2002 - 2009 Chevy Trailblazer 4.2L Torque Specs

2008 Chevy Trailblazer 4.2L Complete Torque Specs List

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Chevy Trailblazer 4.2L Repair Information

Chevy Trailblazer 4.2L Engine Repair Information

Here you can find information regarding the assembly of the Chevy 4.2L 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

Chevy 4.2L engine block
The 4.2L 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 18 ft-lbs and then for the third time you do 2 additional 90 degree turns for each bolt for a total of 180 degrees. Once finished you should be good to continue with the rest of the engine.

Chevy Trailblazer 4.2L Main Cap Torque Specs : 18 ft-lbs + 90° + 90°

 

Piston and Connecting Rod Installation

Chevy 4.2L piston ring 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 18 ft-lbs and then an additional 110 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.

Chevy Trailblazer 4.2L Connecting Rod Torque Specs : 18 ft-lbs + 110°

 

Oil Pump Installation

Chevy 4.2L oil pump installation
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. After preparing the contact surfaces carefully install the oil pump onto the crankshaft by aligning the crankshaft end with the hole on the center of the pump gear. Once installed you can then place the bolts into the holes and tighten them down to 8 ft-lbs. The oil pickup tube on this engine then bolts up to the bottom of the oil pump through the use of a single bolt. This bolt can be tightened down to 8 ft-lbs along with the tubes retaining bolt. The oil pump pressure relief valve can be torque down to 10 ft-lbs if it has been removed for any purposes.

Chevy Trailblazer 4.2L Oil Pump Torque Specs : 8 ft-lbs

Chevy Trailblazer 4.2L Oil Pickup Tube Torque Spec : 8 ft-lbs
Chevy Trailblazer 4.2L Oil Pump Pressure Relief Torque Spec : 10 ft-lbs

 

Cylinder Head Installation

Chevy 4.2L cylinder head installation
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 4.2L uses 3 different sizes of cylinder head bolts in its engine. In total there are 10 medium sized bolts, 2 short bolts, and one long skinny bolt. The medium sized bolts start off with 22 ft-lbs and then get turned an additional 155 degree turn going through each bolt one at a time. For the short bolts you can tighten them down to 5 ft-lbs and then a 60 degree turn. The long bolt can be torqued down to 5 ft-lbs as well but then a 120 degree turn. After torquing the heads are completely installed and you can now move to intalling the timing.

Chevy Trailblazer 4.2L Cylinder Head Torque Specs (Medium): 22 ft-lbs + 155°

Chevy Trailblazer 4.2L Cylinder Head Torque Specs (Short): 5 ft-lbs + 60°

Chevy Trailblazer 4.2L Cylinder Head Torque Specs (Long): 5 ft-lbs + 120°

 

Timing Chain and Tensioner Installation

Chevy 4.2L Timing chain installation
On the Chevy 4.2 engine the timing system is ran by the use of a timing chain. This chain system consists of a sprocket on each camshaft, a tensioner, timing guides, and a crankshaft gear. Before the chain can be put into place you need to make sure that all of the gears are in their proper positions. Make sure that the intake and exhaust camshaft sprockets and actuators are torqued down properly. The intake camshaft sprocket gets torqued down to 15 ft-lbs and then a 100 degree turn. The exhaust camshaft actuator gets tightened down to 18 ft-lbs and then a 135 degree turn. The crankshaft sprocket simply slides into place and aligns using a woodruff key that installs into the cranks shaft. Be sure that both camshafts bearing caps have been installed properly and torqued down to 8 ft-lbs. From here we can install the timing chain and align the painted chain links with the dots on each sprocket. Once aligned we can install the timing chain guides and torque them down to 13 ft-lbs. The top timing chain guide gets tightened down to 8 ft-lbs. With all the guides in place you can install the timing chain tensioner and torque it and its shoe bolt down to 18 ft-lbs. From here you can pull the tensioner holder and the chain should tighten up and stay in place. Double check the timing before turning over the engine and ensuring that nothing binds up. If you also need to work on the rear timing chain which runs the balancer shafts off of the crankshaft be sure to check out that section just below.

Chevy Trailblazer Intake Camshaft Sprocket Torque Spec: 15 ft-lbs + 100°

Chevy Trailblazer Exhaust Camshaft Actuator Torque Spec: 18 ft-lbs + 135°

Chevy Trailblazer Crankshaft Position Sensor Torque Spec: 8 ft-lbs

Chevy Trailblazer Camshaft Bearing Caps Torque Spec : 8 ft-lbs

Chevy Trailblazer Timing Chain Guide Torque Spec : 13 ft-lbs

Chevy Trailblazer Timing Chain Top Guide Torque Spec : 8 ft-lbs

Chevy Trailblazer Timing Chain Tensioner Torque Spec : 18 ft-lbs

 

Balancer Shaft and Timing Installation

Chevy 4.2L Balancer Shaft installation
On the Chevy 4.2 engine there is a rear timing chain that runs the engines balancer shafts which mitigate the engines vibrations. The balancer shafts run off of a timing chain that also connects to the rear end of the crankshaft. In order to change this timing chain you will need to remove the transmission from the engine and then remove the rear timing chain cover. From here we can see both of the balancer shaft sprockets along with the crankshaft sprocket which is fixed to the crank itself. To install a new balancer shaft simply remove the timing chain guide and then remove the corresponding balancer shaft sprocket and shaft retaining plate. The shaft will then pull out and can be changed. In order to change the rear timing chain you just need to remove the timing guides and then remove the old chain with a new one and then align the black painted chain marks with the dots on the sprockets. Once aligned simply reinstall the timing guides and torque them down to 8 ft-lbs. The tensioner bolt can also be installed and torqued down to 8 ft-lbs. The balancer shaft retaining bolts can be torqued down to 8 ft-lbs as well. The cover that keeps the oil in the engine and protects the rear timing chain can be installed with a new gasket and some silicon sealant and then torqued down to 8 ft-lbs.

Chevy Trailblazer Rear Timing Chain Guides Torque Spec: 8 ft-lbs

Chevy Trailblazer Rear Timing Chain Tensioner Torque Spec: 8 ft-lbs

Chevy Trailblazer Balancer Shaft Retaining Bolt Torque Spec: 8 ft-lbs

Chevy Trailblazer Rear Oil Housing Bolts Torque Spec : 8 ft-lbs

 

Front Timing Cover Installation

Chevy 4.2L Timing cover installation
The front timing cover on the 4.2L is used to cover up the main timing chain and retain engine oil inside of the engine. For this reason I recommend using a new timing cover gasket and some silicon sealant to ensure that the cover does not end up leaking. Once both contact surfaces have been cleaned and the new gasket and silicon is in place and ready you can place the cover onto the engine and tighten down the cover bolts to about 8 ft-lbs. Be sure to follow your silicon sealants manufacturers instructions as some require you to hand tighten the bolts and then wait an extended period of time before torqueing them down.

Chevy Trailblazer Timing Cover Torque Specs : 8 ft-lbs

 

Oil Pan Installation

Chevy 4.2L Oil Pan installation
Much like the timing cover on the 4.2L 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 uses 2 different sets of bolts being the side bolts and the bolts that go up from the bottom of the pan. The side bolts can be torqued down to 18 ft-lbs and the normal bolts can be torqued down to 8 ft-lbs. Along with the pan is also the oil drain plug which is commonly removed and reinstalled. This can be torqued down to 18 ft-lbs.

Chevy Trailblazer Oil Pan Bolts Torque Specs : 8 ft-lbs

Chevy Trailblazer Oil Pan Side Bolts Torque Specs : 18 ft-lbs

Chevy Trailblazer Oil Drain Plug Torque Specs : 18 ft-lbs

 

Valve Covers Installation

Chevy 4.2L Valve Cover installation
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.

Chevy Trailblazer Valve Cover Torque Specs : 8 ft-lbs

 

Intake Manifold and Fuel Rail Installation

Chevy 4.2L Intake Manifold installation
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 starting from the inside and going outwards. The ignition control module can be torqued 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 fuel rail make sure that all the fuel injectors are in good condition and that all the o-rings are in place and are in good condition. If everything is good you can place the fuel rail into position and push the injectors into their holes and start to torque the rail bolts to 90 in-lbs or about 8 ft-lbs.

Chevy Trailblazer Intake Manifold Torque Specs : 8 ft-lbs

Chevy Trailblazer Ignition Coil Torque Specs : 8 ft-lbs

Chevy Trailblazer Spark Plug Torque Specs : 13 ft-lbs

Chevy Trailblazer Fuel Rail Torque Specs : 8 ft-lbs

 

Exhaust Manifold Installation

Chevy 4.2L 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 the fasteners down to 15 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 35 ft-lbs. The EGR system consists of a series of pipes that range from the manifold to the head. All of the EGR pipes can be tightened down to 14 ft-lbs.

Chevy Trailblazer Exhaust Manifold Torque Spec : 15 ft-lbs

Chevy Trailblazer Exhaust Pipe Torque Specs : 35 ft-lbs

Chevy Trailblazer EGR Pipe Torque Specs : 14 ft-lbs

 

Water Pump and Thermostat Installation

Chevy 4.2L Water Pump installation
The water pump on the Chevy 4.2L engine should be installed by using a new gasket and if desired some silicon sealant to help prevent leaks. Be sure to clean both metal surfaces prior to installing the pump. Also lookup your silicon sealants instructions to ensure that you are doing everything properly. The water pump bolts can be torqued down to 8 ft-lbs, the coolant outlet bolt can be torqued down to 8 ft-lbs and finally the water pump pulley bolts can be torqued down to 18 ft-lbs.

Chevy Trailblazer Water Pump Bolts Torque Specs : 8 ft-lbs

Chevy Trailblazer Water Outlet Bolt Torque Specs : 8 ft-lbs

Chevy Trailblazer Water Pump Pulley Bolts Torque Specs : 18 ft-lbs

 

Front Dress and Pulley belt Installation

Chevy 4.2L Pulley and 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 torqued to 110 ft-lbs plus an additional 180 degree turn. The belt tensioner assembly can be tightened to 37 ft-lbs. The idler pulley bolt can also be torqued down to 37 ft-lbs. When installing be sure it turns smoothly and if it does not then replace it with a new one as the bearing 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 power steering pump bolts should be tightened down to 18 ft-lbs. The A/C compressor can be tightened down to 18 ft-lbs. The alternator mounting bolts get tightened down to 37 ft-lbs.

Chevy Trailblazer Crankshaft Pulley Torque Specs : 110 ft-lbs + 180°

Chevy Trailblazer Belt Tensioner Torque Specs : 37 ft-lbs

Chevy Trailblazer Belt Idler Pulley Torque Specs : 37 ft-lbs

Chevy Trailblazer Motor Mount to Engine Torque Specs : 59 ft-lbs

Chevy Trailblazer Motor Mount to Frame Torque Specs : 35 ft-lbs

Chevy Trailblazer Power Steering Pump Bolt Torque Specs : 18 ft-lbs

Chevy Trailblazer A/C Compressor Bolts Torque Specs : 18 ft-lbs

Chevy Trailblazer Alternator Torque Specs : 37 ft-lbs

 


Front Timing Torque Specs
Front Timing Cover Bolts Torque spec 8 ft-lbs
Front Timing Chain Guide Torque spec 13 ft-lbs
Front Timing Chain Top Guide Torque spec 8 ft-lbs
Front Timing Chain Tensioner Torque spec 18 ft-lbs
Intake Camshaft Sprocket Bolt Torque spec 15 ft-lbs + 100°
Exhaust Camshaft Actuator Bolt Torque spec 18 ft-lbs + 135°
Crankshaft Postition Sensor Torque spec 8 ft-lbs
Camshaft Bearing Cap Bolts Torque spec 8 ft-lbs
Cylinder Head Torque Specs
Cylinder Head Bolts Torque Specs (Medium) 22 ft-lbs + 155°
Cylinder Head Bolts Torque Specs (Short) 5 ft-lbs + 60°
Cylinder Head Bolt Torque Specs (Long) 5 ft-lbs + 120°
Valve Cover Torque specs 8 ft-lbs
Exhaust Manifold Torque specs 15 ft-lbs
Exhaust Manifold to Pipe Torque 25 ft-lbs
Exhaust EGR Pipe Torque Spec 14 ft-lbs
Bottom End Torque's
Main Cap Bolts Torque Spec 18 ft-lbs + 90° + 90°
Connecting Rod Bolts Torque Spec 18 ft-lbs + 110°
Oil Pump Bolts Torque Spec 8 ft-lbs
Oil Pump Pickup Tube Torque Specs 8 ft-lbs
Oil Pan Bolts Torque Specs 8 ft-lbs
Oil Pan Side Bolts Torque Specs 18 ft-lbs
Oil Pan Drain Plug Torques 18 ft-lbs
Intake Manifold and Fuel Rail Torque Spec
Intake Manifold Bolts Torque Specs 8 ft-lbs
Fuel Rail Torque Specs 8 ft-lbs
Ignition Control Module Torque Spec 8 ft-lbs
Spark Plugs Torque Specs 13 ft-lbs
Throttle Body Torque Specs 7 ft-lbs
Rear Balancer Shaft and Timing Torque Specs
Rear Timing Chain Guides Torque Specs 8 ft-lbs
Rear Timing Chain Tensioner Torque Specs 8 ft-lbs
Balancer Shaft Retaining Bolt Torque Spec 8 ft-lbs
Rear Oil Housing Bolts Torque Specs 8 ft-lbs
Water Pump & Pulley Torque Specs
Water Pump Bolts Torque Specs 8 ft-lbs
Water Pump Outlet Torque Specs 8 ft-lbs
Water Pump Pulley Bolts Torque Specs 18 ft-lbs
Crankshaft Pulley Torque Spec 110 ft-lbs + 180°
Belt Tensioner Bolt Torque Spec 37 ft-lbs
Belt Idler Pulley Bolt Torque Spec 37 ft-lbs
Motor Mount (Engine Side) Torque 59 ft-lbs
Motor Mount (Frame Side) Torque 35 ft-lbs
Power Steering Pump Bolts Torque Spec 18 ft-lbs
A/C Compressor to Engine Torque Spec 18 ft-lbs
Alternator to Engine Torque Spec 37 ft-lbs