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Discussion Starter #1
If you had a situation where your car had a vibration every time the engine speed reached 2,500 RPMs ... Where would you look first.

Speed of the "Car" doesn't affect the vibration, so I've pretty much ruled out "Tire" ... "Drive Shaft" ... Etc.

It's a 4 speed car so it's real easy to just run the RPMs to 2,500 in any gear to get the same vibration ... this problem is definately associated with "Engine Speed" ... I'm not sure it ever goes away at any RPM ... My sense is ... the vibration just increases in frequency as RPM increases to the point that it may "seem" a bit better at higher RPM.

It's a new (rebuilt) V8 engine and was balanced ... Well, I paid to have it balanced anyway.

Engine seems to have all the power it's suppose to and there are no "fouled" plugs indicating a major "Tuning" problem.

It's making the car a pain in the A$$ to drive and it seems to me it's getting a bit worse as time goes by.

Any thoughts??

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Larry Madsen
Las Vegas Nevada



<font size=-1>[ This Message was edited by: monstermach on 1/20/02 10:11pm ]</font>

<font size=-1>[ This Message was edited by: monstermach on 1/20/02 10:17pm ]</font>
 

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I just had a similar problem and I discovered my harmonic balancer was wobbling. I replaced it with a new Ford balancer and now I have a vibration at 4000 rpm. I guess I am in the same boat as you.
 

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I had a similar problem with my 66 coupe, the rubber part of the driver side engine mount was cracked. Visually it was barely noticeable, but the problem was gone after I replaced it. That was after trying 2 different harmonic balancers.
 

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Along with checking motor mounts and balancer you should also check to make sure all accessories brackets and pulleys are tight, Alt. P/S, A/C, etc...
 

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Did you check the Archives?

www.fordmuscle.com/archives/2000/06/vibrations/index.shtml

JL

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Jim Langley

Technical Editor

Fordmuscle.com

'65 Mustang GT, 289 (Warp 65)

'92 Mustang, 5.0 T5Z (Green Machine II)



<font size=-1>[ This Message was edited by: FasterDamnit! on 1/20/02 11:55pm ]</font>
 

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Discussion Starter #6
Thanks Jim ... I had missed that section.

It is However leading me to realize my worst fear.

This engine is only a few months old and has always had a vibration. I had to pull it once for vibration ... and a massive oil leak ... rear main seal on a brand new rebuild


At that time I took the engine to the shop that assembled the shortblock for me ... they checked the balance on the flywheel and found it ot be "Off" ... they made some corrections and the engine seemed a bit smoother ... they also installed a heavier main seal.

At this time ... the engine still has a vibration and still leaks (leaks less, but still leaks) I have been told that if a crank is vibrating ... the seals will usually leak as well ... (as in, can't seal with the vibration going on).

I will also add .. this was an aftermarket crank ... not an existing factory crank so it had never been prviously balanced or in an engine ... virgin crank, possibly making the balancing process more extensive. Oh ... it's an internally balanced engine for what that is worth.

I checked the thing while sitting still in the driveway ... as RPMs climb to 2,500 you can feel and hear the vibration ... so I am fully convinced it is engine related. I'll get the floorjack and jack the engine up a bit to see if motor mounts are pulling apart or doing anything abnormal.

Thanks ... I'll still take all the input I can get guys


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Larry Madsen
Las Vegas Nevada



<font size=-1>[ This Message was edited by: monstermach on 1/21/02 12:21am ]</font>
 

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Does the vibration exist when the car is in neutral or just at speed?
 

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Discussion Starter #9
Jimmy ... 4 speed ... and as in my previous reply ... you can hear and feel the vibration just sitting in the driveway, as the RPMs get to the range in question.
 

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Soory, just seen your post. We must have been typing at the same time. I'm hoping for your sake that it is an off balance flywheel. If not, try a balancer swap next for assurance. I know YOU have another balancer around. If it's still there, try the acc, for off balance. Never know, bad water pump. Lastly you might be right, it will probobly be the crank.
 

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Discussion Starter #11
Question ...

Assuming it's the Rotating Assembly itself ...

Would we expect the vibration to get noticeibly worse and worse as the bearings "Go to hell in a hand basket"??

And how long do you think it would take before I saw a loss in oil pressure?

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Larry Madsen
Las Vegas Nevada



<font size=-1>[ This Message was edited by: monstermach on 1/21/02 12:36am ]</font>
 

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I would think so. More room to move so to speak. How long the bearings last is kind of a coin flip. The worse the vibration gets the more damage it will do in shorter order.

When I built this last engine It had a balance problem after it was together. Come to find out a buddy had swapped flywheels with me while it was in parts. The vibration did the same as yours but in a higher rpm range. I was pissed to pull the clutch and find a 80s flywheel on my 72 block. Same buddy has a 250 6 he races in a falcon. New flywheel from Clifford research. Same thing. He had that motor apart several times before I talked him into having it's balance checked. The virgin crank that you have does worry me though. Since it's never been tested there is no way to know without pulling it. Check every thing else first. Out of balance cranks are rare. 'Specially after a pro balance job.
 

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Discussion Starter #13
The damper I have on the engine is a brand new "factory style" damper (bought specificlly for this build) ... Not say it couldn't be bad, but it is factory fresh so we can be sure it's not old and delapidated atleast.

As for the Flywheel ... it was checked and "re-balanced" when the engine was out and in the shop for the vibration / oil leak problem just a couple of months ago.

I'm convinced there isn't a "large" margin for error on those pieces ...

What I was thinking of doing after I check the "externals" you all have mentioned here ... is taking it to three or four service providers I know and trust ... let them drive the damn thing and look it over and get a "hands on consensis", before I pull the engine out of the car again. If I do it won't go to the same shop for "the fix" ... The shop that did the work on "The Beast" (that's the engine in my Mach1 for anyone not familiar) did an incredible job ... I can hardly believe I had this work done at a different shop


If anyone has more input ... I'm still listening.
 

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You said it was internally balanced. Doesn't that mean that both the damper and the flywheel are neutral balanced? Are you sure that is what the machine shop did? The rear main is still leaking? That doesn't sound good my friend. You should talk to Cobrajack he had a rear main leak in his 351-W stroker motor.
 

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Discussion Starter #15
Yeap ... As I understand it ...

Each individual piece, Damper, Crank and Flywheel should balance to Zero ...

Then of course ... the entire assembly (as a whole) should balance to zero.
 

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Did they use any Mallory (sp) metal (the heavy stuff) when they balanced the crank? If so is it possible that some could have fallen out? I'm just trying to think of every possible scenario. When they balanced the assembly was the clutch and pressure plate attached?
 

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Discussion Starter #17
Yeap ... The shop had all the pieces when original balancing was done.

The Crank Kit came as a complete package (crank, rods, pistons, rings, everything ... At that same time I supplied the damper ... The shop supplied the flywheel from their stock.
 

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Have you removed the fan to see if that would help. I have a buddy with a Chevy big block that had a bad vibration related to RPM and turned out it was the clutch for the fan. Replaced the clutch and problem was solved.


Blue Fastback
 

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Hmmmm...

Internally balanced?

I'm thinking coupe3w hit the nail on the head.

You said you are using a stock type dampner, does it have no counterweights?

Did the shop balance the engine with your dampner and flywheel?
 

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Discussion Starter #20
I could pull the Alt belt and fire it up ...

That will eliminate the Alt and fan and water pump form consideration all in one fell swoop ...

I'll try that after the game
 
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