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Author Topic: Engine vibrations  (Read 422 times)
bryan
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« on: February 10, 2018, 04:23:16 AM »
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Hi everyone, i have a 1959 FC with factory 132 6 cyl and it has this harsh vibration as revs increase. I have replaced engine mounts and harmonic balancer with 2nd hand unit (better condition than original one), have removed front exhaust pipe clamp to engine. I have also disconnected drive belt to eliminate water pump and generator- any suggestions would be appreciated thanks.
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Errol62
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« Reply #1 on: February 10, 2018, 09:02:35 AM »
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It is firing okay? The flywheel isnít loose is it? Thatís relatively easy to check. If that is okay, does the vibration continue with the clutch depressed? If so Iíd say you have eliminated everything external to the short motor. Much piston slap or other noise? Broken piston skirt?


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mcl1959
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« Reply #2 on: February 10, 2018, 09:30:28 AM »
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did you do the front engine mount as well or just the rear mounts.
Ken
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ardiesse
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« Reply #3 on: February 10, 2018, 11:19:36 AM »
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How easily does the engine start?  How smoothly does it idle?  Is the vibration regular or irregular, and does it go with engine speed?

Are there any accompanying noises?

If the vibration's regular, goes with engine speed, and there are accompanying noises, remove all the spark plugs and turn the engine over by hand. (Put the fan belt back on for this.)  With the plugs out, the engine should turn over smoothly, with some but not too much effort.  And the effort should be constant.  If the motor feels like it binds in any position, or if there are clunking sounds as you turn the engine over, that's cause for concern, and needs to be investigated further.

If the vibration is regular, goes with engine speed, but the motor's quiet, put the spark plugs back in and turn the engine over by hand.  You'll be fighting against engine compression this time.  As each cylinder goes into its compression stroke, you should feel quite a bit of resistance, and a muffled "sssh" sound deep in the engine's guts.  This is the sound of compressed air leaking past the piston rings, and is normal.  All six cylinders should put up the same amount of fight, and you should hear the same "ssh"
sound with all six.  You have to turn the motor over at least two revolutions to do this.  If the engine puts up noticeably less resistance on some compression strokes than on others, that indicates bad compressions, and you might even have to get out with a compression tester to confirm it.  Bad compressions mean either head gasket troubles, valve troubles (both of these are a head-off job), or worn or broken rings.

It's a good idea to give the ignition system a quick test.  Start the engine and let it idle.  If the car has its original plug leads, short each plug to ground with a screwdriver: put the shaft of the screwdriver against the rocker cover and slide the screwdriver down until the tip touches the spark plug terminal.  This way you won't get zapped Smiley  If your ignition leads have boots on them, unplug the leads from the plugs, one at a time, and put them back.  Note how the engine note changes as you disable each cylinder in turn.  A healthy engine will go "chuff-chuff-chuff" when you pull a lead.  If your engine is running on five cylinders, the engine note will not change when you pull the ignition lead from the bad cylinder.

In this case, listen to the sound of the spark as you begin to pull the lead off the plug. If the ignition system's good, you'll hear a sharp "tick-tick-tick" sound as you begin to remove the lead.  This is the sound of the spark.

If the spark is bad at any cylinder, you need to investigate your ignition system.
If the spark is good at all cylinders, but the engine runs badly, then you have fuel system troubles, or bad compressions.

If the vibration is irregular, and only really happens when you speed the engine up, it may be something as simple as over-advanced ignition timing.  Disconnect the vacuum advance pipe from the front of the distributor, start the engine and see whether there's any improvement.  If things get better, you need to retard your ignition timing.

Sorry: this post has been both too brief and too long.

Rob
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bryan
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« Reply #4 on: February 10, 2018, 05:17:56 PM »
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Thanks for replies very helpful.Yes Ken i replaced front engine mount.I will check compression and the flywheel.Fuel and ignition are ok.
When engine increases in rpm you can feel the harshness through the car. I will check these items and let you know. Thanks again.
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ardiesse
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« Reply #5 on: February 10, 2018, 06:21:32 PM »
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Bryan,

"harshness through the car"

- When revving engine up, with car stationary?
- Or when driving?  In what gear, and at what speed range?

I'm full of questions this afternoon.

Rob
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bryan
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« Reply #6 on: February 11, 2018, 03:59:24 AM »
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Hi Rob harshness when driving or when stationary out of gear. when driving it does seem to come in at around 70 km/hr but i think this because it is some what disguised due motion.
I will try to get onto those checks soon. Cheers.
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ardiesse
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« Reply #7 on: February 11, 2018, 12:01:04 PM »
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Bryan,

I was going to suggest driveshaft imbalance and/or shot uni. joints, but the vibration also happens when the car's stationary.

Rob
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