Vibration on the 67 starting at 3500rpm "help"

[jims427400]

Well I've really babied the 427 since I got it this year.Today before I store it for the winter I thought I'd really make some noise and take a little tread off of the coker redlines.As I approach 3500rpm I start to get vibration from under the car and it gets worse as I increase rpm's.I dont think I could get even close to 6000 red line.I've allready done the search thing on vibration but didnt find anything.Car is a numbers matching engine so where should I start.I know it could be many different things but you all have been so helpfull in the past.Thanks again everyone, Jim

 

[BarryK]

does it feel like it's coming from the front, the rear? Is your impression it's from the motor or more from the suspension?

could be any number of things and others MUCH, MUCH more knowlegable than me will chime in (easy to do since I know basically nothing) but maybe a bent fan blade on the motor, or could be somewhere in the suspension so it increases as you speed up (higher rpm's), rear bearings, tire out of balance......

can you help us out a bit by trying to pinpoint it down even a little more. A "vibration" is a bit vague.

 

[jims427400]

Barry,
I think its coming from between the center and rear of car. I have little experience w/ this year car.I had a 74 that ate up the bronze bushings that went between the engine and trans do to a harmonic balancer problem.Hoping thats not the problem w/ this.Maybe its time for some professional advice. Thanks..

 

[BarryK]

well, if you think it's coming from the center or rear of the car iI'd get the car up in the air and check everything that can be affected by an increase in rpm's.
The driveshaft, rearend, halfshafts, & bearings. Make sure the tires and wheels are balanced correctly.

that's all I can think of but i'm sure others will chime in soon enough with other ideas.

 

[youwish2bme]

Did you burn em down? If you smoked the tires you could have rotated the tire on the rim and now the tire is out of balance. Not a big deal just something you need to be aware of... Dave..

 

[Sky65]

Does the vibration occur in neutrall and you just wind it up or do you need road speed? Does it do it in all gears? Does it need to be under load?

 

[jims427400]

Sky
Thats a great point.I didnt try it in nuetral.Stay tuned !!

 

[JohnZ]

Drive it up to the speed where you have the vibration, and put it in neutral, allowing the engine to drop to idle; that will tell you if it's speed-related or engine-related, and we can go from there.

 

[vett boy]

Number one cause ''u'' joints,number two tires and or balance.90% chance -good luck and post your findings.

 

[78Vette-SA]

Drive it up to the speed where you have the vibration, and put it in neutral, allowing the engine to drop to idle; that will tell you if it's speed-related or engine-related, and we can go from there.

Had a similar problem with my 63. Was annoying to say the least. Did it just sitting or in gear. At speed if I dropped it in neutral it went away so obviously it was in the front.

I pulled the clutch and flywheel (which had been surfaced and a new ring gear put on but not balanced) and had the clutch and flywheel balanced as an assembly. Problem gone!