35th Anniversary Thunderbird Registry

Crankshaft Harmonic Damper

There has been an issue develop over time about SC's losing the harmonic damper and pulley while driving. If this happens, the extent of damage that can be done under the hood is almost beyond description. It isn't clear if the center bolt shears off and the damper assembly detaches from the engine or if the vibrational forces over time as the damper gets old puts undue stress on the pulley. It is to your advantage to check the center of the crankshaft damper and pulley assembly to make sure the center bolt is still there. To hopefully bring awareness of this issue, please read the following article and information. Even if you are not mechanically inclined, you will get an idea of the problem that exists with the original unit.

My thanks goes to Duffy Floyd for allowing me to share his knowledge of this subject.

              Harmonic Damper Replacement
 by Duffy Floyd

This is an assembledge of the conventional wisdom on the Harmonic Damper issue we all face.

Fact: People are having problems with damper and/or damper failures. (I have had one myself on the stock 89)

What is not known is exactly why. Steve Webb believes in part that the problem revolves around the method of manufacture of the damper. Ford decided to make the damper hub out of AL as a weight savings (documented in technical information I have) The damper hub assembly is sleeved with steel on the outside. Steve believes this further weakens the assembly since the cross sectional area of the AL is machined down to install the steel sleeve. Steve further believes that multiple installations of the same damper assembly causes problems becuase the AL is "expanded" during the pressing on and pulling off resulting in a looser and looser fitment.

Vernon Cradier confirmed my suspicion that the damper itself is a zero balance unit with no balance pins installed. (I got this inference from the requirement in the shop manual to move balance pins to like configuration if the Pulley is to be reused with a different damper.) If you examine many dampers you will see drill marks where the damper is first balanced after manufacture. Some stamped pulleys also have washers welded on them that. Each item of the assembly is thus balanced as an assembly. The balance pins previously thought to balance the assembly together are not used for that purpose at all. I confirmed this with a Ford Engineer yesterday. The balance pins on the damper and on the flywheel of manual cars (rivets on auto flexplates) were installed at the Essex Engine factory as a final dynamic balance attempt for the ENTIRE Engine.

I believe the damper is a weak link in our engines. V-6 engines are inherently unbalanced in the manner stresses are placed on the crank during the firing order of the cylinders. (confirmed by SAE paper for this Ford 3.8L V-6 basic design). This causes more "work" for the damper to do.

Now what can we do?????????

Vernon has confirmed my suspicion that aftermarket UD Pulley sets are zero balance units. If you install these types of pulleys do not remove the balance pins from the damper.

Consider buying new FORD Units (with the Pulley BTW) if you get in there and remove the damper for some reason. (You may get away with reusing the damper once but after that forget it....get a new unit.)If you must reuse an "old" damper from another source try to get the pulley too. If you can not get the pulley that came with the damper then make sure the balance pins for the replacement damper are in the same spot as the "old" damper that came off your car.

Consider upgrading to an aftermarket all steel damper unit. ....I have one on the 92 and am impressed with this quality piece.

Replace the bolt and loc-tite it if you do a damper replacement. Do not reuse the damper bolt.


Additional information from George Davenport, SCCoA:

The aluminum unit can be damaged if removed incorrectly or as age degrades it's fit onto the crankshaft. Sometimes the crankshaft damper is removed when replacing the crankshaft sensor and old parts are reused. The reasons may vary but the end result is the same.

A new better replacement for the original Ford damper is the one now being produced by BHJ Dynamics.

Super Coupe Performance, at http://www.supercoupeperformance.com/engine.htm,sells these units and explains their application and installation needs. They are available for the early SC (89-93) and late model SC (94-95). A new crank bolt and washer is definitely required as well. Ford no longer carries the SC part, but a 98 3.8L Mustang bolt and washer, as shown above, will work just fine. Part numbers are F58Z-6A340-A (3-pack bolts) and E2DZ-6378-A (5-pack washers).

I highly recommend that should you ever remove the crankshaft damper assembly, either for an engine rebuild or for whatever reason, you consider replacing the damper with this unit. Let the experience of well known SC enthusiasts help you avoid any major problems.

I hope this information is helpful to you. I thank George Davenport for his additional information and photos on this subject.

Additional note: On June 4th, I learned that Ford has reinstated to full status the original SC harmonic damper and pulley assembly. The part number is E9SZ-6B321-C. You can order this assembly at your local Ford dealer or you can try internet sources such as www.fordparts.com . The list price at the dealer was quoted to me as $264.13.
Disclaimer: This article, and additional information, is for personal use only and for assisting owners in maintaining their vehicle. No publishing or reprinting is allowed unless by permission by the author of this article. The author is not responsible for any damage that occurs from the use of this information.