Here you can find information regarding the assembly of the Chevy 2.4L DOHC 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 2.4L 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. The first being 10 ft-lbs starting from the middle and going outwards.
The second time around you can go to 15 ft-lbs and then for the third time you turn each bolt an additional 70 degree turn. 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.
Chevy Cobalt 2.4L DOHC Main Cap Torque Specs : 15 ft-lbs + 70°
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 18 ft-lbs followed by an additional 100 degree turn for each bolt. 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 timing cover and apply an ample amount of lubrication to the pumps gear and drive system. You want
to ensure that when the engine first starts that there is plenty of lubrication already at the pump. Once lubed up you can install
the oil pump cover to the timing cover and torque down the cover bolts to 8 ft-lbs. From here make sure that the pumps drive turns smoothly
so that when it is installed onto the crankshaft there will not be any issues with alignment. I always put a little bit of oil on the crankshaft
seal to ensure that when you install the timing cover it seats properly.
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. On Chevy DOHC engines there is occasionally
bolt holes on the engine block that cross into water passages. Any hole that does this should be installed with some silicon sealant.
A little goes a long way in this step and you can check holes by shining a flashlight down them and looking in the water jackets.
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 2.4L DOHC engine uses 2 different sized head bolts being longer ones and
short ones. The shorter bolts go on the outer side of the cylinder head and get tightened down to 26 ft-lbs. The long
bolts go in the center of the cylinder head where the oil can access. If you are not sure where each bolt goes when you drop
them into the holes they should all start out at around the same height. If one bolt is higher up than the others it is in the wrong hole. The longer
bolts get tightened down to 22 ft-lbs and then a 155 degree turn.
Be sure to tighten the right bolts to the right specs as this is a critical component of the engines functionality.
On the Chevy 2.4 DOHC engine the balancer shaft timing system is directly behind the engines timing chain and also runs the water pump.
This timing chain system is rather large as shown in the picture and uses multiple timing chain guides. When removing the old chain and components
simply just loosen up the chain guides and the balancer shaft sprockets and retaining bolts in order to pull them out. When installing new parts
be sure to install all sprockets before installing the guides and torqueing them down. The balancer shaft retaining bolts can be torqued down to
8 ft-lbs. The balancer timing guides can all be torqued down to 8 ft-lbs along with the chain tensioner. The water pump itself is covered in another area
of this webpage further below. Once everything has been installed and torqued properly be sure to move to the camshaft timing procedures.
On the Chevy 2.4 DOHC engine the timing system is ran by the use of a chain. This chain system consists of a sprocket on each camshaft along
with an externally installed tensioner, guides and a crankshaft sprocket. To remove the old timing chain system simply remove the side tensioner
and remove the chain from the system along with the guides and corresponding sprockets. When installing a new timing chain start with
ensuring that the balancer shaft timing system is installed and timed correctly. That portion is covered just below this section. Once confirmed
you can start by installing the camshaft and crankshaft sprockets and torqueing them down. Starting with the crankshaft sprocket you can slide it onto
the crankshaft while aligning the woodruff key with the slot on the sprocket itself. Make sure that the timing dot is facing towards the 5 o'clock
direction so that the No1 piston is at TDC or top dead center. Next we can begin to install the intake camshaft and its sprocket. When placing the
intake camshaft into its position ensure that the INT diamond is facing towards the 2 o'clock position and the EXH diamond is facing towards the
exhaust camshafts location. The timing chain should have yellow or black painted marks which will align directly to the dots on each sprocket.
Be sure to have the chain around the sprocket as you drop it into place as this is the easiest way to get the chain into position.
Once ready you can install the camshaft bearing caps and torque them down to 8 ft-lbs, be sure that the lifters and rockers
are all in place as you torque the camshaft down this torque is the same for the exhaust camshafts bearing caps as well. Now that the camshaft is installed
we can hand tighten down the sprocket bolt. Be sure to use new sprocket bolts for each camshaft as the old ones are TTY bolts and can only be used once.
Next we can slide the timing chain tensioner down from the top of the engine and then torque its bolt down to 8 ft-lbs. From here we can bring the chain up
to the exhaust camshaft and drop in the exhaust camshaft sprocket and wrap the timing chain around it while aligning the mark with the sprocket dot.
Once aligned hand tighten up the exhaust camshafts sprocket bolt to ensure it stays put. The right side timing chain guide can now be installed from the bottom and
torqued down to 8 ft-lbs. Once you have tightened down the bolt through the access hole you can install the plug and torque it down to 66 ft-lbs.
Now the timing chain primary tensioner can be installed into the rear side of the engine and torqued down to 55 ft-lbs. Once in you can activate it by
pressing inwards on the plunger from the top of the engine. It should tighten up the chain and take out slack. You can also turn the engine slightly
clockwise to help the tensioner tighten the chain. Now that the timing chain is in place and tightened down we can torque the camshaft sprockets to
specification. Be sure to hold each camshaft with a 24mm wrench as you torque on the sprocket bolt. The camshaft sprocket bolts can be
torqued down to 62 ft-lbs and then an additional 30 degree turn. Once both have been tightened install the upper guide and torque it to 8 ft-lbs.
From here the timing system has been installed and you can move onto the next step of the engine.
The timing cover on the 2.4L 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 the timing cover bolts can be tightened down to 18 ft-lbs. Be sure to not overtighten these bolts as it can be easy to do so.
Much like the timing cover on the 2.4L 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 bolts torque to 18 ft-lbs in a cross pattern design.
Along with the pan is the oil pan drain plug, this gets removed and reinstalled quite frequently and can be
torqued down to 18 ft-lbs.
Chevy Cobalt 2.4L Oil Pan Torque Specs : 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 bolts torque to 8 ft-lbs
and can be tightened 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.
Chevy Cobalt 2.4L 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 it down to 10 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 20 ft-lbs.
The water pump on the Chevy 2.4L engine should be installed prior to installing the timing chain and balancer timing chain
as the pump itself is ran off of the balancer chain. When removing the old water pump be sure to remove the entire balancer shaft
timing chain or to hold the chain as the pump is removed and replaced. Failure to do so will result in the timing to be off and catastrophic
engine failure. This is why I always recommend removing the chain system to ensure further engine damage does not resolve. The pump itself
has a giant metal pipe that connects to the rear end of it which is used to transport coolant throughout the engine. It seals using an O ring
that I recommend coating with some sealant to ensure that it seals properly and no leaks develop. The pump itself can be torqued down to the
engine block using 18 ft-lbs of force. The water pumps sprocket can be torqued down to 8 ft-lbs and then the balancer timing chain can be installed
and continued. On the other end of the pump the housing bolts can be torqued down to 8 ft-lbs. If you happen to access the pump through the access
plate on the timing cover be sure to tighten up the plate bolts to 8 ft-lbs. Make sure you have a good gasket or some sealant as oil can leak through
the plates sides if a leak occurs.
Chevy Cobalt 2.4L Water Pump to Block Torque Specs : 18 ft-lbs
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 74 ft-lbs and then an additional 125 degree turn.
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 59 ft-lbs and then when installing the mount to the vehicle or frame it can be torqued to
35 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 17 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.
