Flywheel tolerance

[Ken B]

I recently checked my flywheel face with a dial indicator to measure for any wobble. I measured about .008" I then had the flywheel face resurfaced and now the wobble is about .005" Is this an acceptable wobble in the flywheel face? Or, would this be a cause for excess vibration? I checked the end of the crankshaft and it has about a .0015" wobble in it.

[wrndln]

You can shim the crankshaft/flywheel with shim stock if you want to. I think .005" is close enough not to have vibration problems. In Les Andrew's Mechanics Handbook, it states .005" or less is acceptable. Hope this helps.
Rusty Nelson

[Pete]

It all depends on how close you want it and that depends on how much vibration you can tolerate. Different people and books will tell you different numbers.
It all means nothing if it still annoys you when driving.
On our engines, we will face the flywheel flange so it has zero runout. This includes the OD of the flange, welding if necessary to achieve proper fit at zero runout.
This is done before grinding the crank. Then facing the clutch surface. This is a big factor in a smooth clutch closure. We face the flywheel flange surface and check the flange bore for concentricity, correcting if need be.
There are several other things that can be corrected for a high performance engine such as pitch diameter of the ring gear but not necessary on a street engine.
You need to keep in mind that all this diddling around is not going to eliminate the basic vibration of a model A engine. That is built in and can not be eliminated without re-design of the engine.

[pat in Santa Cruz]

Ford's tolerance was .005 and they are pretty smooth there at moderate RPM. I am happier with them less than that tho'. Did you flip the flywheel 180 degrees and see what you get there? A small burr or a small spec of dirt on the mating surfaces of the crank flange and the flywheel will create a measurable difference at the outside rim.

[Patrick L.]

If the flywheel was resurfaced to correct this, then I think .005" is still quite a bit. Was all the crank end-play eliminated when this measurement was taken ?

[George Miller]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by Ken B

I recently checked my flywheel face with a dial indicator to measure for any wobble. I measured about .008" I then had the flywheel face resurfaced and now the wobble is about .005" Is this an acceptable wobble in the flywheel face? Or, would this be a cause for excess vibration? I checked the end of the crankshaft and it has about a .0015" wobble in it.

The biggest problem is the .0015 The factory speck I think was .0005
.0015 you will have 62 lbs jumping up and down. It will vibrate. I would face the crank flange to get rid of the .005.

For some reason the crank grinders think .0015 is ok. But it is way to much. In the old days cranks were ground as close to .000 as they could get it. I remember scraping in the center on the front of the crank to get it to run true. They were some times messed up from a poor pulley puller.

[Ken B]

The .005" was measured on the outer face of the flywheel where the clutch plate is so the wobble is in and out and not up and down. I haven't tried to rotate the flywheel 180 degrees as it was marked for this position. The face of the crankshaft measured about .0015" I am reluctant to shim the face of the crankshaft. If I shim about .001" around the bolt on the low end then the two adjacent bolts would have a small gap. I have never heard of shimming this area before. Is it a common practice?

[Tom Wesenberg]

Originally Posted by Ken B

The .005" was measured on the outer face of the flywheel where the clutch plate is so the wobble is in and out and not up and down. I haven't tried to rotate the flywheel 180 degrees as it was marked for this position. The face of the crankshaft measured about .0015" I am reluctant to shim the face of the crankshaft. If I shim about .001" around the bolt on the low end then the two adjacent bolts would have a small gap. I have never heard of shimming this area before. Is it a common practice?

One or two layers of aluminum foil in a 120* pie section would probably do the trick for you.

[Chris in CT]

Hi Ken,

You really want to try for 0.0002 perpendicularity of the flywheel flange (on the crankshaft) to the extended centerline of the crankshaft itself. Assuming that the mating segment of the flywheel itself is true (a very large assumption) you will have a little over 0.001 wobble on the outside rim of the flywheel when it is bolted up to the crankshaft. A skillful and saavy crank grinder can do this on the crank when it is being re-ground, or the crank can be chucked up in a lathe with a steady rest and the flange trued with the tool-post grinder. Lots of things have happened with these cars and their flywheels over the last 80 years, and sometimes it can be difficult to figure out just exactly where the problem actually originates.
I had a friend who had measured 0.005 runnout on the O.D. of his flywheel (when attached to the crankshaft) who actually turned the flywheel, mounted to the crankshaft, in his lathe, to true the flywheel to the centerline of the crank. This also included bushing the pilot bearing hole so that it was true, and then re-balancing the flywheel separately. Of course, at this point his flywheel would have to be permanently indexed to his crankshaft... Are we having fun, yet?

----------------------

www.burlingtoncrankshaft.com

[Ken B]

Thanks to everyone for their replies. I will pull the flywheel off and give the shim suggestion a try and inspect the surfaces for any burrs. Unfortunately, this is the last thing I checked before getting the engine back in the chassis. I know now that this should have been one of the first items to check while the engine was apart. I was told that this engine was rebuilt years ago and not run. The rods and mains were all around .001" to .0015" and no end play in the crank. I wanted to take it all apart to go through it for my own piece of mind as we have all heard it in the past "It is all rebuilt"

[Ken B]

Well, I am fortunate to live near and know Joe Thorn from Metalcrafters in Stevens Point, Wisconsin. He said he will be able to set up my engine at his shop and face the and of the crankshaft to take the .0015" wobble out of it. He agrees that it should be as close to .000" as possible at the crank face. I know he does a great job on Model A engine rebuilding.

[Ken B]

Well, I got my engine back from Metalcrafters in Stevens Point. They did a great job of resurfacing the crank face without taking the crankshaft out. I now have only about .001" wobble on the outer edge of the clutch plate surface when the flywheel is back on.

I now have a question about the pressure plate adjustment. I have a new clutch disk and pressure plate. I adjusted the arms to 5/8". I noticed that the adjustment screws and nuts turned very easily. Do these typically hold their adjustment? I did put on some locktite as a little extra peace of mind.

[Tom Wesenberg]

You should stake the nuts into the screw slot to lock them.

[hardtimes]

Hey Pete,
'built in and cannot be eliminated'... What about using a harmonic balancer, of some type, mabe on the crank, would that do anything ..good/bad/nothing? Have you used them?
Mind you, I don't know how such would be attached to the A/B crank , but wouldn't think that that would be impossible?

[Mark in MT]

Hardtimes: It is possible to put a damper on an A crankshaft. I modified a fluid damper for a sbc to fit a B crankshaft. Had to change the front motor mount and the pulley, but as it was in a speedster with an electric waterpump and electric fan, it wasn't a big problem.

[hardtimes]

Originally Posted by Mark in MT

Hardtimes: It is possible to put a damper on an A crankshaft. I modified a fluid damper for a sbc to fit a B crankshaft. Had to change the front motor mount and the pulley, but as it was in a speedster with an electric waterpump and electric fan, it wasn't a big problem.

Mark, Thanks!
Interesting. Did it have the desired affect or any noticable diff? Any pics to share?

[Pete]

Originally Posted by hardtimes

Hey Pete,
'built in and cannot be eliminated'... What about using a harmonic balancer, of some type, mabe on the crank, would that do anything ..good/bad/nothing? Have you used them?
Mind you, I don't know how such would be attached to the A/B crank , but wouldn't think that that would be impossible?

A SBC damper is very easy to adapt to an A or B crank. I have done quite a few..You have to trim the cross member a bit on a stock frame.
It definetly helps reduce harmonic vibration. How do you tell when you can't feel it??? Just feel the damper after driving the car for a half hour or more. It is warm..That tells you it is doing it's job.

[hardtimes]

Thanks Pete for the learnin and the picture! Do you have a web site?

[Pete]

Originally Posted by hardtimes

Thanks Pete for the learnin and the picture! Do you have a web site?

No.