Harmonic Balancer and Seal

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Originally submitted by T Feb 24th 2006:

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Front view of the Harmonic Balancer for a blue/black engine. Click to Enlargen. Photo by Jacks.

The Harmonic Balancer:

Click to Enlargen. Blue/Black 3.3 Harmonic Balancer. Note that the Red Harmonic Balancer, even though it will fit, must not be interchanged due to the difference in the balanceweights and crankshaft details. Photo by Hairy-Dude


The Harmonic Balancer was invented by Royce of Rolls-Royce fame. Prior to this all 6 cylinder engines broke their crankshafts everytime the revs came up no matter how much metal they had in them nor how heavily they were forged. It seemed these crankshafts were hell bent on destroying themselves with their own momentum and inertia. V6 Harmonic Balancer Link provided by Yogie.
Removing the Harmonic Balancer. Be sure to tap the Centre Bolt occasionally to prevent the Puller causing the Balancer to bind. Click to Enlargen.  Photo by RedWagon.
Harmonic Balancer Balancer Thread Royce began investigating the problem and fitted flywheels to the front of the engine as well as the rear. Though he made no progress he persisted with the idea constantly changing the dimensions of the flywheels in an attempt to solve the crankshaft breaking problem. Eventually, one test resulted in a crankshaft that did not break under high RPM, but to the team's astonishment it had nothing to do with the size of the flywheels. It was found that the Front Flywheel hadn't been tightened down hard enough and was actually flopping back and forward in response to each power stroke.
You can identify this as a Blue/Black Balancer by the fact that there is no Taper on the rear outer edge. The Front Oil Seal surface is in the centre facing up. Click to Enlargen. Photo by Hairy-Dude
Royce investigated things and developed what is now known as an Harmonic Balancer, essentially 2 flywheels seperated by some rubber to allow them to move separately in response to the engine's power strokes.
The remains after a disastrous Balancer Failure. The three small holes are threaded and are for attaching the puller. Photo by Hairy-Dude


Red, Blue and Black Holden 6 cylinder engines have Harmonic Balancers fitted to the front of them that double for ancillary drive. That is, the Fan, Waterpump and Alternator are driven by them. Over time, the Harmonic Balancer can wear out both the rubber cushion inside it and the seal behind it. Note that you should not use a Red Harmonic Balancer on a Blue/Black Engine, nor a Blue/Black Balancer on a Red Engine because there are significant differences in the crankshafts of these Engines.

Removing the Harmonic Balancer:

The only practical way, and the recommended way, to remove the Harmonic Balancer is with the proper puller.

Red/Blue/Black 6 Cylinder Puller:

Red/Blue/Black 6 Cyl Harmonic Balancer Puller Kit. Photo by Jacks.
These are easy to find and so cheap that it makes their purchase appealing.

Grey Motor Puller:

Grey Motor Harmonic Balancer Puller. Click to Enlargen. Image by T.
179 Engine with the Harmonic Balancer removed. Note the locator dowells which some people remove to improve seal alignment. Click to Enlargen. Photo by Jacks.

The Oil Leak:

After a time, the seal behind the Harmonic Balancer can fail and cause an oil leak. The leaking oil drips onto the Harmonic Balancer and gets flung all over the engine eventually having dust stuck to it.
Sometimes the rubber gasket between the Sump and the Timing Cover can go hard, leak and look like a Front Oil Seal leak. Filling the gap with Cylinder Head Bolt Glue will stem the leak provided any Blow-By gases have been arrested first. Photo by Jacks.
The oil leak can deteriorate the rubber that seperates the two halves of the Harmonic Balancer causing the outer part of the Harmonic Balancer to slip. Since the Ignition Timing Mark is mounted there, incorrect Ignition timing can result. The failure of the Harmonic Balancer oil seal is often caused by a score mark that the seal wears into the Harmonic Balancer. If you're ever fitting a used balancer, closely inspect the boss that the seal will run on for any signs of a groove. Replace the Harmonic Balancer if the seal surface is not mirror smooth.
The image shows the surface that the Front Oil Seal runs on. You can identify this as a Red Balancer by the taper on the outer rear edge. Click to Enlargen. Photo by Jacks

Front Oil Seal leaks are not unique to Old Holdens. These leaks are common to many brands of cars including Daimler-Benz, BMW and many japanese cars.

The Unstoppable Front Oil Seal Leak:

Be aware that oil leaks can appear to be from one location when they are actually occuring in another. Look over this link for extra information. Engine Oil Leaks If you suspect the Front Oil Seal has failed, wipe down the whole area and monitor things for a few days. A Dentist's mirror is invaluable for looking into places that don't provide good visibility. An oil leak from the front of a Red/Blue/Black 6 cylinder engine might be caused by the Sump rubber seal having gone hard. It's best to assure yourself that you definitely have a seal leak before you proceed because it's a lot of work. There are occasions where owners find a Front Oil Seal leak that persists despite their best efforts. They replace both the seal and the Balancer yet still the leak persists. Several factors are involved in persistent leaks. Sometimes replacing the Front Oil Seal will not be necessary once the real problems have been cured.

1. Excessive Crankcase Pressure:

This is caused by Piston Rings not holding back the Combustion Charges and is not necessarily due to worn out Bores and Rings. Check out Clearing Piston Ring Grooves for the causes and cure.

2. Excessive Crankshaft Vibration:

If some aspect of the crankshaft has become unbalanced it will stir things up for the Balancer and make it impossible for the seal to maintain a grip on the Balancer.

3. Rough Running:

If the Engine is badly tuned it can cause a combination of Crankshaft Vibration and Blow-By Gases that upset the Seal.

4. Running in a New Front Seal:

Sometimes a new Seal will take a couple of days to wear in a match fit to the Balancer.

5. Worn Crankshaft Bearings:

Excessive end float or bearing clearance can prevent a seal from being maintained.

6. Front Timing Cover Out of Alignment:

There could be various causes of this including a fault in manufacture. Some people solve this by removing the locator dowells from the engine and tightening the Timing Cover after everything has been assembled to allow the Front Oil Seal to find its own level rather than being forced to one side.

7.Insufficient PCV Vacuum:

Either the Engine idle speed is too low or there is a restriction in the PCV hoses preventing vacuum from being applied to the Crankcase.


I have been able to remove Harmonic Balancers without removing the Radiator on Toranas and Kingswoods.

Removing the Harmonic Balancer Seal:

There are lots of ways of doing this. My favourite is to hit the outer edge of the seal with a screw driver and a hammer.
Removing the Harmonic Balancer Seal by tapping it out of shape with a hammer and screwdriver. Photo by Hairy Dude.

Tap the outer edge of the seal so that it gets bent out of shape towards the crankshaft. Take special care not to mark the Crankshaft, the Timing Cover or any metal you don't intend to replace. Once the seal is belted out of shape you will be able to lift it out with your fingers or needle nosed pliers if it still retains resemblance of its former shape.

Replacing the Harmonic Balancer Seal:

This can be done with a hammer. Coat the outer metal edge (the part that will fit against the Timing Cover) with sealant. I use GM(H) cylinder head bolt glue or No.3 permatex .

How to install the seal. Position the Seal in this manner and tap it along the line of the Arrow. Image by T.

Place the seal into the bottom of the Timing Cover and leave the top of the seal butted up against the top. It clearly will not fit in at this stage. Tap the top of the seal with a downward and inward motion at the same time. The intent is that the hammer will cause the outer edge of the seal to compress small enough to fit the housing and simultaneously drive the seal in. Once the seal starts in the housing tap it around in a circle to avoid tapping it in one place. Tapping it in one place only will make the seal bind in that spot and if you keep hitting it there the seal will bend out of shape and lose the spring tension that is designed to hold it in place. The seal will sit proud of the timing case by about 1/8". You will also know that the seal has bottomed when the sound of the hammer taps goes from meaty to thin.

Replacement of the Harmonic Balancer:

On Red, Blue, and Black Holden 6 cylinder engines, the Harmonic Balancer is designed to be hammered on. It is a force fit on the crankshaft. After placing the unit onto the crankshaft hit the centre of the Harmonic Balancer with a heavy hammer. You will most likely need to remove the Radiator to get enough swing on it because it takes about 100 hits to get it on. Make sure you hammer the Harmonic Balancer in the centre area only. Never hit the pully part or you can break the rubber that holds the two parts together. Make your hammer blows around in a circle. Just like installing the Oil Seal, don't hammer in the one place or the Balancer is likely to bind there.

Balancer Comparison:

The red engine balancer has the timing mark in a different position from the blue/black Harmonic Balancer. See the images for detail.  

179 Engine (red). Note that the 0 deg position is to the left of the Timing Case Bolt above it. Click to Enlargen. Image by Jacks.

Identifying Harmonic Balancers:

The position of the Timing Mark is different between the 2 Harmonic Balancers. The Red Balancer has the Timing Mark near the end of the Cutaway Arc. The Blue/Black Balancer has the Timing Mark centred between the Cutaway Arc and the Bolt Hole pointed to by the Crankshaft Keyway.  

The Harmonic Balancer Has Spun on its Centre:

Some posters report that the outer section of the Balancer can rotate on the inner portion making accurate ignition timing impossible. Refer to the Balancer image as a visual check of the timing nick for the relevant Balancer.


Despite being black in colour, the item on the right is a Red Engine Harmonic Balancer. Note the Red Arrow. The Timing Mark is at the clockwise end of the rectangular hole immediately anticlockwise from  the Crankshaft Keyway.   Click to Enlargen. Image by Mark Berner.


Red Engine Harmonic Balancer. Click to Enlargen. Image by HQSS.
Red Engine Harmonic Balancer with marks showing the increased dimensions of  Blue/Black Balancer. Info by HQ_SS and Wombat. Click to Enlargen. Image by HQSS.
Blue/Black Engine Harmonic Balancer. Note the rear side of the V-Belt area is thicker.  Click to Enlargen. Image by HQSS.
Blue/Black Engine Harmonic Balancer. Note the rear side of the V-Belt area is thicker.  Click to Enlargen. Image by HQSS.
Red Engine Harmonic Balancer. The heavy Score Marks mean the whole Balancer and Seal needed replacing. Click to Enlargen. Image by Jolly Roger.


Harmonic Balancer Puller. The Outer Ring of the Balancer is missing. Click to Enlargen. Image by SamWB.


3.3 engine (Blue/Black) Harmonic Balancer. Note the Timing Mark is mid way between the Bolt Hole and the Rectangular Arc marked by the red arrow. Image by Jacks. Click to enlargen.


Worn out and New  Harmonic Balancers. Click to Enlargen. Image by 1963EJ.


Litchfield Tools Harmonic Balancer Puller.  Click to Enlargen. Image by Silver.


3.3 engine (black). Note that the 0 deg position is to the right of the Timing Case Bolt above it. Image by Jesse_Madden.


Litchfield Tools Harmonic Balancer Puller.  Click to Enlargen. Image by Silver.


Harmonic Balancer Bolts:

Three Bolt Holes are in the Harmonic Balancer centre. They are for adding Power Steering and Air conditioning Equipment.  

They are 3/8" UNF. Brett.

Harmonic Balancer Types:

Ben is correct regarding the V8 balancers, they are all the same size. The 6-cyl balancers do change however, & there were several changes. Firstly, Blue & Black 202/3.3 balancers are heavier, the rear ring section is thicker. This is easy to see if you sit the 2 side by side. Blue 173/2.85 balancers are the same (thinner) size as all Red motors. The timing mark position also changed but sadly not exactly at the Red/Blue changeover time. It changed mid-way thru the VC series around the same time as the larger water pump was introduced. The timing tag on the front case had its markings changed from 8º to 12º, while the zero point moved about 8º downwards. This makes early Blue 3.3 balancers very rare because they have the same heavy rear ring as the later ones, but have the timing mark in the Red motor position. Dr Terry

VC-VH-VK (blue/black) Harmonic Balancer. Click to Enlargen. Image by xpanelvanx.


Harmonic Balancer Removal and Replacement  Mark Berner's Shed Failed Harmonic Balancer from 350 ci Small Block Chev 



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