Vibration in an A

James Rogers

James Rogers

Well-known member
I spent most of today and yesterday in the shop chasing vibrations in an A motor. Not just any motor but a fresh motor going to a customer in St. Augustene. Not that his motor has anything wrong with it but I see lots of people on here complain about vibration at 45 mph or so or their motor just vibrates and the source is so elusive it escapes the owner.

I tried several flywheels on this motor and got several different amounts of vibration. All flywheels were cleaned in a caustic tank so no clumps were present to make them vibrate. I found that, all stock flywheels would cause vibration. All vibrated at different speeds so, I checked them individually on a crank grinder balancer. All were from 1 oz to several oz. heavy in different places. I installed a lightened flywheel and ran the engine and found it ran beautifully and smooth throughout the power band. This is just another reason to install a lightened flywheel and V8 pressure plate. Even if you use the stock flywheel, it would pay to have it balanced on a dynamic balancer to get it closer to correct.
 
Off topic, but my brother and his wife just moved to St Augustine (The Shores) and I will be driving down to visit in a few weeks.
Paul
 
Here is the procedure used by my balancer. He balances racing engines which turn several thousand rpm so I have confidence in his ability. He balances the crankshaft first then bolts the lightened flywheel on the crankshaft then balances the flywheel then he bolts the pressure plate on the flywheel and balances the pressure plate. Using this system each one is balanced individually and can be replaced without screwing up the balance of the system. This system has worked very well for the sixty plus engines I have had my hands on. Just my thoughts.
 
Arlyn Bieber said:
Here is the procedure used by my balancer. He balances racing engines which turn several thousand rpm so I have confidence in his ability. He balances the crankshaft first then bolts the lightened flywheel on the crankshaft then balances the flywheel then he bolts the pressure plate on the flywheel and balances the pressure plate. Using this system each one is balanced individually and can be replaced without screwing up the balance of the system. This system has worked very well for the sixty plus engines I have had my hands on. Just my thoughts.
Click to expand...
So, if you loose a pressure plate or have to replace a component, you have to go through the whole rotating assembly again. I do each piece seperately as modern components are done. That way if one piece goes out I can replace that piece without re-balancing the whole system. You could just replace a broken or worn out part also but, that would defeat the whole purpose of balancing that way. Besides, this is a 3000 rpm engine not a 10,000 rpm racing engine.
 
http://www.fordbarn.com/forum/album.php?albumid=3019&pictureid=25122
Quote:The original flywheel was well balanced when it left Ford, so how do you figure it went out of balance?

Two examples are resurfacing and replacing the ring gear.

As shown in the picture we always rebalance the flywheel and pressure plate as a unit.
Our balancer is capable of balancing to .1 tenth of gram so the closer to zero the better the engine runs and lasts.
Many customers can attest to the difference of a well balanced Model A.
http://www.jandm-machine.com/balancing.html
 
J and M Machine said:
http://www.fordbarn.com/forum/album.php?albumid=3019&pictureid=25122
Quote:The original flywheel was well balanced when it left Ford, so how do you figure it went out of balance?

Two examples are resurfacing and replacing the ring gear.

As shown in the picture we always rebalance the flywheel and pressure plate as a unit.
Our balancer is capable of balancing to .1 tenth of gram so the closer to zero the better the engine runs and lasts.
Many customers can attest to the difference of a well balanced Model A.
http://www.jandm-machine.com/balancing.html
Click to expand...

I often hear the flywheel is balanced to a certaiin gram weight, but at what distance is this?:confused: Thanks
 
forever4 said:
The original flywheel was well balanced when it left Ford, so how do you figure it went out of balance?
Click to expand...
Good question. All I have checked or had balanced except 1 have been out of balance and were totally unmodified or drilled after leaving the factory.
 
A good balancer can move the speed which the vibration comes in. On an A he should be able to move it to a range that you wouldn't use. Say over 5,000 RPM.
 
I have also found, as J&M said, the face of the flywheel is almost always ground out of alignment with the crank center. To grind the flywheel, you must use a ground true center that fits inside the recess for the crank to grind the flywheel face. Most I find have just been placed on the turntable flat and clamped by the center hole and ground. This causes the face to be ground by a surface that is not true to the crank and is, in my opinion, what causes many cases of chatter and vibration.
 
James Rogers said:
So, if you loose a pressure plate or have to replace a component, you have to go through the whole rotating assembly again. I do each piece seperately as modern components are done. That way if one piece goes out I can replace that piece without re-balancing the whole system. You could just replace a broken or worn out part also but, that would defeat the whole purpose of balancing that way. Besides, this is a 3000 rpm engine not a 10,000 rpm racing engine.
Click to expand...

James, Do you balance the pressure plate by it's self?
What about if the crank isn't ground true to center and the true flywheel then has the wobbles?
 
harleytoprock said:
James, Do you balance the pressure plate by it's self?
What about if the crank isn't ground true to center and the true flywheel then has the wobbles?
Click to expand...
I have all my reground cranks checked before using so, the flywheel works great on my stuff. If I sell a flywheel to someone who's crank is ground out of center well,,,, I can't fix that. :(
And, yes on the pressure plate.
 
I get confused very quickly.

James, I understand you lighten flywheels 11#

You mentioned Ron Miller. I believe he lightens his 7#

Dan Price's flywheels have been lightened 38#

Bill Stipe makes a 24# aluminum flywheel which is 41# lighter than original

Whats best ?
 
I believe Ron is using the weight difference of the pressure plate. When the flywheel is modified for the V8 plate, you HAVE to remove 11# minimum by removing the raised ring. The V8 pressure plate is approximately 7# lighter than the stock A plate. The best flywheel is the one that suits your purpose best. For everyday driving and stock idling, mine or Ron's is great and I have sold lots for just that purpose. For racing Dan's or Bill's are good and, I have done flywheels that were for racing that were as light as 25#. You have to decide what is best for your particular application and budget.
 
Just for some general info, a completely stock model A engine can be made to idle at 450 rpm WITH NO FLYWHEEL.
The engine was started with a big drill motor plugged into the crank nose.

I have built several street type model A/B engines using a
12 lb aluminum 350 Chevrolet flywheel and an aluminum 9 inch Long pressure plate.
The reason for the Chev unit? CHEAP, PLENTIFUL and easily modified to fit compared to made for brand units.
The reason most people do this? Better drivability.
A big side benefit, longer engine life due to lower torsional vibration in the crank assembly.
 
FWIW,

At one time it was told to me from a reliable source that more than one NOS flywheel was checked and found to be out of balance. All the flywheels were known to be post A era Ford production.

So a NOS flywheel in a later 30's or 40's box may not be properly balanced.
 
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