View Full Version : crankshaft pulley - balancer

07-08-2002, 10:21 AM
I have a '90 SC that was having no troubles at all until about a month ago, it through the crankshaft pulley clean off. It sheared all 4 bolts off and tossed the pulley out of the car!
No one could decide why it would have done this, so i got a new pulley (the original got pretty torn up) and had it replaced. Of course, they had to drill out all 4 studs, but it was still pretty reasonable. Well, Thursday, it did it again! Now there is obviously something going on here. The current theory is that the harmonic balancer is of somehow and causing vibration to pass through to the pulley.
Does this seem like a reasonable theory? If so, how does this just suddenly happen?
What about just putting the pulley back on with Grade * bolts this time?

Thanks all!

07-08-2002, 01:01 PM
The pulley and balancer are balanced as a unit. they can't just be replaced individually. A new assembly is about $225 from Ford and you will need a new bolt and washer also.
Your balancer is bad if you have had two pullies ripped of of it.

As far as the bolts, I think they should be grade 8 bolts. Anyone know?

Was the pulley shaking while running? If it was that stress could break the bolts.

I think you may have another problem. Some load is causing the bolts to shear off. Check out the AC and power steering, they have a lot of belt contact and might be able to break the pulley bolts if they sieze momentarily.


07-08-2002, 01:04 PM
Vibration is what probably caused the second failure! The pulley and the harmonic balancer MUST be balanced as a set.

Surf the main SCCOA pages for information on a good replacement. There is a batch of SC balancers/pulleys which were specially made and are zero balanced, and much more durable.

07-08-2002, 01:49 PM
#1 - As mentioned, the harmonic balancer and the pulley are balanced as a set. If you took the pulley off and didn't mark the orientation of the assembly, you must either have them rebalanced or replaced.

#2 - The Harmonic Balancers on our cars are not good. If they are removed once, they are basically junk. Reinstalling them leads to failure.

#3 - The bolt holding the harmonic balancer on is weak. It should be replaced anytime it is removed. If it's never been removed it would be a good idea to replace it out of hand. They have been known to crack. Ford no longer carries the bolt. The same one for a Mustang 3.8 fits and is a stronger bolt.

07-08-2002, 02:18 PM
Thanks for the replies folks!

Now that I already have a good pulley, am I going to have to get another one with the balancer to keep the unit together? Also I take it from the above replies that I shouldn't be looking at a used balancer either?
Perhaps a use balancer/pulley combo would still be ok?

Can you tell I'm trying to get by on the cheap here?


Kurt K
07-08-2002, 02:37 PM
Unfortunately, your cheap fix will most likely cost more in the long run. I wouldn't take a chance on a used balancer/pulley. As crappy as the factory set is, it's still better than a used set. The BHJ zero balance balancer would be better, but you still need to have it balanced if you reuse the factory pulley. Or you could upgrade to underdrive pulley, but that doesn't sound like an option ($$$).

07-08-2002, 02:50 PM
Another question for you all-
If the pulley and balancer almost must be treated as a unit, why in the world are just pulleys available for sale - even on this site?
Nowhere in the desciption of the underdrive pulley set, does it say one thing about the balancer. If I spent $180 for this pulley set and then had the crank pulley ripped off due to something that lots of folks out there sound like they are not surprised by, I would be rather unhappy!

Looks like I need to get a hold of Ford and order a pulley/balancer set.
When I first had to replace the pulley, they wanted to sell me the set, but they didn't warn me about the dangers, they just said "
Thats just the way they come"

Live and learn!

07-08-2002, 03:07 PM
While it is true that the pulley and the damper are balanced as a unit. The damper itself is neutrally balanced before the pulley is added. It is much easier to balance the damper than the stamped steel pulley part. The pulley is then gross balanced using welded on weights. Then the two pieces are balanced as a unit. If the two together are unbalanced, pins are added to holes that are drilled in the damper to achieve final balance.

The aftermarket underdrive crank pulleys are generally considered to be neutrally balanced since they are machined from a single piece of aluminum stock. To use an aftermarket pulley, you should really pull out any pins that are in the back of the stock balancer.

One other point. The stock pulley and the damper do not have to be marked to go back together. The holes are offset in such a way that they can only be put back together in their proper orientation.

07-08-2002, 03:58 PM
If you have an aftermarket pulley it is neutral balanced.

You will need to remove any balancing pins from the balancer, which is neutral balanced with out the pins


07-08-2002, 05:00 PM
Don't feel too bad about the new pulley with old balancer.

The neutral balance determination is fairly new around here. I think gldiii was one of the first to nail down the specifics on this.

The stock pully is neutrally balanced. When the pulley is added, weights are welded to the pulley or pins are added to the balancer to bring the assembly into balance.

If you buy any aftermarket pulley's or balancers, they will be neutrally balanced.

Thus a aftermarket pulley on a stock balancer requires the balancer to have the balance pins removed to restore neutral balance.

I don't think the instructions with all the aftermarket parts are very specific about that requirement.

07-08-2002, 05:18 PM
I want to thank everyone for their help on this.
Got to be on eof the most useful and responsive forums I have ever used!
Since I have had to drill out studs once already, and done some damage to the balancer the 2nd time the pulley ripped off, I just ordered a new balancer/pulley combo from Ford. Only $192 wiht my Super Coupe club of Iowa discount.

I wish I hadn't wated the time and money replacing the pulley alone the first time, but I didn't stop here first!

Thanks again all!

Craig Bean