Harmonic balancer/damper - How to remove and install

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by: Cobalt327, Jon, Mikerrr
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Contents

Overview

The harmonic balancer or damper is usually a tight press-fit onto the end, or "snout" of the crankshaft. This is so the torsional vibrations of the crankshaft generated by the power pulses of the engine can be transmitted to- and absorbed or dissipated by- the harmonic balancer. If the fit isn't tight, the harmonic balancer will not be able to absorb the vibrations and in some cases this can lead to a failure of the crank or damper key/keyway that locates the damper on the crankshaft in the correct position, or the retaining bolt could fail, not to mention possible internal engine damage resulting from the undamped harmonics.

Tools

It is always advisable to use a dedicated removal tool for damper removal. To do otherwise risks damaging the damper beyond repair, damaging the crankshaft or other related parts and covers, or causing personal injury. Because of how tightly most dampers are pressed onto the crank, there's basically no way a damper should be able to be pried off anyway (one possible exception is the Pontiac V8, its damper is sometimes a tight hand fit, having a torque of 120 ft/lb for the 1/2-20 retaining bolt. Heat cannot be used because there could be damage to the damper oil seal. Also most dampers have an elastomeric band that separated the inner hub from the outer inertia ring. Heat can ruin the bond between the two, causing catastrophic failure of the damper that could damage the radiator, water pump, front mounted accessories, the hood, could possibly sever engine oil or ATF cooler lines, radiator hoses, etc.

While there are cheap pullers available that are usually good for a couple uses before it strips out or bends, unless this is a one-time repair and it's not anticipated to ever be done a second time it's always a good idea to invest in a quality tool that's made to last.

Summit p/n G1025 damper puller/installer tool
Cheap puller
Damper installer tool, metric and inch crank threads


Crank bolt removal

Many engines use a bolt to hold the damper on. In some cases like the Pontiac V8, the bolt torque is significant- 160 ft/lb. This means removing it with the engine in the vehicle can be difficult. On some engines just the engine compression and the friction from the belt-driven accessories will allow the bolt to be removed.

An impact wrench will almost always remove the crank bolt without needing to hold the engine from turning. But the room between the bolt and radiator seldom allows an impact wrench to be used. If you have a helper, they can use a lever to hold the flex/flywheel from turning. You can also run a pry bar or other similar prying tool through the puller bolts and wedge this tool against the vehicle frame, firewall, or ground to keep the crank from turning.

An old trick for locking up the engine is to remove the plug from an easy-to-reach cylinder and bring it up to TDC on the compression stroke. Then turn the crank CW some more (past TDC), and using clothes line cord or similar, fill the cylinder up w/the cord. Rotate the engine CCW until it stops turning, then you can loosen the bolt. Reversing this procedure allows the bolt to be torqued- just be sure to remove/replace the cord after repositioning the crank/piston position so you're not bearing down on open valves.

Damper/balancer removal

The pulley and anything else in the way is first removed so the damper can be accessed.

The puller is installed using the same thread bolts that secured the bottom pulley. The procedure shown is for most engines up until the LS-series Chevy and the Gen 3 Hemi, etc.

Start out with the puller center screw lubricated well. Most cranks will have a recess for the puller shaft nose to index on.

Balancer puller installed.jpg

On the Chevy V8 the bottom pulley bolt thread size is 3/8-24. Most engines will be either 5/16-18 or 5/16-24 or 3/8-16 or 3/8-24. You won't be able to use the original pulley bolts; most puller sets come with an assortment of bolts, otherwise find three that are the same length and long enough to use the puller.

Take the bolts down evenly so the puller is centered on the snout then use a breaker bar to tighten the puller. The crank may try to turn once the puller is tight; you can run a prybar through the puller bolts to hold the engine from turning, or get a helper under the vehicle to hold the flexplate or flywheel. If it's a manual trans you can put it in gear and set the parking brake and block the wheels to keep the engine from turning over.

Don't be tempted to use an impact wrench on the puller. This will damage the threads if over done. Keep turning the center screw of the puller until you feel/see the damper start to back off the crank. Once it starts, most of the time it will come off the rest of the way easily. Don't let the damper drop onto the floor.

Once the damper is off, remove the puller bolts and store the tool away for the next time. If the damper is to be reused, clean it off first, coat the snout inside and out with motor oil and store away from rain, etc.

Installation

With threaded damper bolt hole in crank

If the crank snout is threaded, the use of a harmonic damper installer is possible. Simply follow the directions that come with the tool to install the damper, or see the instructionshere. Use RTV in the crankshaft and damper keyway to keep oil from migrating through the key slot to the outside. Also be sure to grease the tool threads and the thrust washer to prevent galling.

Torque the pulley and crankshaft bolts to spec.
Warning Note: Fastener torque has torque values for various engines. If your engine isn't covered, use the appropriate table to find the torque by the size/thread of the bolt.

Without threaded damper bolt hole in crank

Some SBC engines from 1968-back came with the damper installed at the factory with no drilled and tapped hole in the crankshaft snout for a retainer bolt. Removal isn't affected by this, however installation IS.

Drilling the crank snout

The ideal solution is to drill and tap the snout with 7/16-20 threads. This must be done correctly, with the hole drilled and tapped concentric to the crank c/l. If there's any question about this, let a machine shop handle the job.

Hardware

An ARP damper bolt and washer may be used. Torque it to their specs, or to 60 ft/lbs if using an OEM bolt/washer with clean oiled threads. If there is access to good quality grade 8 hardware, a 7/16-20 x 2.25" long bolt with a 1/4" thick washer can be used.

Proceed without drilling the snout

If drilling/tapping the snout isn't possible, the hobbyist engine builder can install the damper using a block of wood and a heavy hammer or short sledge. This operation requires eye protection

There are a couple things that will help ease the job.

  • The damper is held on by a 0.0007"-0.0014" press fit. Heating the damper in 200ยบ F hot water for 15 minutes will cause it to expand a bit. Overheating the damper risks damaging the damper and/or the front seal. Chilling the crank snout with a bag of ice will shrink the crank a bit and is a much more effective and safer method of easing installation without a threaded crank.
  • Use a sturdy block of wood like a 4-5" thick slice of a wooden fence post or 4x4- used grain-on, not across grain to help keep it from splitting- you'll be hitting it fairly hard in most cases, especially if no heat/cold is used. The wood is used to insulate the damper inner hub from the hammer blows.
Warning Warning: NEVER hit the damper on the outer ring- this can break the bond between the rubber and steel, making the damper useless. NEVER hit the damper metal to metal with a hammer. A damaged damper could fail, possibly causing personal injury and damage to the vehicle or even bystanders. Use gloves and eye protection at a minimum.

Below is how the factory recommended installing a SBC 265 cid engine damper without a threaded crank snout:

Sbc damper install non threaded crank.jpg

NOTE: The reference to threading capscrews to hold the hub and "flywheel" in place is for a 265 cid SBC that used a pulley and hub riveted to the flywheel. These were not actually dampers per se; they contained no rubber or other means of absorbing/dissipating harmonics.

Harmonic damper install- honing to fit

(NOTE: This was previously a separate article originated by Techinspector1, Harmonic damper install. The two articles were combined into this article.)

The question arose the other day when someone suggested honing a damper hub in order to get it to press onto the crank snout of a SBC a little easier. Another contributor said there was no way he would hone a damper. The following is my reply:

Normally, I wouldn't hone one either, knowing that the intended purpose of the damper is to transfer harmonics from the crankshaft to the inertia ring on the damper and also knowing that if the fit on the crank snout is too loose, that these harmonics will not be transferred and could result in a cracked crankshaft.

I think what the contributor is saying is that most of these aftermarket offshore dampers are bored about one and a half thousandths (0.0015") too tight, making the press fit dimension about 0.003" interference when it should actually be about 0.0010" (one thousandth) to 0.0015" (one and a half thousandths) interference. Visually inspect the crank snout closely for burrs or nicks that might interfere with the smooth installation of the damper. Use a fine file and/or emery cloth to smooth the surface. Check how far the key sits proud of the crank surface and measure the depth of the keyway in the damper. You want to make sure the key is short enough off the crank surface to not interfere with the roof of the keyway in the damper to prevent the damper from being installed at all.

Measure the snout of the crank about halfway back (the crank snout is tapered) with a known accurate micrometer that reads to the fourth place (ten thousandths of an inch). The snout should measure within one thousandth from low to high tolerance of the specified diameter from the factory (1.2460" / 1.2470"). Let's say for grins that it measured 1.2467". Take that measurement and the damper to your local machine shop and tell them to hone the damper hub to 1.2452" /1.2457". The 1.2452" hole would give you a 0.0015" interference fit. The 1.2457" hole would give you a 0.0010" interference fit. Either one will work and will give the machine shop a half thousandth to play with. If they can't hold a half thousandth tolerance, you have chosen the wrong shop to do the work. Don't try to do this with a brake hone at home. You'll just egg shape the hub and FUBAR the whole mess.

Now, on your way home from having the machine shop hone the hub of your damper, stop by and pick up some dry ice. Once you get home, break up the dry ice into a one gallon baggie and wrap it loosely around the crank snout. Put the damper in a pan of water and bring it to a boil on the kitchen stove. Remove the pot from the stove and carry the whole thing to the garage. Remove the dry ice baggie from the crank snout. Spray the crank snout with WD40. With gloves on to prevent burning your hands, place the damper onto the end of the crank and engage your install tool.

Measuring points of damper and crank snout
Crank snout OD; damper ID; key/keyway dimensions

(NOTE: Two drawings immediately above from Professional Products)

References

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