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Topic: Vibration @ 2K

in Forum: C3 Engines


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Vibration @ 2K

Posted: 2/25/07 4:40pm Message 1 of 20
bytor
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Simpsonville, SC - USA
Joined: 1/21/2007
Posts: 85
Vette(s): 1978 25th. Silver Anniversary Edition 350 L-82 Stock

I have been troubleshooting a pesky vibration that starts around 2000 RPM.  I have disconnected all the belt driven accessories, not the problem. The previous owner replaced the harmonic balancer and engine mounts.  I happen to be under the car looking for an exhaust leak and noticed this……

 

 

  

The engine mount bolt was touching the fuel pump.  Not just touching but putting considerable pressure on the fuel pump.

 

 

 

I installed a spacer and this is what is looks like now and the vibration is much better now but not gone completely.  My next suspects are a misfire or clutch/flywheel balance problem.




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Vibration @ 2K

Posted: 2/25/07 4:57pm Message 2 of 20
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Gunslinger
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
You really need to define what you mean by "vibration". That can mean a lot of things. Does it sound like the noise is coming from the engine? Does it sound metallic? Is it a rapping kind of sound? Is it scraping?

If it's at a specific speed, it could be wheel balance. Do you feel it through the steering wheel or through the seat? Through the steering wheel it's front of the car related, like the tire balance...if through the seat and floor, it's coming from the rear.

That bolt impinging on the fuel pump should not be doing that, but it could be the source of your problem or it could be unrelated and you just found it as a coincidence. Either way, it should be corrected. You definitely don't want the fuel pump to start leaking or break from that. Get that fixed and see if your problem is taken care of.


Vibration @ 2K

Posted: 2/25/07 5:14pm Message 3 of 20
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Looks like someone used a starter bolt for the mount.

IF the engine mounts are loose, they will contribute to a vibration under power. I do agree with Bruce, tho...that's probably not what you are looking for.
Is this a hard vibration, or a light one?
Is it engine speed related, or road speed related?
Does it go away if you put the trans in neutral?


Joel Adams
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Vibration @ 2K

Posted: 2/25/07 5:33pm Message 4 of 20
gellisvette
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PERRYSBURG, OH - USA
Joined: 4/23/2004
Posts: 317
Vette(s): 1975 T-Tops,Lite Custom work,Many engine mod. 700R4 trans. body is shaved,17" wheels bf goodrich g-force tires,heavy sway bars front&rear rack&pinion steering,550 slolom springs with gas shocks.
Damb, someone else is chasing a ghost also! I have owned my vette for many years and have been chasing a vibration for as long as I have owned it. I have changed everything under the sun. Infact I have even considered selling it because of the vibration and only for that reason . The vibration comes in at about 2000 rpm and smooths out after 2500 to 3000. It seems like a harmonic thing not a metalic thing.I will be checking the motor mounts next after seeing your photo. It's a seat of the pants thing. People riding in the car say they don't feel it. When I say it smooths out- it maybe because it just feels that way. Nothing has worn out and I keep hopeing something will so I can put my finger on it. My heart go's out to you, because it's driving me nutsWits%20End.


Vibration @ 2K

Posted: 2/25/07 6:23pm Message 5 of 20
ranger3
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North Charleston, SC - USA
Joined: 3/20/2004
Posts: 4176
Vette(s): 1975 L48 AT AC T-top
Does the car have to be moving or will it vibrate with the car in park or neutral (manual) with the engine revved to 2000rpm. If it is high frequency while being driven I would look at the tansmission, drive shaft and half shafts. Those are affected by harmonic imbalances. If it does it sitting still then it is in the engine, flywheel, clutch.


Vibration @ 2K

Posted: 2/25/07 6:31pm Message 6 of 20
bytor
Former Member
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Simpsonville, SC - USA
Joined: 1/21/2007
Posts: 85
Vette(s): 1978 25th. Silver Anniversary Edition 350 L-82 Stock

I feel the vibration when the car is parked.  Engaging and disengaging the clutch doesn’t change the vibration.  I feel it in the steering wheel and gearshift.  It starts at 2000 rpm and begins to go away around 3500.  One thing worth mentioning, the previous owner said when he got the car, he had to replace the oil pan because it was dented in.  The person that owned it before him must have bottomed it out.  The pan was replaced along with the oil pump.  The impelled fuel pump was definitely contribution to the vibration but the search continues.  It’s good to know I’m not the only one experiencing this.




Vibration @ 2K

Posted: 2/25/07 10:06pm Message 7 of 20
deeboy59
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visalia, CA - USA
Joined: 10/27/2006
Posts: 641
Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition

The vibration on mine,  which,  by the way, has had me stumped for a while now,  seems to come and go.  Sometimes its ther  and you know it.  And then you'll drive it and and think that its gone.  and this will happen going down the same road,  same speed, etc.  Lately I've been think'n misfire in the igntion,  or EMI to the EST (thats electro magnetic interference  to the electronic spark timing) from the plug wires maybe?   Any thoughts ?




Vibration @ 2K

Posted: 2/26/07 10:41am Message 8 of 20
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dwright
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Victor, NY - USA
Joined: 7/12/2004
Posts: 6841
Vette(s): 2004 Commemorative Edition Coupe, Auto w/HUD. 13K miles in 2015. Sold 1982 Red Coupe
If it is engine speed related, I would check the harmonic balancer.


 
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Vibration @ 2K

Posted: 2/26/07 11:04am Message 9 of 20
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.
I vote for the harmonic balancer also. Those things have a history of going south on you.
Dave



 

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Vibration @ 2K

Posted: 2/26/07 11:15am Message 10 of 20
Okie Dude
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Eastern Oklahoma County, OK - USA
Joined: 1/3/2006
Posts: 1560
Vette(s): 1980 Black L48 T-Tops
Could it be possible that the big dent in the oil pan may have put the crank out of balance?  Did it do any damage to the flywheel such as perhaps knock off a weight?

Just reaching at straws here...



in Forum: C3 Engines


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