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Topic: May Have Found Root Cause to Vibration

in Forum: C3 Engines

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May Have Found Root Cause to Vibration

Posted: 3/27/10 4:09pm Message 1 of 5
jp75vette
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Bloomfield Hills, MI - USA
Joined: 6/29/2008
Posts: 199
Vette(s): 1975 Corvette coupe, 4 speed manual, 383 ci 9.5:1,Edelbrock dual plane Air Gap intake, Alum Heads,Comp Cam, roller Rockers, PS,PB,Tilt
I pulled my old engine to get ready to insatll the new 383.
 
In the past, I had vibration at approx 1500 RPM and also 1t 3-3500RPM.
 
I pulled the flywheel and noticed that the alignment dowel was missing.
 
That puts two possible causes for the vibration.
 
1. The flywheel was not mounted in the 'dowel' location, meaning that the balanced flywheel was off location to the flywheel.
2. The dowel was missing and this would mean that some mass was missing causing and inbalance.
 
Here is a photo of the end of the crankshaft and the missing dowel.



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May Have Found Root Cause to Vibration

Posted: 3/27/10 6:51pm Message 2 of 5
ranger3
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North Charleston, SC - USA
Joined: 3/20/2004
Posts: 4176
Vette(s): 1975 L48 AT AC T-top
Very interesting. It certainly seems that would set up a vibration.
 
Scott


May Have Found Root Cause to Vibration

Posted: 3/28/10 9:28am Message 3 of 5
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aceinthehole
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Manteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed
I don't have any experience machining motors but that is highly suspect. You'd think the bolt pattern would maintain the alignment though, and the amount of weight missing would depend on wether the aligning dowel were hollow or solid Confused. it would be interesting to know what could cause a motor to do that though.


Jimmy B.
Just can't wait to get on the road again.

 
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May Have Found Root Cause to Vibration

Posted: 3/28/10 6:12pm Message 4 of 5
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wetvet
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Lake Oswego, OR - USA
Joined: 10/17/2003
Posts: 558
Vette(s): 1972 Steel Cities Gray T Top. Original Owner, Original Paint and Interior. The running gear has been rebuilt. only 250,000 miles on the clock..
You might want to check the balance of your drive shaft, and half shafts. The bolts should keep the flywheel in place(if they are torqued correctly)


 
(click to see a larger image)


"It Takes A Little Longer To Do It Right"
"It Takes A Lot Longer To Do It Again"

  

May Have Found Root Cause to Vibration

Posted: 4/10/10 8:12am Message 5 of 5
gsfowler
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N. Scituate, RI - USA
Joined: 2/24/2006
Posts: 30
Vette(s): 1971 roadster 4 speed blue with white top 1990 roadster 6 speed white on black
when I did my body off I used OEM rubber mounts ,in a short time I had minor vibrations .after talking to a frend about this he said try changing mounts [starting with tale shaft ] using urathane, I did and what a differance. I then changed the trailing arms bushing and then the front end, made all the diffrence in the world.you might wount to look at what is in your car now ,you might have the same situation .anyway good luck 


in Forum: C3 Engines


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