Here you can find information regarding the assembly of the Dodge 4.0L SOHC engine. In this guide we will
start from the inside of the engine including the
crankshaft, connecting rods, and piston ring installation and then move outwards all the way to the pulley belt
system. Along the way correct procedures and torque specs
will be given to aid in the assembly of the engine. Feel free to start from the beggining and work your way
outwards or skip ahead to your current position in the engine for what you may need.
Crankshaft Main Caps Installation
The 4.0L engine block main bearing caps should be inspected for any defects or flaws before installation.
Be sure to lubricate the bearing surfaces prior to installation. Once prepared you can place the caps onto the crankshaft
and begin tightening the bolts down in a multi stage process. For the inner bolts you can start by torqueing them down to
15 ft-lbs and then follow it up with a 90 degree turn by going through each bolt during each step. The outer bolts can be
tightened down to 20 ft-lbs and then a 90 degree turn. The main bearing side bolts can be installed last and torqued down to 20 ft-lbs. Be sure to
go through each bolt during each step and work your way from the inside or middle caps to the outside or outwards bearing caps.
Once finished you should be good to continue with the rest of the engine.
Dodge Nitro 4.0L Main Cap Inner Bolts Torque Specs : 15 ft-lbs + 90°
Dodge Nitro 4.0L Main Cap Outer Bolts Torque Specs : 20 ft-lbs + 90°
Dodge Nitro 4.0L Main Cap Side Bolts Torque Specs : 20 ft-lbs
Piston and Connecting Rod Installation
To install the pistons and connecting rods you must first install the piston rings into each piston. Be careful
not to stretch the rings or break them during installation. Make sure to put the correct rings in the correct
positions, this can be determined by looking at
the instructions given with the new rings. Each ring manufacturer is different so be sure to check for your
specific rings. Once the rings have been installed you can now fit the connecting rod bearings into the end caps
and lube them up with oil or lithium grease. The piston can now be lowered into the cylinder, make sure the dot
or mark is facing the front of the engine and that you don't scratch the cylinder.
Once installed you can match the connecting rod caps with the correct rods and start to torque the connecting
rod bolts to 10 ft-lbs and then to 40 ft-lbs followed by an additional 90 degree turn. After all are done rotate the crank
to ensure all pistons move smoothly in and out of their cylinders and nothing binds.
When installing the oil pump be sure to use the proper sealant around the pump base if neccessary to ensure that oil pressure
doesn't drop due to leakage. Both surfaces should be cleaned and preped prior to installing. After preparing the contact surfaces carefully
install the oil pump onto the engine and torque down the pump mounting bolts to 20 ft-lbs. Be sure to tighten down the bolts in a cross pattern
to ensure that even torque is applied to the pump. From here we can install the oil pump cover and torque down its bolts to 8 ft-lbs. The oil pump
pickup tube can be installed and torqued down to 20 ft-lbs.
The first thing you must do when installing cylinder heads is to ensure both the block and head surfaces are
completely clean from dust, oil, and any debris. The next thing you must to is
to set the camshafts to their correct positions to prevent any valves from hitting pistons during installation
and torquing of the head bolts. Much the same you have to set the pistons to their correct
locations, typically this means putting the #1 piston to TDC or Top Dead Center. Once everything is ready you
can install the head gasket onto the engine block by aligning the alignment dowels.
Something I usually do is spray down the head gasket with some engine copper spray from permatex which you can
find here, this ensures that any gaps that could be present between the 2 surfaces gets filled with the
spray. It
also helps to transfer heat between the 2 metals. With the gasket in place you can set the cylinder head onto
the gasket and block, if needed have someone assist with this process as the head can be heavy
and you don't want to scratch anything or drop it! Once the head has been placed you will want to start
installing the head bolts to make sure it doesn't move. Be sure to buy new head bolts as many manufacturers
use TTY or Torque to Yield head bolts meaning they stretch during torqueing and cannot be used twice. Also make
sure to lubricate the bolts in clean engine oil before installing them into the head.
Once all the head bolts have been installed and finger tightened you can start the torqueing process, almost all
head bolts have a multi-step process for torqueing. The 4.0L SOHC engine uses two different sizes of cylinder head bolts with a total of
11 bolts being installed into the cylinder head. The 8 main bolts located on the sides of the cylinder heads should be torqued down to
35 ft-lbs and then 55 ft-lbs followed by an additional 90 degree turn. The 3 small head bolts per each cylinder head can be torqued down to
20 ft-lbs. Make sure to not overturn or underturn any bolt as this can cause an unbalance of surface pressure between the gasket and head.
Dodge Nitro 4.0L Cylinder Head Main Bolt Torque Specs : 35 ft-lbs + 55 ft-lbs + 90°
Dodge Nitro 4.0L Cylinder Head Small Bolts Torque Specs : 20 ft-lbs
Timing Belt and Camshaft Installation
On the Dodge 4.0 SOHC engine the timing system is ran by the use of a single timing belt. This belt system consists of a sprocket on each camshaft located at the top
of each cylinder head followed by a water pump sprocket located in the center of the engine, a tensioner sprocket, and a crankshaft sprocket.
When installing new timing belt be sure that the engine is turned so that
the number 1 cylinder is set to TDC or top dead center. From here simply slide the camshafts into the cylinder heads and install the retaining bolts by tightening
them down to 20 ft-lbs. With the camshafts installed you can move to installing the cylinder head rocker shafts. The rocker shafts can be torqued down to 22 ft-lbs.
From here we can hold the camshafts with a large wrench or tool and install the camshaft timing sprockets and torque them down to
85 ft-lbs plus an additional 90 degree turn per bolt. The crankshaft timing sprocket can then be installed onto the crankshaft by aligning the woodruff key with the slot on the sprocket.
From here the belt can be set in place by running from the crankshaft to each camshaft sprocket and then looping
down to the water pump sprocket as shown in the picture. Be sure to align the timing chain marks with the dots on each sprocket to ensure that the timing is set correctly.
Next we can install the timing belt tensioner sprocket which will hold the belt tight during operation. The timing belt tensioner bolt can be torqued down to
20 ft-lbs. With that installed the timing belt should be tightened. Be sure to double check the timing marks before moving onto the next section.
Dodge Nitro 4.0L Water Pump to Block Torque Spec : 8 ft-lbs
Dodge Nitro 4.0L Crankshaft Position Sensor Torque Spec: 8 ft-lbs
Timing Cover Installation
The timing cover on the 4.0L is used to cover up the internals of the engine and hold in massive amounts of oil. For this reason I recommend using
some silicon sealant along with a new gasket during installation. Be sure to clean all of the metal surfaces prior to installation and placing the silicon onto the metal.
With everything ready to install be sure to double check your timing and engine internals before placing the cover in place. Another tip is to lube up the
crankshaft seal with some oil so it seats better. If everything is good to go then place the cover
onto the engine block and begin to tighten down the bolts hand tight. Once all of the bolts have been set in place be sure to follow your sealants instructions by waiting the recommended
time. Once ready you can torque down the larger timing cover bolts to 40 ft-lbs and the smaller bolts to 8 ft-lbs by going in a cross pattern.
Much like the timing cover on the 4.0L the oil pan plays an important role in keeping the engine oil inside the
engine. For this reason I recommend using a new gasket as well as some silicone sealant
during installation. Using the same technique as before with the cover you clean the surfaces of both the oil
pan and the engine block and then install the new gasket onto the block and then follow
it up with some silicone sealant. Be sure to follow your sealants instructions to ensure you get the best seal
from your application. The oil pan larger bolts can be torqued down to 18 ft-lbs and the smaller bolts can be torqued down to 8 ft-lbs by following a cross pattern.
Along with the pan is the oil pan drain plug, this gets removed and reinstalled quite frequently and can be
torqued down to 20 ft-lbs.
Dodge Nitro 4.0L Oil Pan Torque Specs (M6): 8 ft-lbs
Dodge Nitro 4.0L Oil Pan Torque Specs (M8): 18 ft-lbs
The valve cover installation is rather simple, there are rubber seals for each bolt hole and a silicone gasket
that prevents oil from leaking out of the engine. It is recommended to replace both the seals
and the gaskets although if they are in good condition you can reuse them. If you do choose to reuse them I
would use some silicone sealant along with the silicon gasket to ensure it does not leak.
The valve cover bolts torque down to 106 in-lbs or about 8 ft-lbs in a criss cross order. Be sure not to miss
any bolts to avoid having oil leak out onto the exhaust pipes and cause a lot of smoking.
When installing the intake manifold you want to make sure you have all the surfaces as well as intake holes
cleaned out before placing the manifold into position. Once cleaned you can then place
the intake manifold gaskets onto the alignment pins. If you want you can also use a little bit of sealant on the
gaskets to help ensure there are no leaks. With the gaskets in place you can now put
the manifold down onto the gaskets and begin to install the bolts. The intake manifold larger bolts torque down to 20 ft-lbs while the
smaller bolts can be torqued down to 8 ft-lbs in a cross pattern.
The ignition coil assembly can be torque down to 8 ft-lbs and the spark plugs themselves can be
torqued down to 13 ft-lbs, be careful not to overtorque these as they can snap and cause big problems.
When installing the throttle body make sure that all of the gaskets are in good condition and will hold a seal as you do not
want to be leaking gas fumes around the engine. If everything looks good you can tighten the throttle body bolts down to 8 ft-lbs.
Dodge Nitro 4.0L Throttle Body Torque Specs : 8 ft-lbs
Exhaust Manifold Installation
The exhaust manifold can be installed by cleaning the surface areas on both the head an the manifold itself and
then by using the exhaust manifold gasket and putting it in place. Once the gasket is in its
location you can put the manifold onto the heads and begin to torque them down to 18 ft-lbs. I always use some
copper spray from permatex on the exhaust manifold gaskets to ensure I do not end up with
any exhaust leaks once done. When you go to install the engine into the vehicle or if it is already in the
vehicle the torque specs for the exhaust manifold to the exhaust pipes or catalytic converter is 30 ft-lbs.
The water pump on the Dodge 4.0L engine gets tightened down to the engine block on the inside and is ran off of the timing chain.
When removing the old water pump be sure that you drain out the coolant prior to removal otherwise the coolant will spill all over.
Once drained you can remove the water pump mounting bolts and remove the old pump from the vehicle. From here we can clean up the engine blocks
mating surface and prepare the new water pump for installation. Be sure to use a new gasket and some silicon sealant to ensure that no coolant
ends up leaking and causes further engine damage down the road. Once prepared you can install the pump onto the engine and hand tighten the bolts down.
Once all of the bolts have been installed you can then torque down the bolts to 8 ft-lbs. Make sure to follow your sealants instructions as they often
require you to wait an extended amount of time before torqueing down the bolts. Be sure to check out the timing chain section for more information regarding
installing it.
Dodge Nitro 4.0L Water Pump to Case Torque Specs : 8 ft-lbs
Front Dress and Pulley belt Installation
Most of what is left on the engine is just place and tighten objects such as the belt pulleys, belt tensioner,
throttle body, oil filter neck, crankshaft pulley, and motor mounts. If the items have a gasket and hold either
oil or coolant inside the engine then feel free to add some sealant along with the gasket. Always be sure to
inspect your gaskets and replace them if there is any deteriation or flaws with them. For the
belt system the crankshaft pulley gets tightened down to the crankshaft at 70 ft-lbs.
The drive belt tensioner can be tightened to 33 ft-lbs and the idler pulley can be torqued down to 16 ft-lbs. When installing be sure they
both turn smoothly and if they do not then replace them with new ones as the bearings can go bad. The engine
motor mount can be installed onto the engine block if it hasn't been already, the torques for
the mount to the block is 45 ft-lbs and then when installing the mount to the vehicle or frame it can be torqued to
45 ft-lbs. Finally the throttle body can be installed on top of the intake manifold
with a good gasket and some added sealant using 7 ft-lbs in a criss cross pattern. For installing the belt you
can use a tool to move the tensioner into its springed state and install the belt as shown in the
picture. The generator or alternator can be tightened down to the engine block using 30 ft-lbs of force.
The power steering pump can be installed and torqued down to 18 ft-lbs and finally the A/C compressor can be torqued down to
15 ft-lbs of force.
