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Installing a new timing chain and sprockets during engine rebuild.

Fix A Connecting Rod Knock - GM 4.3 V6:

Engine Rebuild Part 8 -
Timing Chain, Harmonic Balancer, Etc.

May Also Apply To Chevy / GMC
350 Cubic Inch V8 Engines

In This Article:
A new timing chain and sprockets are installed. The timing chain cover is replaced and the harmonic balancer is installed with a special tool.
Related Articles:
Skill Level:
4 (Advanced)
Time Taken:
About 2 Hours
Bruce W. Maki, Editor
Project Date:
August 2011
By Bruce W. Maki, Editor
By Staff
Start >>


Installing The Timing Chain and Sprockets:

Once the crankshaft and pistons were installed, I installed the timing chain and sprockets. I bought a new set of sprockets and chain for about $60. But first I had to remove the Woodruff key from the old crankshaft and tap it into the slot in the new crank.


Installing crankshaft timing gear.

I slipped the crankshaft timing sprocket over the end of the crankshaft and aligned the slot with the key.



To drive the sprocket all the way onto the shaft, I had to pound it with a hammer and a large socket.

I used this 1-7/16 inch socket from a set of 3/4 inch drive sockets. It's important to hammer uniformly on the sprocket as close to the center as possible, without hitting the key.

Pressing crank timing sprocket into place with large socket and hammer.


Aligning marks on crank and camshaft timing  sprockets.

I turned the crankshaft until the alignment mark on the small sprocket was pointing straight down. (I colored the alignment marks yellow so they would show up in photos.)

I placed the large sprocket on the end of the camshaft and turned it until the mark aligned with the mark on the crankshaft sprocket.



I drizzled some assembly lube all over the timing chain and slipped the chain over the camshaft sprocket first.

Then I placed the chain over the crank sprocket so the gears were aligned properly, and I installed the 3 bolts that hold the cam sprocket to the camshaft.

I tightened the bolts to 20 foot-pounds.

Fastening camshaft timing sprocket after timing chain installation.


Crankshaft position sensor reluctor installed on end of crank.

I installed the crankshaft sensor reluctor on the end of the crank.

I used a 1-1/2 inch socket (from my set of 3/4" drive sockets) to drive this part onto the shaft. The timing gear and reluctor will be held tightly in place by the harmonic balancer.



Installing The Timing Chain Cover:


I removed the crankshaft position sensor from the old timing cover by removing the bolt with an 8mm socket and pushing out the sensor from the inside.

I cleaned up the sensor with paint thinner. The "lower end" gasket set that I bought came with several O-rings, so I replaced the original O-ring when I installed the sensor on the new timing cover.

Removing crankshaft position sensor from old timing chain cover, GM 4.3 V6 engine.


New timing chain cover installed on front of Chevy / GMC 4.3 V6 engine.

I placed the timing cover on the engine and tightened the bolts part way, using a 10mm socket.

I left the bolts loose so the harmonic balancer will establish the exact position of the cover.



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Installing The Harmonic Balancer:


I threaded the adapter into the end of the crankshaft and snugged it with a 12 mm wrench, following the instructions of the balancer remover/installer kit.

Inserting snout adapter into end of crankshaft, for harmonic balancer installer tool.


Placing harmonic balancer on end of crankshaft, GM 4.3 V6 engine.

I slathered some oil on the inside surface of the harmonic balancer and placed it on the end of the crankshaft, making sure to align the keyway with the key in the crank.

I also oiled the surface that rubs against the front oil seal.



I threaded the installer shaft onto the adapter, with the black metal plate so its flat surface was away from the engine.

Note that the 3 bolts used to remove the harmonic balancer are NOT needed when installing the balancer. The black disc just pushes on the harmonic balancer.

Harmonic balancer installer set up to press balancer onto crankshaft.


Using wrenches to turn harmonic balancer installer tool.

I used a 1-1/16 inch wrench to turn the lsrge shaft (which pushes the round plate forward) while using a 5/8 inch wrench to hold the center shaft.

It took a lot of effort to turn the large wrench... I began to wonder if I was destroying some screw threads somewhere. I tapped on the back of the black plate with a big hammer to coax the balancer onto the shaft.

While turning the big wrench, the crankshaft wanted to rotate, so I placed a prybar between the engine block and one of the counterweights built into the crank. Eventually the balancer "bottomed out" and I couldn't turn the big wrench anymore.


Note that the screw threads on the installer/remover tool need to be oiled every time the tool is used.


I removed the threaded adapter that came with the balancer remover/installer set.

Removing threaded adapter from end of crankshaft after installing harmonic balancer.


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An Extra Problem:

Replacing The Engine Mounts:


The driver's side engine mount broke when we removed the engine, so I decided to replace both motor mounts.

These cost about $20 each.

Broken engine mount on GM 4.3 V6.


Example of good engine mount from GM 4.3 V6.

This is what the engine mount is supposed to look like.

There is a long bolt that goes through the holes. The ears sit on a block of metal on the frame which has a hole through it.

The part with the ears is bonded by a piece of rubber to the part with the two J-shaped "prongs", which is bolted to the engine.



Replacing the engine mount is easy when the engine is out of the car.

I just removed the three bolts and installed the new mount. I used some blue (medium strength) thread locker (Loctite) on the threads of the bolts.

New motor mount installed on GM 4.3 liter V6 engine.



Next Page: Part 9 - Installing The Cylinder Heads

Previous Page: Part 7 - Piston Installation

More Info:
Tools Used:
  • 3/4" Drive Sockets: 1-7/16", 1-1/2"
  • Hammer
  • Harmonic Balancer Installer
  • Wrenches: 5/8", 1-1/16", 12mm
  • Misc. Sockets
Materials Used:
  • Timing Chain and Sprockets
  • Timing Chain Cover
  • Motor Oil
  • Engine Mounts (Optional)
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