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4.0L Engine revisions *********

'87-'90: 177hp at 4500rpm, 224lbft at 2400rpm, redline 5000rpm
The '87-'90 engines had Renix electronic multipoint fuel injection, electronic ignition, a 52mm throttle body, and an inefficient "low port" cylinder head similar to the old 4.2L/258. They have a water temp port in the back of the head. (Use a '91-'95 HO head for a head swap to replace these most easily.)

'91-'95: 190hp at 4750rpm, 225lbft at 3950rpm, redline 5250rpm
In 1991 engines received Chrysler sequential MPFI, a larger 60mm throttle body, revised intake and exhaust manifolds, and a more efficient high port cylinder head. As a result, these engines produced 13hp more than their predecessors and gained the "High Output" designation.

'96-'99: 190hp at 4600rpm, 225lbft at 3000rpm, redline 5300rpm
In 1996 engines received noise, vibration, and harshness fixes. The blocks were stiffened with extra ribbing, a main bearing brace was added, and lighter cast aluminium pistons were introduced to improve efficiency and reduce cold start piston slap. Engines also received revised camshaft timing for more low rev torque. Heads are similar except that they have no water temp port. (The OBD II system drives the guages and, only requires one port, these can be drilled and tapped for the sender used in earlier models if you're doing a head swap.)

'99.5-'01: 193hp at 4600rpm, 231lbft at 3000rpm, redline 5300rpm
In 2000 a distributorless coil-on-plug ignition system was installed, intake and exhaust manifolds were revised, and a more efficient water pump was included. These heads are quite different. They have smaller exhaust ports and, mounting bosses for the coil pack used with the distributorless ignition. There are different accessory mounting hole locations on these as well.

Injectors *********

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, ...Dark Tan, ...39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'99-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/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 19lb/hr @ 43.5psi (ACC-150819)
Accel 24lb/hr @ 43.5psi (ACC-150824)
Accel 26lb/hr @ 43.5psi (ACC-150826)
Accel 30lb/hr @ 43.5psi (ACC-150830)

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. The valve head diameter is 1.91" intake, 1.50" exhaust.

Cylinder head flow figures (cfm) at 25inH2O pressure drop are:

Non-HO head
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

HO head
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 with 2.02/1.60 valves
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

Head gaskets *********

The compressed thicknesses of the following gaskets for the 4.0 engine are:

Stock 4.0 '87-'90 #33004447, '91-'93 #33007143, '94-'95 #53020219, '96-'99 #53020754----0.052"
Mopar Performance #P4529242----0.041"
Victor-Reinz (Dana) #5713----0.045"
Detroit Gasket #67-1045----0.050"
SCE Pro-Copper #67-9035----0.050", #67-9034----0.043", #67-9033----0.032"
Fel-Pro #9076PT----0.052"

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-'01 #4798329----1.601" 13.3cc
Keith-Black Silvolite hypereutectic #2228----1.581" 11.5cc
Sealed Power hypereutectic H802CP----1.592" ~16cc

Stock Cam Specs *********

The stock Jeep 4.0 camshaft is a dual pattern cam with an advertised duration of 253.3/259.0 degrees intake/exhaust. Here are all the cam specs:

Duration: 253.3/259.0 degrees
Cam lobe lift: 0.265"
Rocker arm ratio: 1.6
Valve lift: 0.424"
Lobe separation angle: 107.3 degrees
Intake centerline angle: 114.3 degrees
Valve overlap: 41.6 degrees
IVO: 12.4 degrees BTDC
IVC: 60.9 degrees ABDC
EVO: 49.8 degrees BBDC
EVC: 29.2 degrees ATDC

Aftermarket camshafts *********

Crane Cams
Crower Cams
Isky Cams
Clifford Performance
Mopar Performance
Erson Cams

1,234 Posts
for some reason the 97-99 cherokee had 300hp in venezuela..i have a magazine that says that...if i find it i will scan it and post it

84 Posts
for some reason the 97-99 cherokee had 300hp in venezuela..i have a magazine that says that...if i find it i will scan it and post it
i'de give a left nut for one with that much power
and a good chuck of change for a tranny to hold up to it

934 Posts
I'd like to see an ad on a 300 hp stock cherokee...I've never heard of that in all of my XJ experience...
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