Harmonic damper is wobbling

[Mark A.]

I have a vibration in my newly restored 69 427 390 hp coupe. The engine is smooth up until a little over 2000 rpm, then it has a vibration. I believe it is coming from the damper. It has a wobble at low rpm, but straightens out at higher rpm. I have never seen a damper wobble. What could be causing this? Car Quest balanced the engine. I would think they would have noticed if the crank was bent. Any suggestions? Thanks, Mark

[Joe L.]

Re: Harmonic damper is wobbling

I have a vibration in my newly restored 69 427 390 hp coupe. The engine is smooth up until a little over 2000 rpm, then it has a vibration. I believe it is coming from the damper. It has a wobble at low rpm, but straightens out at higher rpm. I have never seen a damper wobble. What could be causing this? Car Quest balanced the engine. I would think they would have noticed if the crank was bent. Any suggestions? Thanks, Mark

Mark-----


I would suggest that you have a failed harmonic balancer. The elastomer component may have deteriorated. However, I'm surprised they didn't catch this when the engine was balanced. In any event, if the balancer "wobbles", I expect that this is your problem.

A new balancer was available until a few years ago under the original part number of GM #3860008 but it's now discontinued. Reproduction/replacements are available, though. Or, you can have yours rebuilt.

[Gary R.]

Re: Harmonic damper is wobbling

I used Damper Doctor in CA to rebuild my original 72's 350. I did have a problem getting mine back though, it took 3 trips and only because I took pictures on mine before I shipped it. They do a lot of exchanges and the ones swapped were beat up. Once I got mine back it was fine.

[Joe L.]

Re: Harmonic damper is wobbling

I used Damper Doctor in CA to rebuild my original 72's 350. I did have a problem getting mine back though, it took 3 trips and only because I took pictures on mine before I shipped it. They do a lot of exchanges and the ones swapped were beat up. Once I got mine back it was fine.

Gary-----


If you're talking about the balancer for a 1972 base engine I don't think I would have gone to the trouble of having one rebuilt. I believe the SERVICE balancer, GM #12551537, is identical to the original. You might even be able to find an NOS GM #6272221 around which was the original balancer. In my opinion, a factory-manufactured balancer is preferable to a rebuild.

[Gary R.]

Re: Harmonic damper is wobbling

Hi Joe,
Yes it was the base eng damper but I wanted to do this for 2 reasons.
1- I still wanted this one back, it was near mint condition compared to what I saw and they returned.
2- I wanted to see how this service was in case I have others, like my 8" L-82 damper to rebuild.
I was pleased with the final product but it was a hassle to get mine back. I wouldn't have minded but I did call before hand to make arranements to get this one back.

Gary