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Harmonic Balancer


Gone but not forgotten
Jan 30, 2001
Hermosa Beach, CA
1987 Z51 Silver Coupe
How do ya check it?

I mentioned in my report on my nightmare-ish trip to Mecca that I had a noticible vibration at certain rpms.

Well I just put the Vette away for the night and decided to sit there and monitor the tach for awhile at various rpms to see exactly where the vibration starts. I'm starting to get a very mild "harmonic" type of vibration at about 1900 rpms and it grows progressively more pronounced at higher rpms. I stopped at 2500 because I didn't want the neighbors complaining ;), but I know it grows until at least 3600-3700 rpms, and then the vibration is worsened by the different road surfaces and other rotating pieces of equipment on the car, so this period in the garage was the first time I was able to feel it without other interference.

How can you tell if the balancer is in bad order, other than a visual inspection with it off the engine?

Well BroKen if you do a visual inspection I've found where they start to spit the rubber out. For lack of a technical term. They actually have a buldge and begin to separate.

Of course C4's are not my expertize :D

I had to replace mine to From what I got from the mechanic is that you'll fiind theres a lot of vibration throughout the car AND most importantly if you remove it to check it or replace it they do have to be lined up somehow I guess they are not just a bolt it on away you go thing (This is the reason why I had to replace mine the prior owner removed it and put it back out of line and it vibrated till it exploded... thats all I know
Harmonic Balancer- quick check


Bud is correct, if you see the rubber liner bulging out, the balancer has definitely spun and needs to be replaced. But that bulging liner is not always apparant. A sure way to determine if you've got a bad harmonic balancer is to check your timing with a timing light. If the timing has changed dramatically then the balancer has spun. The severe vibrations you're experiencing is a good indicator of an out of balance condition.

Check it out,
Indicate it

Hi there,
At the shop, we have to install a dial indicator to see just how far out it is, as .005 is as far as we can go.
If you have to replace it, a Fluiddampr is an excellent choice, as GM performance parts sells these for racing applications.
Best to you, c4c5
Re: Indicate it

c4c5specialist said:
...a Fluiddampr is an excellent choice, as GM performance parts sells these for racing applications.

Thanks c4c5, I am going to use nothing but the best when I start getting into it. ;)

PS, glad to see yer still with us occasionally. :upthumbs Say hi to chick.)

Could Be

I had a friend with a balancer that went bad, and he had to have it checked with the dialer. He replaced it with a fluid dampr and has never had another vibration. I have seen the rubber shift and they do go bad, let us know how you make out.
I had a very similar problem once upon a time ('82 Z28), turned out to be a cracked flywheel. Just a thought.....

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