Engine Vibration

[Pete]

Originally Posted by ursus

So, are you saying that the crankshaft should be balanced separately from the flywheel/pressure plate assembly?

Here we go again.
THERE IS ONLY ONE PROPER WAY TO BALANCE CRANK ASSEMBLIES.
If it is an inline 4 cylinder, you balance the rods and pistons first. Plus or minus 1/2 gram on that stuff.
Then you balance the crank both statically and dynamically with no front pulley, damper or flywheel.
Then you put whatever goes on the front of the crank and balance that statically, making any adjustment on that attachment. Then you attach the flywheel and balance that statically, making any adjustment on that only. Then you attach the clutch cover and balance that statically, making any adjustment by drilling the spring towers. Never weld on a clutch cover.
Then, recheck the whole assembly for dynamic balance.
All of this assumes the rebuilder checked the runout of the crank, front pulley and flywheel/clutch assemblies at assembly time.
The clutch disc can be balanced on a separate arbor.

All model A/B engines have natural resonant frequencies/rpm's that they vibrate at. These are minor and you can not get rid of them without redesigning the engine. They had these right from the factory.

[maxamillan]

Where did you get a harmonic balancer pulley from?

[wensum]

These dampers are made by Murray Horn in Levin N.Z. His Company is Engine Restorations Ltd. His email is [email protected]
Murray says this is the best way to contact him.
The dampers are a straight fit to replace the standard Model A pulley. An added benefit is a shallow reverse scroll in the rope seal area to help contain oil.

[imacrazy]

Wensum, could you tell me where you got your harmonic balancer pulley ?


Thanks, Bill

[daren007]

Why would you balance the rods and pistons first?

[Kohnke Rebabbitting]

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Originally Posted by daren007

Why would you balance the rods and pistons first?

Because that is the easiest thing to start with, and the most times that they are out !


Also, Bad Rod alignment will make a mess of good Balance!



Herm.

[Pete]

Originally Posted by daren007

Why would you balance the rods and pistons first?

It is not essential for an inline 4 cylinder, but, when you balance a V8 you need to do them first because you need to record the weights to make up the required bob weights. No bob weights are required for an inline 4 cylinder street engine.
So it comes down to using the same sequence of events for all engines. Less procedures to remember and get confused.

[Lawrie]

Peter, when you say to balance the parts statically,how do you do that,
I,m very interested.
I have the scales and fixtures to do the rod and pistons and stuff but not the crankshaft
I could save a lot of $$ at the reconditioners If I can get the static close first.
Lawrie

[Pete]

Originally Posted by Lawrie

Peter, when you say to balance the parts statically,how do you do that,
I,m very interested.
I have the scales and fixtures to do the rod and pistons and stuff but not the crankshaft
I could save a lot of $$ at the reconditioners If I can get the static close first.
Lawrie

It is possible to rough balance a 4 cylinder inline crank statically on rollers or knife edges.
The heavy side will always seek "down".
Static balance is balance in one plane. Dynamic balance is balance in overall length. It is possible for a crank to be in balance on one end but not on the other end or in the middle. A balancing machine is required to detect this.
You will not save much if anything by knife edge balancing before you have it balanced on a machine.

[wensum]

Originally Posted by imacrazy

Wensum, could you tell me where you got your harmonic balancer pulley ?


Thanks, Bill

See my response above
Cheers
Keith

[Richard Lorenz]

Thanks again for everyone's suggestion. We checked camshaft timing by watching piston #1 top out. It agreed with the NUREX timing scale and our old mark on the pulley when the timing pin dropped into the detent on the fibre timing gear.

We also checked the compression with the engine warm , probably about 160 F. Results front to back were 58, 63, 62, 60, and 58 psi. These are slightly higher than previous room-temperature measurements, but nowhere near the 100 psi that could be expected with our 5.5 Snyder's head.

As soon as it quits raining in East Tennessee, we will put some driving time on the car to finish the break-in. Richard Lorenz

[Tom Bellfoy]

Richard:
I had the exact problem you have, my professionally rebuilt engine vibration was between 0 and 30 MPH, noisy above 30 MPH. I was ready to give up from frustration as I refused to drive it anymore. I believe my problem started after I installed my rebuilt engine and tightened the stock front mount too tight and thus not lining up the crank hole properly. I then decided to install both front and rear float-a-motor mounts which didnt help much. I removed the front float-a-motor and reinstalled the stock front mount, kept only the rear float-a-motor mounts making sure the rubber was not too tight.

The problem went away completely, no vibration at all and very quiet - no harmonics sound. Make sure the front stock mount is lined up properly with the crank hole.

let me know if that makes a difference for yours
Tom