Courtesy of Dino at http://jeep4.0performance.4mg.com/tech_specs.html
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-'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)
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
1996-98......0630
1999-04......0331
Cylinder head flow figures (cfm) at 25inH2O pressure drop are:
Non-HO head #2686
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
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
HO head #0331
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 114.0 165.0 194.0 199.0 205.0
Exhaust flow....94.0 117.0 126.0 130.0 133.0
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
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-'98 0630 heads are almost identical except that they don't have a port for the coolant temp. gauge sending unit. The '99 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. Jeep recognised this and increased the exhaust valve opening duration on the '99 and later cam to compensate for the poorer exhaust port flow of the 0331 head.
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 thicknesses of the following gaskets for the 4.0 engine are:
Stock 4.0 (all years) #53020754AB----0.051"
Mopar Performance #P4529242/Victor Reinz Dana #5713----0.043"
Corteco #20667CS '87-'95, #20871 '96-'05 ----0.051"
Fel-Pro #9076PT1----0.051"
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-'04 #4798329----1.601" 13.1cc
Keith-Black Silvolite hypereutectic 2229----1.581" 11.5cc
Speed Pro hypereutectic H825CP----1.592" 15.8cc
Speed Pro cast aluminium 677P/677CP----1.585" 17.5cc
Intake manifold
The '91-'95 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", with a cross sectional area of 2.234 sq. in. The distance from the intake valve to the port opening is 9cm (3.5"), making the total distance 33cm (13") from the manifold plenum wall to the intake valve.
For a given intake manifold design, the cross-sectional area of the runner affects the location of an engine's torque peak in the RPM band. The runner length also has an effect, but not as much. According to this formula:
Peak Torque RPM = [Intake Runner Area (sq. in) X 88200] / Cylinder Volume (cu. in.)
Substituting 40.25 for the cylinder volume and 2.234 for the intake runner area, the result is that the runner area is tuned for a peak torque at 4900rpm. That's close to peak HP rpm on the 4.0 engine.
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. That's also close to peak horsepower rpm.
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.
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-'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)
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
1996-98......0630
1999-04......0331
Cylinder head flow figures (cfm) at 25inH2O pressure drop are:
Non-HO head #2686
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
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
HO head #0331
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 114.0 165.0 194.0 199.0 205.0
Exhaust flow....94.0 117.0 126.0 130.0 133.0
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
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-'98 0630 heads are almost identical except that they don't have a port for the coolant temp. gauge sending unit. The '99 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. Jeep recognised this and increased the exhaust valve opening duration on the '99 and later cam to compensate for the poorer exhaust port flow of the 0331 head.
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 thicknesses of the following gaskets for the 4.0 engine are:
Stock 4.0 (all years) #53020754AB----0.051"
Mopar Performance #P4529242/Victor Reinz Dana #5713----0.043"
Corteco #20667CS '87-'95, #20871 '96-'05 ----0.051"
Fel-Pro #9076PT1----0.051"
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-'04 #4798329----1.601" 13.1cc
Keith-Black Silvolite hypereutectic 2229----1.581" 11.5cc
Speed Pro hypereutectic H825CP----1.592" 15.8cc
Speed Pro cast aluminium 677P/677CP----1.585" 17.5cc
Intake manifold
The '91-'95 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", with a cross sectional area of 2.234 sq. in. The distance from the intake valve to the port opening is 9cm (3.5"), making the total distance 33cm (13") from the manifold plenum wall to the intake valve.
For a given intake manifold design, the cross-sectional area of the runner affects the location of an engine's torque peak in the RPM band. The runner length also has an effect, but not as much. According to this formula:
Peak Torque RPM = [Intake Runner Area (sq. in) X 88200] / Cylinder Volume (cu. in.)
Substituting 40.25 for the cylinder volume and 2.234 for the intake runner area, the result is that the runner area is tuned for a peak torque at 4900rpm. That's close to peak HP rpm on the 4.0 engine.
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. That's also close to peak horsepower rpm.
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.