C3 Vibrations
Thread Starter
Pro
Joined: Jan 2002
Posts: 624
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From: Marietta ga
C3 Vibrations
I just recently had my motor rebuilt. It was balanced and blueprinted among many other things. It also recieved pistons, cam, lifters, bearings, intake,fuel pump, high volume oil pump, harmonic balancer, and fan clutch. When it is in neutral with the clutch in or out or if i am driving , there is a vibration and a noise @ 2500 RPM and up. It hums soft and then louder and softer, back and forth. I was thinking a bearing in the transmission (Munice M21) or somthing else in the drive train? Anybody have any good ideas. Oh yeah it never did this before the motor was rebuilt. :chevy hope it is not the motor?????
Drifting
Joined: Oct 2000
Posts: 1,825
Likes: 56
From: Shawano WI
Re: C3 Vibrations (Cory1970)
I would check to make sure the throw out bearing is sitting on the fork propery. If you did not get it sitting correctly over the spring clips it may be cocked and riding against the pressure plate on one side and causing a vibration and noise.
Safety Car
Joined: Jan 2000
Posts: 4,143
Likes: 0
Re: C3 Vibrations (Cory1970)
Good, good, good, -good vi-bra-tion, ....I'm talkin' 'bout good vibrations. :jester
Sorry - just couldn't resist the Beach Boys tune ! :lol:
...mine vibrates, too - at 55mph & at 75mph+ ....but me thinks it's worn treads & poor balancin' :yesnod:
Sorry - just couldn't resist the Beach Boys tune ! :lol:
...mine vibrates, too - at 55mph & at 75mph+ ....but me thinks it's worn treads & poor balancin' :yesnod:
Instructor
Joined: Oct 2001
Posts: 224
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From: Austin TX
Re: C3 Vibrations (Cory1970)
I had a similar problem....Thought I blew something in my motor. Just an idea to check the ac and ps mounts as the ac bracket is cast.....my 77 is atleast. Just an idea. :smash:
Thread Starter
Pro
Joined: Jan 2002
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From: Marietta ga
Re: C3 Vibrations (Cory1970)
the vibrations have continued... and have gotten worse. AT idle it is hard to feel. You can definately feel it at 2500 then it seems to stop. Then at 3500 it seems as if it is about to blow up. I realy mean it, it is about to shake apart. Any ideas......... these are not such goooooood vibrations......
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: C3 Vibrations (Cory1970)
Tell us more about what you have and haven't checked. What items have you eliminated? Sounds like a heavy sort of vibration.
What engine do you have?
Has your fan lost a blade?
Could it have the wrong flywheel installed?
Have you discussed this with the shop that built your engine?
I dont really think that it is caused by a problem with your engines internal rotating assembly.
Can you provide any more information?
What engine do you have?
Has your fan lost a blade?
Could it have the wrong flywheel installed?
Have you discussed this with the shop that built your engine?
I dont really think that it is caused by a problem with your engines internal rotating assembly.
Can you provide any more information?
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Burning Brakes
Joined: Oct 2001
Posts: 860
Likes: 40
From: Woodforest
Re: C3 Vibrations (Cory1970)
You mentioned that the vibration is there whether you are driving or not. If this is the case, the issue would seem to be the motor. You also mentioned having a new harmonic balancer. First thing I would do is replace this with another one and see what happens. Past that, would have to be an internal issue with the crank. I would take it back to the shop that rebuilt it and show them the problem.
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: C3 Vibrations (Cory1970)
what makes a flywheel or balancer externaly balanced :confused:
The flexplate on my 383 has a weight welded to the outer most edge next to the ring gear. If I can remember correctly, it is about ~5/8" wide by ~10" long. The size of this weight may vary from one flex-plate to another depending on amount of weight needed but most should be similar in size.
[Modified by MIKER, 4:29 PM 5/18/2002]
Heel & Toe
Joined: Apr 2002
Posts: 20
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From: Billings Mt
Re: C3 Vibrations (MIKER)
It's a C3 don't they all vibrate. My does at about 2500 rpm and 3500 rpm but I have 30,000 miles on the motor. I am rebuilding my rear end after lots of advice from you guys and hope to be running again in about two weeks.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Re: C3 Vibrations (Cory1970)
Maybe it has the wrong harmonic balancer or wrong flexplate (or both) installed.
Or ... Maybe the harmonic balancer's outer ring has slipped. Check your timing with a timing light ... if you have a lotta trouble (timing mark is WAY, WAY off) ... and APPEARS as though you need to turn the distributor a bunch ... then maybe a slipped balancer's the culprit. New ones can fail.
Or ... Maybe the harmonic balancer's outer ring has slipped. Check your timing with a timing light ... if you have a lotta trouble (timing mark is WAY, WAY off) ... and APPEARS as though you need to turn the distributor a bunch ... then maybe a slipped balancer's the culprit. New ones can fail.
Thread Starter
Pro
Joined: Jan 2002
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From: Marietta ga
Re: C3 Vibrations (rscucan)
true, most c3's vibrate, but mine sounds like it is about to come apart @ 3500 RPM
:cheers:
It's a C3 don't they all vibrate. My does at about 2500 rpm and 3500 rpm but I have 30,000 miles on the motor. I am rebuilding my rear end after lots of advice from you guys and hope to be running again in about two weeks.
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: C3 Vibrations (MIKER)
I suppose that it is possible that they could have installed a flex-plate that was meant to be used on a 400 or 383.
I'm sure that an externally balanced flywheel has some sort of visual cues as well.
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: C3 Vibrations (Cory1970)
I think what you need to do is find out what you have first.. Your engine needs an exterally balanced flywheel and dampener if it is a stroker (383 ). (only those and SB400's use them) Both are recognizable. A friend of mine put a new 350 from auto in his old truck. He thought his old motor was a 350 and used the flywheel and balancer.....NOT!! It was a 400 which also uses external balance. Anyway,, his truck vibrated big time at certain speeds. He tried changing everything over a period of time. Then somedody told him that his old motor was a 400 and had a different flywheel and balancer... Bingo.... Smoothed right out...
[Modified by silvervetteman, 4:30 AM 5/20/2002]
[Modified by silvervetteman, 4:30 AM 5/20/2002]
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Re: C3 Vibrations (Cory1970)
Cory,
If you balance the motor, then you should ALWAYS have the flywheel balanced. IF you are using the same [as before the rebuild] DAMPER Pulley, that shouldn't be a problem.
If you balance the motor, then you should ALWAYS have the flywheel balanced. IF you are using the same [as before the rebuild] DAMPER Pulley, that shouldn't be a problem.
