So, really, in a well tuned Model A, how much vibration is 'normal'?

[DougVieyra]

I set a dime on edge at the top of the front left fender. With engine running and transmission in neutral, If the dime remains 'standing' during all phases of the quadrants, I am happy with the vibration level of my Model A.

[colin1928]

Another area that needs to be addressed is the flywheel housing alignment
I have seen a miss aligned/cracked/broken flywheel housing cause the same amount of vibration as talked about in the OP

[P.S.]

Follow-up:

SO, I knew the motor was rebuilt properly (a "touring motor" from a very popular Model A motor shop that has a reputation for very good work), the problem had to be me. It was.

When I had the motor rebuilt, I requested the "touring motor" package and got it. Toward the end of the time he had the motor, he called and asked me to bring the clutch pressure plate over so he could have it balanced along with the flywheel. I was away on business and could not get it to him in the timeframe he requested. Since the pressure plate came off my other motor and was "balanced", I didn't think it would be a big deal. The rebuilder had the motor running on a stand when I picked it up, and it was smooth. I took it home, installed it, and it ran STRONG, but vibrated as mentioned in the OP. Not teeth-shaking vibration, but enough to make the rear view mirrors 'blurry' at certain RPMs. I just assumed that was normal.

OK, now fast forward.

I got another flywheel from a friend (adopted dad) that was stock weight. I took it and another original pressure plate to a machine shop and had them balanced. He first balanced the flywheel alone, then he mounted the pressure plate to it and balanced it. He marked where they mated on the balancing machine, so I could reassemble the same way. Last weekend, I swapped the flywheel and pressure plate in the tudor.

Using suggestions from fellow barners, I removed the rear end and tranny so I could run the motor with the flywheel and P-P combinations as an experiment. With the old flywheel and P-P, the motor vibrated. Removed the P-P and clutch disk, ran it again. Less vibration. Swapped the flywheel to the new full weight flywheel. MUCH smoother and quieter. Installed new P-P and clutch disk- Still smooth and quieter. Verified they were running true, reassembled the car and drove it.

First impression - It is MUCH smoother and quieter! Not quite as smooth and quiet as the 99.9% original fordor, but pretty close. Keep in mind, I am now running a counterbalanced crank AND a full weight flywheel (I'm sure I will get flamed for this). It will idle down to 200 RPM, and keep running. Sound level inside the car while driving at highway speed is about half of what it was before.

Gear shifting- No difference. Shifts exactly the same as before.

Hill climbing - This is where I notice a major difference. Going home, there is one road that is a steep climb for a little over 1/2 mile, and almost all straight. With the previous flywheel in place, I could make it maybe 1/3 of the way up that road, then would have to downshift to 2nd for the rest of the climb. Having changed nothing else except the flywheel and P-P, I can now take the whole hill in 3rd gear, no sweat. It is as if I added 10 HP that is only noticeable when climbing hills. On the flat and level or on a downhill, there is no difference from the lightened flywheel. Only notice this when climbing steep hills.

Even on the gentle rolling hills on the highway below, you sorta notice it there too. I don't have to give it as much gas to make the hills now. Yes, when revving the motor, it takes a fraction longer to spool up. It is barely noticeable though.

I am no motor builder and no machinist, I'm an electrical engineer. So, I am not prepared to argue the engineering for a lightened flywheel. However, as a Model A owner, I am convinced that the flywheel weight Henry Ford chose is much better than the lighter flywheels popular now.

[mshmodela]

P.S.

Thanks for the detailed report... as a former EE myself (do programming etc. now) I recall that one can make "moment of inertia" of a flywheel greater with more mass from the center --or by removing mass from the center.. e.g. pulleys that that are not solid, e.g.



I would guess a lightened flywheel is similar to some degree --maybe.

[Mitch//pa]

Paul I am glad the ideas seemed to work out and your vibration is basically resolved

[Barry B./ Ma.]

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They are all different, I've had smooth ones and have had rough ones. Probably matched weights and assembly are different also some have balanced crankshafts. My present coupe is smooth right up to top speed and doesn't have a balanced crank.
P.S.
When I originally bought the coupe back in the early eighties the original engine vibrated so much the rear inside mirror shook. That engine ended up in another car and it vibrated there too, had it rebuilt and it still vibrated.

[RonC]

Originally Posted by P.S.

I have an unrestored Fordor that used to have the original motor in it, no balanced crank or anything, and it was pretty smooth. Got the motor rebuilt and it vibrates a bit more than it used to.

Also have a restored (fine point level) Tudor with a rebuilt motor that has all the fancy doo-dads like insert bearings, balanced crank, lightened flywheel, etc. and it vibrates the steering wheel right out of your fingers at certain RPMs! The body doesn't vibrate much, but you can sure feel it in the steerng wheel (all vibration is from the motor, not steering or road vibration)

So... How much Model A vibration is 'normal'? Is there any reason why the fully balanced motor should not be smoother than the unbalanced motor?

I'm not talking about Model As in bad shape, I'm talking about the Model As you guys poured your full effort into that you can reliably drive anywhere, anytime.

P.S before you blame the engine one source of vibration is misalignment of the drivetrain. From the factory Ford set the engines so that you could draw a straight line from the crank pully to the back transmission spline centers. There are two adjustments. One where the flywheel cover attaches to the engine and one at the front motor mount. See the service bulletins for the adjustments. Who is installing your engines?

[P.S.]

Originally Posted by RonC

P.S before you blame the engine one source of vibration is misalignment of the drivetrain. From the factory Ford set the engines so that you could draw a straight line from the crank pully to the back transmission spline centers. There are two adjustments. One where the flywheel cover attaches to the engine and one at the front motor mount. See the service bulletins for the adjustments. Who is installing your engines?

Thank you for bringing this up. I am aware of the drivetrain alignment issues. To answer your question- I installed my own motor each time.

As mentioned in my post from yesterday, the vibration could be felt any time the motor was running, even with the entire drivetrain removed from the car and the flywheel exposed.

Thank you to Mitch, Marco, Brent, and many others for helping in this thread, by PM, email, etc. I learned a LOT!