Engine vibration from 3000 RPM up ?

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427dart
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Engine vibration from 3000 RPM up ?

Post by 427dart » Thu Oct 12, 2017 9:25 pm

A fellow was telling me about a vibration issue he is having with a 351 Windsor he recently bought. It was rebuilt at some point and the parts used
are unknown.
What he told me is the vibration starts around 3000-3500 RPM and continues up thru 5000 RPM and is noticed of course when going thru the gears being installed in a manual trans 89 Mustang.
They checked for engine movement contacting the chassis,header and exhaust contact and other sources with nothing there.
However they did notice the harmonic balancer had a wobble to it and replaced it with correct 28 ounce balance unit.
The vibration was still there and it does it while in Neutral which eliminates other drivetrain issues.
So they tried a 50 once balance flywheel and a Zero balance plus different harmonic balancers which resulted in more vibration and vibration at idle and above. Seems that 28 ounce it what it should be but the vibration is still at higher RPM.

Any clue as to what might be going on other than a complete engine tear down to see what he has? He says the engine runs strong other than the vibration.

Circlotron
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Re: Engine vibration from 3000 RPM up ?

Post by Circlotron » Fri Oct 13, 2017 12:10 am

A friend had a similar vibration problem that (after the engine was pulled down and rebuilt trying to fix the problem!) turned out to be the rubber mount under the trans extension housing. The wrong bolt was used and being too long it reached far enough that there was a metal connection from the trans to the crossmember. Very annoying.

Geoff2
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Re: Engine vibration from 3000 RPM up ?

Post by Geoff2 » Fri Oct 13, 2017 6:00 am

I am not well versed on Ford engines, but the bloke who used to do my engine balancing told me an interesting story. He had a Fairlane, I think it had a 289 engine [ I know it was a s/b Ford ] . He swapped the pistons for 302 pistons, but did not re-balance the engine. He did this as an experiment to see how much vibration, if any, would be caused by this. It had a noticeable vibration at about 3000 rpm.

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Re: Engine vibration from 3000 RPM up ?

Post by cgarb » Fri Oct 13, 2017 7:11 am

What was the difference in a 289 and a 302 piston? Pretty similar pieces, did you know the weight difference? A 289 rod is a little longer than a 302 5.155 vs 5.090. I've heard of people back in the day swapping rods and then cutting some off the pistons to get the deck clearance they want.

Circlotron
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Re: Engine vibration from 3000 RPM up ?

Post by Circlotron » Fri Oct 13, 2017 7:18 am

427dart wrote:
Thu Oct 12, 2017 9:25 pm
The vibration was still there and it does it while in Neutral which eliminates other drivetrain issues.
What about in gear with the clutch disengaged?
If the spigot bush is bad the input shaft and clutch plate may be running off centre.
The above will prevent the clutch plate rotating so if it smooths out or at least changes somewhat it could be this.

DaveMcLain
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Re: Engine vibration from 3000 RPM up ?

Post by DaveMcLain » Fri Oct 13, 2017 8:01 am

cgarb wrote:
Fri Oct 13, 2017 7:11 am
What was the difference in a 289 and a 302 piston? Pretty similar pieces, did you know the weight difference? A 289 rod is a little longer than a 302 5.155 vs 5.090. I've heard of people back in the day swapping rods and then cutting some off the pistons to get the deck clearance they want.
The compression height is the same on both pistons and pistons of the same type will be the same weight. On several 289 engines that I've built I've used the later 5.0 style pistons and the balance required no correction.

Balance factors on the 351w never changed and they are always 28oz even on the later ones with the one piece rear main seal.

Steve.k
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Re: Engine vibration from 3000 RPM up ?

Post by Steve.k » Fri Oct 13, 2017 10:50 am

Did he check engine sitting still? A small dent in driveshaft can cause exactly what your talking about. Rule out drive train.

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Re: Engine vibration from 3000 RPM up ?

Post by PackardV8 » Fri Oct 13, 2017 12:04 pm

Did he check engine sitting still?
The vibration was still there and it does it while in Neutral which eliminates other drivetrain issues.
It's a manual transmission. Was the flywheel and pressure plate balanced with the internals? First, pull the pressure plate and run it up.
Jack Vines
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DaveMcLain
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Re: Engine vibration from 3000 RPM up ?

Post by DaveMcLain » Fri Oct 13, 2017 12:29 pm

PackardV8 wrote:
Fri Oct 13, 2017 12:04 pm
Did he check engine sitting still?
The vibration was still there and it does it while in Neutral which eliminates other drivetrain issues.
It's a manual transmission. Was the flywheel and pressure plate balanced with the internals? First, pull the pressure plate and run it up.
Or was the flywheel resurfaced and they cut a whole bunch more off of one side than the other.. This happens a lot.

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Re: Engine vibration from 3000 RPM up ?

Post by BigBlocksOnTop2 » Fri Oct 13, 2017 2:58 pm

Sounds like an engine teardown to me. Rebuilt with unknown parts, scares me. Your friend probably got it for a song and a dance. Sucks, but I think a balance job is in store after ''knowing what's in the engine''. I had a vibration problem with a ''custom'' drives shaft ( beautiful fabrication and welding) . After taking it someone who knows what they are doing, the problem went away with a rebalance. I know you stated that it vibrates with the trans in neutral. Take the pressure plate off and see if it still shakes. If so, tear the engine down.....

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Re: Engine vibration from 3000 RPM up ?

Post by 427dart » Sat Oct 14, 2017 9:20 am

Thanks for the info. and will pass it along!

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