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03-30-2024, 02:02 PM | #1 |
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V8 Clutch in Model A: Something is not right
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? |
03-30-2024, 02:39 PM | #2 |
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Re: V8 Clutch in Model A: Something is not right
Buy a V8 clutch disk. Make sure the fingers are adjusted correctly.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
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03-30-2024, 03:45 PM | #3 |
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Re: V8 Clutch in Model A: Something is not right
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.
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03-30-2024, 03:53 PM | #4 |
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Re: V8 Clutch in Model A: Something is not right
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.
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03-30-2024, 04:06 PM | #5 | |
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Re: V8 Clutch in Model A: Something is not right
Quote:
Tom Endy |
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03-30-2024, 04:10 PM | #6 |
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Re: V8 Clutch in Model A: Something is not right
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03-30-2024, 04:19 PM | #7 |
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Re: V8 Clutch in Model A: Something is not right
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.
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03-30-2024, 04:53 PM | #8 |
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Re: V8 Clutch in Model A: Something is not right
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03-30-2024, 04:58 PM | #9 |
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Re: V8 Clutch in Model A: Something is not right
Correct way to install clutch disk is shown here: https://www.snydersantiqueauto.com/p...9060&cat=41664
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-30-2024, 05:51 PM | #10 |
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Re: V8 Clutch in Model A: Something is not right
How about a picture of the other side of that disc?I have an idea,but would like to see the other side first.
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03-30-2024, 06:01 PM | #11 | |
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Re: V8 Clutch in Model A: Something is not right
Quote:
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03-30-2024, 06:15 PM | #12 |
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Re: V8 Clutch in Model A: Something is not right
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!) |
03-30-2024, 06:37 PM | #13 | |
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Re: V8 Clutch in Model A: Something is not right
Quote:
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03-30-2024, 07:23 PM | #14 |
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Re: V8 Clutch in Model A: Something is not right
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. |
03-30-2024, 08:09 PM | #15 |
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Re: V8 Clutch in Model A: Something is not right
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 |
03-30-2024, 08:46 PM | #16 | |
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Re: V8 Clutch in Model A: Something is not right
Quote:
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03-30-2024, 08:51 PM | #17 |
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Re: V8 Clutch in Model A: Something is not right
yes it is 3/8" -- same as the one you are showing
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03-30-2024, 08:53 PM | #18 | |
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Re: V8 Clutch in Model A: Something is not right
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03-30-2024, 09:06 PM | #19 |
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Re: V8 Clutch in Model A: Something is not right
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
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03-30-2024, 10:03 PM | #20 |
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Re: V8 Clutch in Model A: Something is not right
I do not see any shims, etc., here are pics looking at the pivot arm
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03-30-2024, 10:05 PM | #21 |
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Re: V8 Clutch in Model A: Something is not right
note on the second picture I removed the nut that was originally on that side, backed out the screw, and added a nut on the other side (which may or may not end up as the final configuration -- but at least this way I would not drive the fingers into the clutch disk, all other things being equal)
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04-05-2024, 08:13 AM | #22 |
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Re: V8 Clutch in Model A: Something is not right
Lyle, what is the status of your project? Any luck?
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04-05-2024, 11:30 AM | #23 |
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Re: V8 Clutch in Model A: Something is not right
get a disc that is the proper thickness, then no modifications are needed
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04-09-2024, 09:23 AM | #24 |
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Re: V8 Clutch in Model A: Something is not right
The measurement from the flywheel plane to the pressure plate plane (with no clutch disk installed) is ~ 0.140". I got a friend to measure the same dimension on his V8 pressure plate and it was 5/16 (0.313). I called Bratton's and the person measured one off the shelf and it was 0.185". And so if I take the bratton's measurement, that is still 0.045" more than the one I have. And the design of the fingers give about 5:1 ratio on movement of the throwout bearing to movement of the plate...which means my throwout bearing would have to move 0.225" farther towards the engine to get the same release of the clutch. And so this is enough to explain why the fingers were having interference with the clutch disk.
Bottom Line -- I think the V8 Pressure Plate Assembly that I have is not right. Bratton's agreed to exchange it for a new one, but I have already had this one balanced to the flywheel and so I am inclined to just shim the pressure plate out from the flywheel using some precision washers. I have not started that process yet, but that is what I plan to do at this point. |
04-09-2024, 09:48 AM | #25 |
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Re: V8 Clutch in Model A: Something is not right
It works.
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04-10-2024, 06:03 AM | #26 |
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Re: V8 Clutch in Model A: Something is not right
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Balance your Model A flywheel at Home! The portion of interest starts at ~ 14 minutes in. George mentions the relationship of the range of pedal movement as it relates to the range of the pressure plate finger movements. He is discussing the stock Model A setup, but it applies to the non stock, customization of using a modified flywheel dimension along with a V8 pressure plate. I've read that the collar on the end of the pedal shaft is not the sole player in the travel of the clutch pedal. A senior guru stated that the upper floorboard had a role in limiting that travel. I believe this is true of our coupe's functioning and a friend's coupe with a stock setup. Without the floorboard, the pedal goes all the way to the firewall metal. This may be further than with the upper board installed. Just a thought. Our coupe's functioning, with new Bratton's clutch disc measuring ~.375-.380 thickness with the used V8 pressure plate required additional free play at the top of the pedal to work correctly. When I had it at 3/4" free play, I had the same result that you had, and I could watch it happening via the inspection window. I'll be interested in your experiment moving the pressure plate farther away from the flywheel. I suspect that you will simply diminish the pressure that the pressure plate exerts on the clutch disc when the pedal is at the top of its range. A stock setup exerts 1200 pounds. I don't have enough experience to speak with any authority, but in IMHO, I'm thinking that the proper operation of your setup will require a proper adjustment of the free play. In other words setting the max forward position of the throw out bearing in the correct position of the min and max travel of the pressure plate fingers. I'll be learning with you as you report your findings. Luck to ya.
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"It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!" Last edited by Rob Doe; 04-10-2024 at 06:30 AM. |
04-27-2024, 05:49 AM | #27 |
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Re: V8 Clutch in Model A: Something is not right
lyle: where'd ya go, any progress?
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04-30-2024, 07:40 PM | #28 |
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Re: V8 Clutch in Model A: Something is not right
So...my analysis is that the pressure plate was not allowing the clutch to properly release -- not enough stroke to adjust the pressure plate to release the clutch disk...
I could have just swapped out the pressure plate, but since this one was already balanced to the flywheel I was reluctant to do that. And so in the end I simply installed washers between the pressure plate and the flywheel, adjusted the fingers according to the specs, and put it all back together and everything is working fine. Per the guidelines, I adjusted the pedal so that there is about 1" pedal travel before the throwout bearing is contacted. The clutch totally releases with the pedal down to the floor, clutch is fully engaged when the clutch pedal is released...so all good! |
04-30-2024, 07:59 PM | #29 | |
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Re: V8 Clutch in Model A: Something is not right
Quote:
I bought more washers than needed, then checked thickness of each one to make sure they were all within 0.001" -- most of them were and so not much sorting was required...(the washers were from Lowes btw). |
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05-01-2024, 09:55 AM | #30 |
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Re: V8 Clutch in Model A: Something is not right
How thick was each stack of washers?
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05-01-2024, 03:13 PM | #31 |
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Re: V8 Clutch in Model A: Something is not right
as mentioned, the washers were 0.069" thick -- I only used a single washer at each screw and so the effect was that the pressure plate was 0.069" farther out from the flywheel vs. what it was previously.
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05-02-2024, 10:28 AM | #32 |
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Re: V8 Clutch in Model A: Something is not right
Thanks
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