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Old 08-25-2017, 10:38 AM   #1
tubman
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Default 8BA clutch finger adjustment

I posted this on the H.A.M.B. because it's about a hot rod. The only responses I have gotten referred me back here.

"I am getting ready to put the clutch and flywheel on the 258" 8BA flathead I built for my "T" tub. I mocked the setup on my bench today ("blocked" the pressure plate and then bolted the pressure plate, disc and flywheel together using the clutch alignment tool and removed the blocks). I then carefully measured the distance from each pressure plate "finger" to the hub of the disc. The three fingers measured 1.225", 1.180", and 1.175" from the clutch disc hub to the contact surface of the fingers. I measured 3 times. All three measurements on each finger were very close and the figures I have presented here are the averages of these measurements. While I would think a difference of .005 would probably be OK, but I don't think the .050 between the highest and lowest to be acceptable.

First question : am I correct in assuming that these measurements are out of the ordinary? Second, if they are (and I guess, even if they aren't), how would I go about correcting them? There are no adjusting screws on the ends of the fingers as I have seen on some other units. Do I grind .050 off of the offending clutch finger? There are three bolts that hold the fingers to the clutch assembly; When I loosen them, the end of the finger drops, but I obviously don't want to run loose bolts in my clutch. I would think that a .004 thicker washer (or shim) would bring the offending finger (did I say that?) down the proper amount.

Should I be worrying about this or not?"

Last edited by tubman; 08-26-2017 at 06:10 AM. Reason: Spelling
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Old 08-25-2017, 10:43 AM   #2
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Default Re: 8BA clutch finger adjsutement

I would measure the clearance between the release bearing and the fingers.
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Old 08-25-2017, 10:57 AM   #3
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Default Re: 8BA clutch finger adjsutement

Like cm posted I would want to see what the measurements were from something like the transmission mounting surface. If you had a bellhousing that mounted to the engine I would measure from the transmission mounting surface of the bellhousing. Guess you could build a bridge across the bellhousing mounting points on the engine and measure from it to the pressure plate.
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Old 08-25-2017, 12:10 PM   #4
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Default Re: 8BA clutch finger adjsutement

I would see if you have runout on flywheel,then mount the presure plate (with out the disk),use 1/4" blocks 3 or 4 then measure. They tryed to copy the orginal fingers but was easier to slice them like bread. If you think you can get them all the same go for it.
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Old 08-25-2017, 12:27 PM   #5
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Default Re: 8BA clutch finger adjsutement

The Ford instructions I have seen measure from a flat bar across the top of the cover down to the fingers. I do not remember the tolerance, but yours seems way high.

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Old 08-25-2017, 01:22 PM   #6
Bruce Lancaster
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Default Re: 8BA clutch finger adjsutement

The Ford adjustment instructions are in the '46 V8 engine overhaul book (the more common later editions lack that section) and in the transmission/overdrive/clutch book which is readily available in reprint. You can get it from Van Pelt sales...while there you should also buy Van Pelt's own transmission book, which is better than the Ford one but without clutch info.
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Old 08-25-2017, 05:18 PM   #7
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Default Re: 8BA clutch finger adjsutement

Read on https://www.google.ca/search?q=adjus...h=726&dpr=1.25

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Old 08-26-2017, 06:12 AM   #8
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Default Re: 8BA clutch finger adjsutement

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Originally Posted by cmbrucew View Post
I would measure the clearance between the release bearing and the fingers.
Bruce
I would think that the relationship of the clutch finger to the flywheel surface would be more important than to the release bearing. All of the component parts (block, bell housing, transmission, and flywheel) have been in service with no problems for over 60 years with no problems. The only new components are the pressure plate and the disc. I would think the problem lies there. This is a new clutch assembly of unknown origin I picked up with a bunch of parts I got from a guy who was getting out of flatheads.

One more thing : Before measuring the bolted together assembly, I laid the pressure plate on the flywheel without the disc and measured the distance from the contact point on the finger to the pressure plate itself. The variation in heights was similar to the variations I got on the assembled unit.

There's all kinds of information on the internet about how to adjust tractor clutches and Model A's (where the adjusting mechanism is self-evident). I could find nothing about this kind of clutch.

Last edited by tubman; 08-26-2017 at 06:26 AM. Reason: Add more information.
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Old 08-26-2017, 06:32 AM   #9
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Default Re: 8BA clutch finger adjsutement

Quote:
Originally Posted by Bruce Lancaster View Post
The Ford adjustment instructions are in the '46 V8 engine overhaul book (the more common later editions lack that section) and in the transmission/overdrive/clutch book which is readily available in reprint. You can get it from Van Pelt sales...while there you should also buy Van Pelt's own transmission book, which is better than the Ford one but without clutch info.
This is good news. However, I was planning on assembling this engine over the weekend, so my chances of obtaining this manual are non-existent. If someone could summarize it here, I would greatly appreciate it. Basically, do I grind the fingers or disassemble the clutch and shim the pivots? If the technique is the latter, I would disassemble the pressure plate and could probably figure out what has to be done. I do not, however, want to disassemble a brand new pressure plate if it is not necessary.
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Old 08-26-2017, 06:33 AM   #10
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Default Re: 8BA clutch finger adjustment

The hub is not a machined surface. Usually these things are set at the factory. I question whether .050 would make that much of a difference. Try loosening the clutch and reorienting it and see if you get the same measurements.
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Old 08-26-2017, 06:37 AM   #11
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Default Re: 8BA clutch finger adjustment

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Originally Posted by Frank Miller View Post
The hub is not a machined surface. Usually these things are set at the factory. I question whether .050 would make that much of a difference. Try loosening the clutch and reorienting it and see if you get the same measurements.
I have tried the clutch in all 3 positions and got similar results. What you say about the .050 difference possibly being inconsequential is good to hear. However, if there is a way to adjust it out, I'd like to do it. As I said in a previous post, I also measured from the flywheel (which is a machined surface and got similar results.
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Old 08-26-2017, 07:41 AM   #12
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Default Re: 8BA clutch finger adjustment

The Ford spec requires the use of a flat plate, not a clutch disc, be in place between the PP and flywheel in order to properly adjust the fingers. Obviously the marcel can affect the flatness and influence finger heights.
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Old 08-26-2017, 10:18 AM   #13
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Default Re: 8BA clutch finger adjustment

Thanks for the information on the flat plate; I think I can come up with something that approximates the thickness of the clutch disc. Now, if someone has a copy of the manual Bruce mentioned, could you look and see what the procedure is? I don't need a detailed description (though that would be nice); just "grind", "shim", or "something else" would be a good start.
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Old 08-26-2017, 01:54 PM   #14
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Default Re: 8BA clutch finger adjustment

I would think that the marcel is not a factor in finger height variation, all it is is a spring steel wave washer and when the spring pressure clamps the disc it flattens it out.
Shimming the yoke of the high lever will lower that finger to the level of the others and since you have two that only vary .005 your fix is relatively easy. Loosen the bolt on the clutch cover that holds the yoke and slip in a shim. The question is how much shim is needed because of the lever ratio, but trial and error will help there. I would use a shim with a forked shape to help keep it in place when tightened.
The alternative is to disassemble the PP and mill the two yokes that have the low levers, but I doubt you want to open that can of worms.
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Old 08-26-2017, 02:12 PM   #15
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Default Re: 8BA clutch finger adjustment

Thank you very much "Fordors". I thought that was how it was done, but didn't want to start fooling around with pressure plate until I was sure. Off to my shop I go!
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Old 08-26-2017, 08:15 PM   #16
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Default Re: 8BA clutch finger adjustment

I just got back from my shop, and after "Fordor"s advice, I was able to figure out how to adjust the fingers. It is actually very easy. I removed the 5/16"- 1/2" bolt from the pressure plate, and was able to position a .015 spacer over the face of the threaded part inside the clutch. I used a small gauge wire to bring it up over the proper position, and re-inserted the bolt. Everything worked out, but now the finger was .050 low. This is because of the ratio on the clutch fingers. I now think that a .007 shim will put me right in the ballpark. Here is a picture of the .015 shim (which was too thick) and the wire that allowed me to insert it. I am going to find some .007 shims that will bring it into spec.
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File Type: jpg 0826171615.jpg (65.9 KB, 72 views)

Last edited by tubman; 08-27-2017 at 08:40 AM.
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Old 08-27-2017, 06:34 AM   #17
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Default Re: 8BA clutch finger adjustment

Just as a relatively minor shim thickness change can be significant to lever height, so too is any compressed clutch disc thickness variations. The Ford spec called for differing thickness solid plates for each diameter clutch with adjustments gaged from the PP cover.

Frankly I doubt the heights could be so far off as to cause the clutch to fail to release or engage. You should do what you are happy with whether it is right or not.
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Old 08-27-2017, 07:16 AM   #18
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Default Re: 8BA clutch finger adjustment

It will not fail to release or engage, the point is to eliminate any possible means of chatter so there is equal pressure all around while the disc is slipping during the engagement procedure.

Quote:
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Just as a relatively minor shim thickness change can be significant to lever height, so too is any compressed clutch disc thickness variations. The Ford spec called for differing thickness solid plates for each diameter clutch with adjustments gaged from the PP cover.

Frankly I doubt the heights could be so far off as to cause the clutch to fail to release or engage. You should do what you are happy with whether it is right or not.
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Old 08-27-2017, 08:05 AM   #19
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Default Re: 8BA clutch finger adjustment

Thank you, Mr. Miller.
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Old 09-01-2017, 10:00 AM   #20
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Default Re: 8BA clutch finger adjustment

Thanks to "Ross F1", who sent me some nice stainless steel shim stock, I was able to get my clutch fingers all within .010" of each other. One required .007" while a second needed .002". I think the .010" is about as good as can be done because of the geometry of the clutch fingers. The hardest part of the whole thing was drilling the holes in the thinner shim stock. I ended up punching them with a one of the hollow punches I have for making gaskets. (I think it needs to be sharpened now.) Thanks Ross, and also "Fordors" who set me on the right track.

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