Vibration

[Fred]

I agee, DRIVE TRAIN ?? rear end, cross members, motor mounts ?? U joints !!

[Milton]

"I'd like to understand how an improperly shimmed flywheel housing can cause vibration."

Because the shims go on the top two bolts and prevent the flywheel housing from being pulled out of alignment (bending) when the throttle is installed. If it is out of alignment then the transmission will not line up with the crankshaft. Eventually bearings in hard to get to locations die.

[Milton]

If the engine has modifications to increase power, the scrawny crank will allow rotational vibration. Bad news after a while but, can be remedied with a harmonic damper.

[Smitty]

I know that without the shims it is likely to develop cracks in the flywheel housing.

[30Tudor]

Good Thread. What is the run-out on the flywheel housing supposed to be?

[James Rogers]

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Originally Posted by MikeK

Well, you really lost me on this one. Your original post was about vibration in the ENGINE, not drive-train. Now the subject changes? So, if you knew what you were looking for rather than having any interest in open suggestions, what was the purpose of your initiating this thread? To get on a soapbox and preach about what somebody else didn't do and you do? I get enough of that on Sunday. I'm not impressed.

I am posting about the ENGINE. The vibrations caused by this are evident without moving the car and only the engine running. I stated in the FIRST post I had found some vibrations I had never heard explained by the problems I had found. I am not on a soapbox, I just found this and had never considered it before. Just a heads up for those who care. I certainly was not trying to impress YOU! If you don't like my post or have some personal problem with me, don't read them. As for Sunday, maybe you need to listen a bit closer.

[James Rogers]

Originally Posted by 30Tudor

Good Thread. What is the run-out on the flywheel housing supposed to be?

I believe .003 is the max run-out for the flywheel housing.

[roddyb34]

I am interested to read any information i can on Vibrations ,Fordbarn has informed me so much so far ,,i didnt know about the flywheel housing shimming ,as i am about to embark on an engine rebuild and refitting to the chassis i am keen to read everything ,,,thanks guys,,,

[James Rogers]

Originally Posted by roddyb34

I am interested to read any information i can on Vibrations ,Fordbarn has informed me so much so far ,,i didnt know about the flywheel housing shimming ,as i am about to embark on an engine rebuild and refitting to the chassis i am keen to read everything ,,,thanks guys,,,

Not knowing is only part of the problem. There is no good way to shim the housing in the horizontal plane. This means the housing needs to be checked and re-surfaced to make it flat.

[Rowdy]

James, while your idea has alot of merrit and I agree with it in a running vehicle I am not fully convinced that is the full reason. Case and point: a recently rebuilt engine ran on the stand with no transmission vibrated pretty good. The flywheel housing/ transmission alignement was not in the equation. This engine had been well balanced at the machine shop that built it. Had a well known and trusted person poor the bearings. Alot of attention to the details with this build.

Another engine in my shop put together on a budget has little to no vibration at all. Used crank that was just polished as it was round and was the riht size for the bearings as they were. NORS rods balaced the best I could. Ran on the same stand with no transmission

I have no idea why the one balanced by a pro vibrates, and the one pieced together doesn't. Rod

[Kurt in NJ]

On page 218 of Service bulletins it gives the specs for flywheel housing runout---
"If either the inner or counterbored face of the housing are out more than .006" insert a shim----"

This checking of runout can also be carried out to the trans case bores ---that is where checking of flywheel housing runout is intended to provide a straight line for the transmission shafts, the idea being that the centerline of the trans is the same as the engine.
With all that our cars have been through in the last 80 years perhaps the flywheel housing itself may need to have a non spec alignment to have a true alignment of the trans shafts.

[Richard Lorenz]

For Rowdy: If the balancing of the parts of the rebuilt engine were done separately only, this might explain the vibration. If the regrind of the crankshaft was not exactly on the original centerline, balancing of the flywheel while on the crankshaft would be needed.

[Rowdy]

Richard I discussed those issues with him when he called me before he started on it and I am sure he went the extra mile on it. I also discussed the issue of making sure the cyl bores were back where they are supposed to be. Knowing him for 30 plus years I am sure he checked all of this and did it properly. Engine is pretty snappy, just has the bad vibe. Rod

[BRENT in 10-uh-C]

Originally Posted by Rowdy

James, while your idea has alot of merrit and I agree with it in a running vehicle I am not fully convinced that is the full reason. Case and point: a recently rebuilt engine ran on the stand with no transmission vibrated pretty good. The flywheel housing/ transmission alignement was not in the equation. This engine had been well balanced at the machine shop that built it. Had a well known and trusted person poor the bearings. Alot of attention to the details with this build.

Another engine in my shop put together on a budget has little to no vibration at all. Used crank that was just polished as it was round and was the riht size for the bearings as they were. NORS rods balaced the best I could. Ran on the same stand with no transmission

I have no idea why the one balanced by a pro vibrates, and the one pieced together doesn't. Rod

Rod, what James is saying does have some merit IMHO but what are you thinking is the cause? James & I are finding that it is not uncommon to find flywheel housings that are .10+ out horizontally, --which means the shims really don't do a lot for correcting that issue.

Now two theories I have with this;
I know some people here are proponents of the Float-a-Motor mounting system but when you think about a Model A design, the rear wheels/tires are pushing the driveline forward to move the vehicle. The place that everything ties together is the rear engine blocks that attach the flywheel housing to the frame. When one of those blocks (mounts) becomes damaged/cracked, it only leaves one block to push the vehicle by. I am of the opinion that over time, the constant pushing/pulling force will "tweak" the flywheel housing enough for it to become out of specs. That is why I think the housing needs to be indexed off of the Clutch Housing (bell housing) mating surface and then flycut to ensure both surfaces are parallel.

With regard to your 'pro-built' vibration scenario, I think it is entirely possible the flywheel housing could still be warped and when you indicated the flywheel in while on the stand, it gave you a false reading. If you did not indicate the flywheel, I would start by using an indicator on the crank flange and see what you have. Then measure the flywheel using the back of the block as the base for your indicator. Once the flywheel is within specs, mount a bracket on the flywheel and indicate the Clutch Housing mating surface and see what it is. I'd bet something is not gonna be to your liking.


.

[Rowdy]

Since the engine is now in the car it is not likely the owner is going to pull it out to let me check, but it would not suprise me to see something. There was a slight issue with the cam timing gear when it was first installed, but that was corrected. I have an idea as to what the main cause is, but without some engine failure for me to investigate I will not get that chance. This is the same owner that has many body alignment issues with his coupe, but refuses to let me pull the body back off and fix the real problem which is the frame. Guesse he is one of those that is just content to say it is together, so it must be done. Rod

[MurphyJ]

Thanks James Rogers for posting this thread as I have been searching for a vibration in my "A" now for over a year. Any clues, suggestions, ideas or others are greatly appreciated as Ford Barn members have a vast amount of knowledge and experience.

[Louis]

Originally Posted by James Rogers

Good one and probably attributes to lots of engine vibrations. More?

.

Im kinda new to the model A, I also have a eng. vib. that I think is to much.
I looked under the car to look at the frt. eng. mount to see if it was to loose, But the frt. eng. mount looks nothing like the one on page 1-151 in Les Andrews hand book, instead of a spring this one has a large rubber cushion, Is this Pic. the correct frt. motor mount?
Should i leave it alone, or get one like the hand book shows ?
Thanks for any advice.

[marc hildebrant]

Interesting note.

I have vibration that starts around 40 MPH. One version is that they "all do it".

However, in the past I taked to a Model A owner of an original motor setup, who claimed that he would cruise at 55 mph with no vibration !

Sure would like to know if I should work on the vibration or not.

Marc

[Louis]

Marc,
My 31 coupe runs smooth at 35 and the vibration starts about 37-38 but then smooths out around 40-42. Seems like it run's better in a slight up hill then a slight down hill. Mine was rebuilt in 1972 and sat untill i bought it last year. But i don't have another A model to compair it to. I keep hearing about some that say they can drive there stock A model about 50-55 mph, I don't know .

[Barry B./ Ma.]

They seem to like it at 42-45 and beyond that get buzzy. My coupe has an overdrive and the comfort range goes up to 50-55. No two A's are the same so keep that in mind (one of mine is smoother than the other).