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Discussion Starter #1
Does anyone have advise for me??? I had a 1966 mustang 289 ngine rebuilt. And since the rebuild, I get a surge and vibration between 40-50MPH, and will decrease over 50MPH. My mechanic thinks it could be the harmonic balancer, basically everything else has ben ruled out allignment etc...The engine was rebuilt by a big engine restoration company. Could they have not balaced something correctly when putting the engine back together??? I have a warranty till 50K.
Long story short anyone had these experiences and how were you able to fix it.
Any info will be of great value to me, since I'm not too experienced with this.

Many Thanks!

Jason
 

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Which flywheel did you use? What is the condition of your harmonic balancer? Is the balancer original?aftermarket?
 

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Two more questions?
What accessory pullies do you have? At idle, do any of the belts/pullies look like they are not turning correctly?
 

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Discussion Starter #5
harmonic balacer

Which flywheel did you use? What is the condition of your harmonic balancer? Is the balancer original?aftermarket?
I'll have to check on the flywheel uses. The harmonic balancer is the original and I assume the condition is/was good, I got no recommendations to change it.
I thank you for your reponse any help is appreciated.
 

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Discussion Starter #7
66 mustang harmonics

Two more questions?
What accessory pullies do you have? At idle, do any of the belts/pullies look like they are not turning correctly?
As far as I can tell and a mechanic checked it too, all the pullys seem to be working fine. thecar has all its original smog equipment, plus ac.The car idles smooth, its just when it gets going above 40 mph the surging and vibration starts.
 

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Well, if the pullies are not wobbling, the harmonic balancer could have spun and is now out of balance. My original broke, but the original balancers can get out of balance. The rubber will wear out on them.
 

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Discussion Starter #9
Well, if the pullies are not wobbling, the harmonic balancer could have spun and is now out of balance. My original broke, but the original balancers can get out of balance. The rubber will wear out on them.
Thanks i will ahve my mechanic look at that :)
 

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Discussion Starter #12
mustang 66 GT

Did you check your tires, drive shaft,
motor mounts, and welcome to the site.
Thanks for your response! All the above mentioned parts have been replaced. I hoping this is something that should follow under the warranty issue. I had the engine and tranny rebuilt by Jasper and have heard good feedback on their work. My mechanic did do some tweaking yesterday with weights and it seems to have improved the problem slightly. But I spent 4K rebuilding the engine and tranny and want it to be right. I basically have ruled out all other problems that can cause this so i think it is down to the haronics.
Thanks for your input man, it is appreciated.
Jason
 

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Discussion Starter #13
66 mustang GT

Did you check your tires, drive shaft,
motor mounts, and welcome to the site.
Yes, have eliminated all those issues, had the front end rebuilt and alligned,as well as new tires. Motor mounts are new.
It seems like it is down to the harmonics.
Glad to find this blog and appreciate all the feedback from fellow mustang lovers.
Jason
 
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