balancer and crank keyway problems

ModusPonens

Registered User
I took the harmonic balancer off my 93 sc to find that the crank keyway chewed into the keyway on the balancer. the crank keyway appears to be only 1/8 to 1/4 inch long, while the keyway on the balancer runs the length of it. It doesn't make sense that such a small key would be responsible for holding the weight of the balancer and all stress behind it. First off- does my problem lie with this crank key not running the full length?

obviously i need a new balancer. the key rotated on the balancer about 10 degrees. Any suggestions on how i can prevent this from happening again?

thanks
Janine.
 
ModusPonens said:
I took the harmonic balancer off my 93 sc to find that the crank keyway chewed into the keyway on the balancer. the crank keyway appears to be only 1/8 to 1/4 inch long, while the keyway on the balancer runs the length of it. It doesn't make sense that such a small key would be responsible for holding the weight of the balancer and all stress behind it. First off- does my problem lie with this crank key not running the full length?

obviously i need a new balancer. the key rotated on the balancer about 10 degrees. Any suggestions on how i can prevent this from happening again?
thanks
Janine.

The crankshaft keyway runs nearly the full width of the balancer hub. Sounds like you need a new balancer, new balancer bolt and a new key. Here is a link showing how to replace the balancer that may be helpful.


http://www.mn12performance.com/mn12how-to/BHJ/BHJ-install.html

David
 
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I think with the combination of the press fit balancer and the crank bolt, the key is just a small factor in holding the balancer from rotating. If it turned and chewed up this key, there was something wrong with it anyway. I put a used balancer on mine to shake down the engine, and its a crap shoot, but I ended up with a nice tight fitting balancer that doesnt wobble.
 
after consulting a few professionals and forcing them to actually look at the engine, we discovered what really happened:

at first i was told that my crank was damaged to the point of no return... but when the old balancer was compared to the replacement we discovered that the balancer i was looking at, with the long keyway and tiny stub of a key... was really only part of the balancer. the balancer and key had broken off so cleanly (and rubbed together for quite some time) that the two halfs of the balancer snout appeared to never have been together.. it broke off flush with the block and actually blended in with it, so no one suspected that the snout of the balancer was supposed to be longer.. especially since i was told not to special-order the balancer unless i was SURE that my crank wasn't F-ed. After violent chiseling it and the rest of the key was out. My crank was fine, and a new balancer and key was installed.

now for the drama:
the motor was rebuilt for FMC at the end of 2004- right before i owned it- and since only had about 3-4k miles on it. (the car has been sitting) that distroyed balancer was CLEARLY distroyed for a long time. this is the most disgust i've felt for the Ford Motor Company in... well, ever. Whoever rebuilt it didn't notice this problem either- or chose to ignore it. this problem could have caused the engine to blow in the first place. THAT'S MESSED UP. I still love my Ford, but FoMoCo is on my ~~~~list right now. for damn good reason.
 
Ford doesn't actually do the rebuilds, they sub contract that work out to other shops. Buying a rebuilt motor from Ford is a crap shoot at best. The only good thing about it is they will warrant the motor.

David
 
I doubt that the rebuilder installed a new balancer on the crank. Ford replaced my engine back in the late '90's with a crate motor, but reinstalled the original balancer (I found out later when it broke). This isn't a problem on most cars, but because of the poor design of the SC balancer it is a definite no-no... My suggestion is to replace the key and invest in a BHJ balancer. It costs about twice as much as a stocker, but you won't have to worry about it breaking. In the long run you will come out ahead (believe me, i broke 3 stock units before getting my BHJ).
 
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