Engine vibrates at high RPMs

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Jul 14, 2006 | 11:13 PM

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

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From: Cruising somewhere in St. Louis, Missouri

Engine vibrates at high RPMs

When I do push it to say maybe around 4000 RPMs the engine has a vibration, I can feel it thru the Stick shift. Can this be a Harmonic Balancer issue?

Thanks in Advance,
Jim

Jul 14, 2006 | 11:21 PM

...Roger...

Race Director

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From: Dayton, Ohio

Check water pump first

Jul 14, 2006 | 11:26 PM

Greg

Just another Corvette guy

Joined: Feb 1999

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From: Palm Springs, CA.

....and your fan and your harmonic balancer.

Jul 14, 2006 | 11:36 PM

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

Posts: 2,101

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From: Cruising somewhere in St. Louis, Missouri

I have no fan... replaced with electric one....water pump works so don't know how to check that one?

but i might give me an excuse to buy a chrome one

Last edited by luerja; Jul 14, 2006 at 11:39 PM.

Jul 14, 2006 | 11:40 PM

...Roger...

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From: Dayton, Ohio

Quote:

Originally Posted by luerja

I have no fan... replaced with electric one....water pump works so don't know how to check that one?

I was talking about bearing in the water pump if it is loose it will cause the fan to wobble but thats probably not you problem.You can still check the bearing to see if it is tight by pushing on pulley.

Jul 15, 2006 | 12:10 AM

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

Posts: 2,101

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From: Cruising somewhere in St. Louis, Missouri

I just know that if a water pump bearings are bad the water will leak out of it.. Mine doesn't

HHHmmmmmm?????

Jul 15, 2006 | 12:27 AM

71-Triple Blk

Heel & Toe

Joined: Jun 2006

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I had something similar but it was my tansmission mount - I went trough everything before that $11 part. Just sharing my pain.

Jul 15, 2006 | 12:47 AM

...Roger...

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From: Dayton, Ohio

Quote:

Originally Posted by luerja

I just know that if a water pump bearings are bad the water will leak out of it.. Mine doesn't

HHHmmmmmm?????

Thats the seal that keeps the coolant in the bearing can still be worn .Still probably not your problem being that you dont have fan.Is this a new problem or has it been there for awhile ?

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Jul 15, 2006 | 02:02 AM

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

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From: Cruising somewhere in St. Louis, Missouri

I kind of think the problem was there before i purchased the car... It’s a little more noticeable since the supercharger is on now.

Transmission mount might be an option? it does come right thru the 4 speed shifter

Jul 15, 2006 | 08:56 AM

#10

...Roger...

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From: Dayton, Ohio

Quote:

Originally Posted by luerja

OK and wow-supercharged-that adds a new piece to the puzzle-yes get your mounting in order and work from there-sounds like your mods are a good starting point and what your mods have effected--harmonic balancer-- -clutch---pilot bushing--headers hitting frame --exhaust bolted to trans mount wrong--try to isolate if it is engine or drivetrain--torque on or torque off---I whittled one down to an out of balance crankshaft-it was a 78 -L-82 with 11000 miles and the guy was the original owner and had never been touched- must have been a Monday balance job on crank

Good Luck

Jul 15, 2006 | 10:37 AM

#11

rihwoods

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Are you sure it's engine related ? What happens if you rev it to 4000 rpms in neutral ? Reason I ask,I just replaced all spring clips/washers on my shift linkage as I had a rather moderate vibration in the shifter at 80 mph(78 SA).....smooth now..

Jul 15, 2006 | 11:05 AM

#12

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

Posts: 2,101

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From: Cruising somewhere in St. Louis, Missouri

Quote:

Originally Posted by rihwoods

I was just thinking about that last night about 2:30am

.... It doesn't vibrate when in Idle.....So it must be Drivetrain related. It drives just fine with no vibration until it hits the higher revs..

Jul 15, 2006 | 11:19 AM

#13

Mild2Wild

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Joined: Jul 2006

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From: Narcoossee Florida

Get the car to a high speed and take it out of gear and see if it still has it.They may have the wrong flywheel on it.I just got a vette and it had the wrong flywheel. I found this plate they make that bolts up to it to add more weight.. What motor do you have?

Jul 15, 2006 | 11:44 AM

#14

rihwoods

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Quote:

Originally Posted by luerja

I was just thinking about that last night about 2:30am

.... It doesn't vibrate when in Idle.....So it must be Drivetrain related. It drives just fine with no vibration until it hits the higher revs..

Mine had me baffled..was thinking all kinds of things...then the 1st/2nd linkage slipped off the shift rod in a parking lot...I fixed that one..and vibration was less,but still there...that led me to the rest...BTW..reverse is a pita to do...I ended up dropping linkages out of way just get that one...be sure to use correct clips/washers..

If you don't have a clunk associated with vibration..ie..getting on it,letting up,chances are your suspension bushings/u-joints are ok...

Hope this helps...
Rich

Jul 15, 2006 | 11:44 AM

#15

marshrat99

Melting Slicks

Joined: Aug 2003

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From: Dayton Oh

Other possibilities include out-of-balance tires, shocks, U-joints.

Jul 15, 2006 | 12:09 PM

#16

luerja

Thread Starter

Melting Slicks

Joined: Dec 2004

Posts: 2,101

Likes: 3

From: Cruising somewhere in St. Louis, Missouri

Quote:

Originally Posted by Mild2Wild

Get the car to a high speed and take it out of gear and see if it still has it.They may have the wrong flywheel on it. I just got a vette and it had the wrong flywheel. I found this plate they make that bolts up to it to add more weight.. What motor do you have?

I have done that and it has gone a way, Not exactly sure on the motor? It was in the car when I purchased it, there are many threads by me from the recent past that tried to figure that question out. All we can up with was a build 350 (more than likely a 383), it is a GM built motor with Fast Burn Aluminum heads. GM doesn’t have the records on the engine but do admit it was more than likely built by them or someone took all their parts and put one together.

Quote:

Originally Posted by rihwoods

The car drives great other than the vibration…No clunks and the tranny shifts just fine in all gears.

Quote:

Originally Posted by marshrat99

Other possibilities include out-of-balance tires, shocks, U-joints.

Thought about that too… but it will glide smooth when tranny is not enguaged

I'm fairly certain it has to do with the Clutch, flywheel, pressure plate area. I am not an expert and have never replaced a clutch before but I am thinking it is not centered perfectly and gets more pronounced at higher revolutions? Could this be the case?

Thanks for all the suggestions...this forum is great

Jim

Jul 15, 2006 | 12:17 PM

#17

rihwoods

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Well...if the pilot bushing in flywheel is worn,that could be part of the issue...but I took my 78 original clutch to 112,000 miles before it slipped and needed replacement.....no vibration,though...and there were pieces falling out of the metal spring do dads on the disc..

Pulling tranny will sure make doing those linkage clips easier...

Jul 15, 2006 | 06:23 PM

#18

66jack

Team Owner

Joined: May 2006

Posts: 37,654

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From: CA

Check on this

While restoring my 66 i decided out of curiosity to have the Driveline checked to see if it needed to be balanced...man did it ever...the weights when it was done originall were 180 degress out..
Although i am not in a position to see if vibrates or not i ASSume that technology today is way better than the later..
So mabey that might be a source of your vibration
just a thought

jack

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