V8 Clutch in Model A: Something is not right

[lyleknievel]

A while ago, I pulled the engine on my '29 Tudor, and took the occasion to have the flywheel modified and a V-8 STYLE PRESSURE PLATE (Bratton PART #: 11460) installed.
In the description it indicates "Uses the same clutch disk (11400) as the stock one".
I actually bought the clutch disk separately from Mac's (Model A, B and V8 Clutch Disc 1928-40, Part # 28-385984-1)
What I found was that the Clutch would not disengage.
The vehicle was parked for a while since I installed everything, and looking through posts/talking to people, I reasoned that possibly my clutch disk was stuck to the flywheel, and so I did the recommended process:
*blocked the rear wheels,
*put in 3rd gear,
*started the car so that wheels were turning,
*mashed in the clutch,
*put on the brakes.
When I did that, the rear wheels stopped turning, but there was a noise coming from the clutch and still it seemed that the clutch was not fully releasing (still grinding trying to go from neutral into gear with the clutch pedal down...
And so I took it all apart, and what I found was that the 3 fingers of the pressure plate were apparently scraping against the clutch disk.
This seems to me to be evidence that the clutch disk is too thick.
I have seen references that the Model A clutch disk is 0.340" thick -- and the clutch disk I am using (got from Mac's) is 0.380" thick.
And so this would explain why the clutch would not disengage, and when I made the adjustment to the clutch pedal in an attempt to get it to disengage, it actually drove the 3 fingers all the way into the clutch disk which was the noise I was hearing.

Any other ideas out there of what caused this and what to do to fix it?

[nkaminar]

Buy a V8 clutch disk. Make sure the fingers are adjusted correctly.

[bobbader]

Are you sure you installed the disc the right way? The splined collar in the center is offset. you may have the disc installed backwards. It may be an optical illusion, but your picture looks like the center plate of the disc is bulging as if it has been deformed.

[Flathead]

When you tighten up the pressure plate do the release fingers come close to the center of clutch disc not allowing much travel for clutch to release when stepping on pedal? If the disc is too thick this can happen. A work around for this is to put six good flat washers between the pressure plate and the flywheel where it mounts, one for each bolt. The thickness of each washer must be the same but sets of thinner or thicker will allow tuning your clearance. Maybe start with .040 thick to match the difference between your disc and stock. Or get a thinner disc.

[Tom Endy]

Originally Posted by bobbader

Are you sure you installed the disc the right way? The splined collar in the center is offset. you may have the disc installed backwards. It may be an optical illusion, but your picture looks like the center plate of the disc is bulging as if it has been deformed.

I think the disk was installed backwards also. In the third photo you can see witness marks where the throw out bearing was rubbing the disk hub.

Tom Endy

[Y-Blockhead]

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Most definitely the disk is in backwards.

[Rob Doe]

lyle,

I just installed a new Bratton's clutch disc in our coupe. The coupe has a modified flywheel and a v8 pressure plate. I initially had the precise experience that you describe.

I had initially adjusted the clutch free play of the pedal to 3/4". What I did to correct the issue was to double the free play to more like 1-1/2" or possibly a bit more. The coupe had a good bit of free play before putting in the new clutch which was also more than a stock Model A clutch.

Apparently, the V8 pressure plate has a different length of operational range of the fingers. The range seems to be shorter forward travel of the fingers to fully release the clutch disc. By increasing the pedal free play to a larger amount, a good portion of this excess range of the pedal will be consumed before the throw out bearing contacts the fingers, and the full travel will wind up withing the maximum travel of the V8 fingers and more than enough to release the clutch disc. (before the fingers move forward enough to contact the clutch disk and force it into the flywheel.)

With the viewing window open, you can watch the clutch disc springs spin with the flywheel. When you depress the clutch a small amount, they slow to a stop, but if you continue to fully depress the pedal, you can see them begin to spin again and make noise.

Increase the pedal free play to transition the max forward position of the throw out bearing toward the rear of the car. If I remember correctly, turn the fork lefty loosey, counter clockwise a few turns and retest while watching the clutch disc springs through the view window.

It was my first clutch install and this took me an full day to gather experience. Worn to a frazzle, I went home and slept on it. When I woke up I had the answer. We now have ~ 3000 miles on the clutch, and it's working nicely. It grabs near the top, no chatter etc.

[Bob C]

Originally Posted by Tom Endy

I think the disk was installed backwards also. In the third photo you can see witness marks where the throw out bearing was rubbing the disk hub.

Tom Endy

The marks on the disc are from the pressure plate fingers, see
the second picture.

[nkaminar]

Correct way to install clutch disk is shown here: https://www.snydersantiqueauto.com/p...9060&cat=41664

[Keith True]

How about a picture of the other side of that disc?I have an idea,but would like to see the other side first.

[lyleknievel]

Originally Posted by bobbader

Are you sure you installed the disc the right way? The splined collar in the center is offset. you may have the disc installed backwards. It may be an optical illusion, but your picture looks like the center plate of the disc is bulging as if it has been deformed.

disk was installed correctly -- disk is not bulging -- it is like brand new except for the scratches

[lyleknievel]

Thanks for the comments and ideas.

Clutch was not in backwards -- as you can see from the pictures, the side that was scratched from the pressure plate fingers is the Trans Side... here are pics of both sides of the disk, which, like I said, apart from the scratches appears to be like new (which it is new so no surprise there!)

[lyleknievel]

Originally Posted by Flathead

When you tighten up the pressure plate do the release fingers come close to the center of clutch disc not allowing much travel for clutch to release when stepping on pedal? If the disc is too thick this can happen. A work around for this is to put six good flat washers between the pressure plate and the flywheel where it mounts, one for each bolt. The thickness of each washer must be the same but sets of thinner or thicker will allow tuning your clearance. Maybe start with .040 thick to match the difference between your disc and stock. Or get a thinner disc.

On the first picture with the pressure plate mounted to the flywheel, you can see where the fingers are with the pressure plate tightened to the flywheel -- and yes they are fairly through their "stroke" which limits the amount that the release bearing can push. I did think about "install washers between the pressure plate and the flywheel" idea and I think that will probably work but for $50 maybe I'll just get the thinner disk (assuming that is the right answer).

[rotorwrench]

I noticed that the disc in the Snyder's description captures the torsion springs in a different manner. The OP's disk has the raised lips on each side of the spring where the finger adjusters made contact. The disk in the Snyder's description doesn't have those raised lips.

Modern reproduction stuff is generally always different than the original Borg Warner stuff.

[Phil Brown]

Looks like the spring center hub stands very proud of the clutch center steel disc. Might just be the angle of the pic.
I checked a used disc that was on the shelf and it is only 3/8" as seen in the pics. That might be creating your problem if that distance is larger

[lyleknievel]

Originally Posted by rotorwrench

I noticed that the disc in the Snyder's description captures the torsion springs in a different manner. The OP's disk has the raised lips on each side of the spring where the finger adjusters made contact. The disk in the Snyder's description doesn't have those raised lips.

Modern reproduction stuff is generally always different than the original Borg Warner stuff.

I saw somewhere that the raised lips were added due to springs jumping out and creating havoc in the other design...

[lyleknievel]

yes it is 3/8" -- same as the one you are showing

[lyleknievel]

Originally Posted by Phil Brown

Looks like the spring center hub stands very proud of the clutch center steel disc. Might just be the angle of the pic.
I checked a used disc that was on the shelf and it is only 3/8" as seen in the pics. That might be creating your problem if that distance is larger

mine is 3/8" -- same as the one you show in the picture

[johnneilson]

From the first picture it looks like the pressure plate is compressed too far, disk is too thick. It is positioning the arms too deep into the PP assembly, no room to actuate and release the clutch.
There are a couple causes, as I think your .380 dimension is about right for the disk.

I have not seen any issues with the pressure plate itself, only the fulcrum points on the release levers. Take a look in there and see if there are shims or washers between the pivot and the outer housing. I know there are at least two different height cover plates and pivot fulcrums.

Do not attempt to disassemble this assembly unless you have some sort of a press to contain the spring preload.

I would not add washers under the PP to flywheel to run, but you can try this to see if you can get the height correct where the arms can move to release and clear the disk.

The other option might be to run a solid disk, non spring center disk.

John

[lyleknievel]

I do not see any shims, etc., here are pics looking at the pivot arm