selection of the correct pilot bearing can be a headache. The details below will make choosing a pilot bearing simple:

'87-'89.5 BA10/5:

OEM pilot bearing 33004041 for '87-'91 4.0 engine
Advance Adapters pilot bushing 716120 for '92-'06 4.0 engine
*Upgrade transmission to AX15 or NVG3550 for stroker engine swap*

'89.5-'91 AX15:

OEM pilot bearing 33004041 for '87-'91 4.0 engine or stroker
Advance Adapters pilot bushing 716120 for '92-'06 4.0 engine

'92-'99 AX15 and NVG3550:

OEM pilot bearing 53009180AB for '87-'91 engine or stroker
OEM pilot bearing 53009180AB or 53009181 for '92-'06 4.0 engine.

Stock Cam Specs

The stock '87-'95 Jeep 4.0 camshaft is a single pattern cam with the following specs:

Advertised duration int./exh.: 270/270 deg
Duration @ 0.050" lift int./exh.: 197/197 deg
Valve lift int./exh.: 0.424"/0.424"
Lobe separation angle: 112 deg
Intake centerline angle: 120 deg
Valve overlap (advertised): 46 deg
IVO: 21.5 deg ATDC (0.050" lift)
IVC: 38.5 deg ABDC
EVO: 22.5 deg BBDC
EVC: 5.5 deg BTDC

The stock '96 and later Jeep 4.0 camshaft is a dual pattern cam that produces more torque at lower rpm and a wider torque spread. The specs are as follows:

Advertised duration int./exh.: 253/259 deg
Duration @ 0.050" lift int./exh.: 188/192 deg
Valve lift int./exh.: 0.408"/0.414"
Lobe separation angle: 107 deg
Intake centerline angle: 114 deg
Valve overlap (advertised): 43 deg
IVO: 20 deg ATDC (0.050" lift)
IVC: 28 deg ABDC
EVO: 16 deg BBDC
EVC: 4 deg BTDC

This webpage shows all the specs of stock and popular aftermarket cams for the 4.0 engine. Since the exhaust ports of the stock 4.0 head flow relatively poorly, the 4.0 engine responds very well to a dual pattern cam with a longer exhaust valve opening duration and lift.

Aftermarket camshafts

Clifford Performance
CompCams
Crower Cams
Erson Cams
Hesco
Isky Cams
Lunati Voodoo Cams
Mopar Performance
505 Performance