Vibration

[James Rogers]

Just thought I would start a thread to get opinions from barners about what might be the source of vibrations in a Model A engine. I have never run a totally original motor so, I don't have any experience as to that type of smoothness but, I have run several that were real shakers and one that was as smooth as a modern V8. I have some opinions of my own and will express those as this post progresses and others give theirs. I have found some places that I believe will cause vibrations that I have never been warned of expressly. Hope to hear lots of opinions so I can get verification of my findings and maybe help others calm their engines down some.

[Jim Huseby]

This will be interesting when all answers are in. I'll just name one: front motor mount center stud nut wound down tight.

[James Rogers]

Originally Posted by Jim Huseby

This will be interesting when all answers are in. I'll just name one: front motor mount center stud nut wound down tight.

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

[Brentwood Bob]

wrong plunger spring in timing gear cover. Same dameter, but short, so very weak pressure on the cam. Bob

[Gerard]

A totally wrong grounded camshaft combined with a wrong dialled position of the camshaft gear. ( to just name a few )

[newshirt]

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Wobbly fan blade.

[BRENT in 10-uh-C]

...in addition to ones mentioned above;

Worn Distributor Cam

Unbalanced Flywheel

Unshimmed/Improperly shimmed Flywheel Housing

Bent Connecting Rod

Crank Pulley

Improperly ground Crankshaft

Reciprocating assy not balanced after rebuild (i.e.: thick babbitt on rod)

.

[Mike V. Florida]

how about the pictures we saw of different connecting rods? I would think there are engines that have mismatched pistons and connecting rods.

Low compression in one cylinder.

[pat in Santa Cruz]

bent crankshaft, crank ground off center, rod pins not indexed when crank ground, unbalanced fan, unbalanced pistons and/or rods, uneven compression due to combustion chambers not having equal volumes, cylinders bored off center, main bearings not align bored correctly, flywheel not seated properly on crank shaft. Also, often mis diagnosed as engine: bad U joint, bent drive shaft,

[Fred]

1928 style front motor mount bolts loose/missing..

[ford1]

the biggest reason is the crank shaft is not counter balanced, you will hear guys say that is not the reason, i say if not why did ford start counter balancing them in 32?

[Keith True]

I have an early 31 Tudor that vibrates some from about 30-40 MPH.It really should vibrate a lot more.When I got it,I got it running after a 25+year sit.The head gasket blew within a week.It was a steel clad gasket,simply rotted.What I found was a surprise though.No two pistons protrude from the top of the block the same amount.The car shouldn't run that smooth.The windshield setting material had dried up,and between 30-40 MPH the windshield buzzes in the frame.In high school I worked for a man that patched up A's for people that used them to run to work in the mills.Most lived within a mile or two of the mills,and some owned those cars for 30+years.That guy did things to an A that he would never do for somebody that actually wanted an A for a driver.If you scored a cylinder wall,he would bore one,and put in a used oversize piston for you.He showed me one car that had four different size pistons in it.He only did this for people that drove 2-5 miles a day,and 30 MPH was as fast as they ever would get up to.Some of those would start to vibrate at 30 and just get worse from there.Mill pay ranged from $1.80-$2.25 per hour,so doing it 'right' wasn't in the cards.I remember somebody showing up with a JC Whitney rebuilt for him to install.He said we'd better look in it first.The owner said,why?it's a rebuilt.Two different sized pistons,different protrusions above the block,two regular connecting rods and two X rods(I still have them),three rod journals at .020 and one at .040.And,every time you turned the crank around,it would bind up on the cam gear in one spot so tight you could see the cam gear trying to bend upward.

[George Miller]

Originally Posted by James Rogers

Just thought I would start a thread to get opinions from barners about what might be the source of vibrations in a Model A engine. I have never run a totally original motor so, I don't have any experience as to that type of smoothness but, I have run several that were real shakers and one that was as smooth as a modern V8. I have some opinions of my own and will express those as this post progresses and others give theirs. I have found some places that I believe will cause vibrations that I have never been warned of expressly. Hope to hear lots of opinions so I can get verification of my findings and maybe help others calm their engines down some.

One thing I found on my 28 engine is that the cylinders were bored off location. They are not in the right location. Some one must of located from the worn spots in the cylinders. They were so far off the piston rubbed the rod at the wrist pin. Not sure that would make it vibrate, but not good.

[MikeK]

Volume inequality between combustion chambers. As-cast chambers can vary 10cc or more.

[James Rogers]

Well, this is not really going where I figured it would. I figured someone would mention the flywheel housing which, I think, is the source of most vibrations in the Model A drive-train. Many don't check it or don't know it needs adjusting because I find so many motors that don't have any shims under the throttle assembly mounts. I checked one last week and found the run out was in an unusual place. The flange was out .005 and the flywheel was out .003 at the outer diameter but, the housing was out .020. The unusual part was it was out at the motor mounts. There is no adjustment for this run out and most would not expect cast iron to flex and warp that much but, this did. I figure it was because of being run for years without shims in the top mounts and the frame bent. I don't know about this but it sounds as good as any explanation. I had the housing resurfaced and it was warped .016 from one mount to the other. This would throw the engine to transmission out of line a couple of inches from crank pulley to the universal joint. This, IMHO, would be a cause of vibration if all other sources are in spec. Might pay to check this on the next removal.

[Smitty]

So what then is normal vibration? I have 3:54 gears in my rear end and I am finding that from about 45mph and above I get some vibration. Also if you let off the gas at 45 and above the car is loud and slows quickly as if it were in a low gear.

Steve

[James Rogers]

Originally Posted by Smitty

So what then is normal vibration? I have 3:54 gears in my rear end and I am finding that from about 45mph and above I get some vibration. Also if you let off the gas at 45 and above the car is loud and slows quickly as if it were in a low gear.

Steve

I don't know what would be normal, I guess it depends on the person. I drove a Phaeton at Brent's shop that was the smoothest motor I have ever started. This motor is as smooth as a modern small block.

[Smitty]

My coupe has plenty of power and I am considering an overdrive only to reduce vibration and quiet the car. A smooth motor would be nice alternative if such a thing is possible.

[MikeK]

Originally Posted by James Rogers

Well, this is not really going where I figured it would. I figured someone would mention the flywheel housing which, I think, is the source of most vibrations in the Model A drive-train. Many don't check it or don't know it needs adjusting because I find so many motors that don't have any shims under the throttle assembly mounts. . .

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.

[newshirt]

Originally Posted by James Rogers

Well, this is not really going where I figured it would. I figured someone would mention the flywheel housing which, I think, is the source of most vibrations in the Model A drive-train.

Flywheel housing was mentioned in Post #7. (Brent)

I'm new to this, so I'd like to understand how an improperly shimmed flywheel housing can cause vibration. I believe it can, but don't understand why. Can anyone explain it?