clutch pivot ball height check - Page 3 - Chevelle Tech
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post #31 of 50 (permalink) Old Feb 22nd, 20, 10:16 PM Thread Starter
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Re: clutch pivot ball height check

Did I mention that this clutch is kickin' my a$$!

(BTW - I have my pivot ball installed without any spacer shims under it, so it is at "factory" height).

So today I installed the McLeod adjustable TOB with 1 spacer shim in it. This one spacer in the TOB moved the fork so far forward that it is ~almost~ touching the bellhousing opening up front. (So far forward that I don't think I could even try to install the TOB with 2 shims). I thought to myself this was too far forward to the point where I wouldn't be able to get any freeplay at the top of the pedal, and that maybe I should put a shim back under the pivot ball..... but I didn't. I said; what the hell - go for maximum movement, leave it like this. Well, turned out I was able to adjust to get a little freeplay on the clutch pedal, albeit with the fork ~almost~ in contact with the bell opening.

Started the car and still not disengaging! When under the car and over stroked the clutch adjustment by a 1/4 inch longer than "stock" setting. This forced the TOB into the PP fingers with the clutch pedal at rest, therefore partially holding the fingers inward all the time. Now the clutch will disengage. No problem getting into reverse. Appears I am still not getting enough stroke out of my stock Chevelle components...


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post #32 of 50 (permalink) Old Feb 23rd, 20, 3:10 AM
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Re: clutch pivot ball height check

If your clutch for angle is forward of 7 degrees then it's just as bad as being back too far. Your clutch fork at 90 degrees should be real close to the half way point of your available pushrod travel. If I remenber correctly the typical clutch needs about a half inch of travel at the fingers to disengage. Your clutch fork is a 2:1 ratio, so you need an inch of movement from finger engagement to release the clutch. Clutch finger movement to completely disengage a clutch may vary between pressure plates.

Which bellcrank did you go with?

Many repops have the levers off by 10 degrees or have incorrect hole spacing or lever lengths. All of which can affect the available throw. I prefer stock or rebuilt stock bellcranks to the repops for this reason.

I'll double check measurements of the clutch bellcrank in my 70 in the am. The 67 actually had 3 different available bellcranks. One for small block and a 1st design, which is the same as 66 and a later design mid year. I think the difference in the 1st and second designs was only in the shape of the upper arm bend and the way it was attached. I think the actual functional geometry was the same.

Did you ever check the thickness of the clutch pedal stop? 3/16" is what you want and this does put the clutch pedal higher than the brake pedal which is how they came out of the factory. If you see a stop that is 3/4 inch thick, it's a repop from a Chevy truck stop which is what many of the repops were modeled from.

Before you rip into it, duplicate your measurements as in post 21 and 26 and we'll see where you ended up. Pictures of your clutch fork angle during the process might help.
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post #33 of 50 (permalink) Old Feb 23rd, 20, 3:19 PM
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Re: clutch pivot ball height check

Let me jump in here and say that I am the Corvette guy that Al referenced in the earlier thread. With Al’s help I got it perfect. My fork is almost touching my Lakewood as well. Now since you are using the Corvette fork, I don’t know if this could be an issue for you, but in C2 and C3 Corvettes, if a clutch doesn’t release in .550 of an inch, it won’t release as that is how limited the travel is. There is a guy over at Corvetteforum who has tested a bunch of off the shelf clutches on a press, and found many don’t release within this range of travel. I know this was mentioned in that thread, but wanted to bring up this subject again. I had tried the McLeod adjustable bearing and found even at its shortest length was too long. I am using the stock for Corvette 1.25 inch throw out bearing and McLeod adjustable pivot ball. I know how frustrating these problems can be.

Bill
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post #34 of 50 (permalink) Old Feb 23rd, 20, 10:49 PM
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Re: clutch pivot ball height check

Quote:
Originally Posted by 69ttop502 View Post
Let me jump in here and say that I am the Corvette guy that Al referenced in the earlier thread. With Al’s help I got it perfect. My fork is almost touching my Lakewood as well. Now since you are using the Corvette fork, I don’t know if this could be an issue for you, but in C2 and C3 Corvettes, if a clutch doesn’t release in .550 of an inch, it won’t release as that is how limited the travel is. There is a guy over at Corvetteforum who has tested a bunch of off the shelf clutches on a press, and found many don’t release within this range of travel. I know this was mentioned in that thread, but wanted to bring up this subject again. I had tried the McLeod adjustable bearing and found even at its shortest length was too long. I am using the stock for Corvette 1.25 inch throw out bearing and McLeod adjustable pivot ball. I know how frustrating these problems can be.

Bill
Hi Bill, glad to hear that your clutch is working well. David is using the correct #3892632 Clutch Fork for his Chevelle. He wisely decided not to run the Corvette clutch fork which would have cheated him out of even more available throw as the effective lever length is longer than on the Chevelle fork.

Your Corvette crowd that needs more throw might benefit from relocating the pushrod hole on the clutch fork inboard by 1/2 to 5/8 of an inch and elongating the pushrod clearance slot. No free lunch though. This would decrease the leverage ratio and result in a stiffer pedal.
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post #35 of 50 (permalink) Old Feb 23rd, 20, 11:07 PM
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Re: clutch pivot ball height check

David, I took a look at my 70 and the measurements are the same as these listed at https://www.4speedconversions.com/3920615.html. I cannot at the moment measure the angles of the Zbar, I can't find my protractor or angle finder. Probably in my work toolbox. When I get the tools I'll check the angles.

Check your clutch fork angle. 5-7 degrees is the target. Too far ahead or too far behind and you'll lose throw.

Since I don't know what Z bar you have, I'll post up some info so maybe you can figure out where the issue lies. There are also 2 pedal rod lengths available for 67. Read to the bottom of the comments section on the 4 speed site pages.

https://www.4speedconversions.com/67...e_linkage.html

https://www.4speedconversions.com/3920615.html

https://www.4speedconversions.com/3872895_r1.html

And also a thread on the 67 z bars and pedal pushrods in the sticky section on this site:

https://www.chevelles.com/forums/33-...oem-repop.html
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post #36 of 50 (permalink) Old Feb 24th, 20, 5:52 PM Thread Starter
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Re: clutch pivot ball height check

I do believe I have the correct repo bellcrank and linkage for my '66. (3872895 z-bar) I am on my second bellcrank - one came from 4speedconversions and one came from Ground Up, and they are both the same part. The pedal to bellcrank arm came from 4speedconversions (9774625) and according to his info; this one is correct too. ( I do not have original parts like these to compare with) The linkage to the bellcrank performs spot on, and the bellcrank appears to look like the pictures I've seen online as to what an original looks like. I stayed away from the 67 parts because they were designed to go around the '67 crash absorbing steering column, and I do not have that on my '66.
When this early z-bar is on the car; the lower arm comes VERY close to the oil sending port - and here I have a "bigger than a stock sending unit" 90* elbow for a mechanical oil line. In an effort to stay away from the oil fitting; I cut the welds for the lower arm and rewelded it back on, only rotated a little farther away from the oil fitting..... which located the linkage a little lower than the factory placement. Since I ran into clutch disengagement issues; I removed this modified z-bar and replaced it with the second un-modified z-bar. So now for all this work I've been going through in order to make this clutch work; I have what I believe to be all stock factory components - albeit the z-bar and its pedal linkage are repos.
And I do have the 3/16 factory rubber bumper.


Quote:
Originally Posted by 69ttop502 View Post
There is a guy over at Corvetteforum who has tested a bunch of off the shelf clutches on a press, and found many don’t release within this range of travel.
Thank you, Bill. I searched and found the Corvetteforum thread about testing various clutch packs for release points. Very interesting. I did this travel test to my new Hays clutch, and it is so very close to meeting the proper .050" disengagement feeler gauge in at a .500" stroke, but it doesn't it. Too tight. I can push down on the PP to about .580" and then I get a good feeler gauge reading, but since our maximum available stroke on or linkage is reportedly at .580" - this .580" is not achievable on the PP when you factor in the proper pedal end play at the pedal in order to not have the TOB riding the PP.

The next thing I'm going to do is remove my tranny so I can get an accurate distance measurement at the TOB end of the clutch fork. I'm going to measure clutch pedal up and clutch pedal down to see if I am actually getting .580" travel at the TOB or not.


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post #37 of 50 (permalink) Old Feb 25th, 20, 10:48 PM Thread Starter
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Re: clutch pivot ball height check

So I pulled the tranny and removed the TOB in order to measure clutch fork travel at the TOB end. My wife operated the pedal while I measured with the clutch pedal fully up and fully to the floor. Measured again and again, and got the same result; the TOB end of the clutch fork moves ~.700~! Holy crap - that's more than I expected based on what I've been reading. Mathematically that should be enough to get clutch disengagement..... but not on my clutch.

So I removed the bellhousing, placed it perfectly level (used a bubble level) on a flat table with the engine mounting side facing up, and kept the fork installed on the pivot ball, but no TOB. Then I used a small level across where the TOB would reside to keep the fork level, and I used a magnetic angle gage on the top of the fork - located on the inboard side of the fork; over the pivot ball area. This was as close of a area that I could find to get a reading of what angle the fork would reside. Then I tilted the fork upwards toward the engine mounting side of the bell and measured the outermost end of the fork. At +5* - the fork was 2.375" down from the engine mounting surface of the bellhousing. Next I tilted the fork back to a negative 5*, where I now have a measurement of 3.75" down from the mounting surface. (so a total of 10 degrees travel).

3.75" minus 2.375" equals 1.375" of travel. Since our forks provide a 2:1 ratio in movement - this 1.375" of travel divided by 2 equals .6875" travel at the TOB, which is as good as my previous eyeball physical measurement of .700" travel!

Now what?.....Did I mention that this clutch disengagement issue is kickin' my a$$?


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post #38 of 50 (permalink) Old Feb 25th, 20, 11:26 PM
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Re: clutch pivot ball height check

Geez! I'm following along , mum, as I cant add a thing to what you've been doing.

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post #39 of 50 (permalink) Old Feb 25th, 20, 11:29 PM
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Re: clutch pivot ball height check

Quote:
Originally Posted by RAIDER SS View Post

Now what?.....Did I mention that this clutch disengagement issue is kickin' my a$$?
Mine too. I'm hoping someone will jump in here and shine some light on what I'm missing here.

The clutch disc came with the pressure plate?

I would probably pull the flywheel and mount the disc and pressure plate. Then put the unit in a press to see how much throw is required to get a complete release. I think you already did this and came up with .580. So keep digging.

Something is not adding up here, I'm not seeing it and it's buggin me. Check to make sure the Marcel on the disc is not bent and all the fingers on the diaphragm are at the same level, none out of place or bent.

From your earlier measurements, I figured you would have about .625 at the throwout bearing. I saw 1.25 throw at the pushrod end divided by 2. This should be just enough to get the job done and still have a minimal airgap.

I wonder if you're losing actual throw through deflection of any of the components. The numbers you are seeing are unloaded numbers. I remember Hays had a memo or instructions out to gusset the bell crank at one time..........Just brain storming out loud....
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post #40 of 50 (permalink) Old Feb 25th, 20, 11:30 PM
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Re: clutch pivot ball height check

Quote:
Originally Posted by 427L88 View Post
Geez! I'm following along , mum, as I cant add a thing to what you've been doing.
COME ON GENE! Throw us a bone!
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post #41 of 50 (permalink) Old Feb 25th, 20, 11:39 PM
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Re: clutch pivot ball height check

This is where I saw the bit on the deflection.
Attached Files
File Type: pdf HAYS INSTALLATION INSTRUCTIONS CLUTCHES AND FLYWHEELS.pdf (276.4 KB, 10 views)
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post #42 of 50 (permalink) Old Feb 26th, 20, 6:12 AM
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Re: clutch pivot ball height check

Thats for a Ford clutch fork tho. the oem bellcrank was replaced on my car due to "permanent deflection" over the years. A good buddy, a tech, here caught that. Said the cltuch felt "bind-y" . A new fork from Hinshaw's cured it. As you have multiple forks to choose from, we ASSUME its not the bellcrank itself.

I promised a kid, the son of one of my best Chevelle buds who passed last year, that I'd come up Sat and help him fix a clutch problem on his 69 that has dogged his dad from day one.

Now I'm scared to! Maybe I simply got lucky on my setup. David, since you've become so intimately familiar, care to ride with me to Toronto Saturday am!? And once we get Ryan's clutch set, then next weekend I'll drive back to my hometown and see if two sets of eyes can fix yours? I'm kidding!

Back to questioning assumptions, , originally a 4 speed car? ( questioning the position of the frame mount). I know my pedals were removed at one point, as the clevis is in the wrong position, but it hasnt affected geometry, afaik.

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post #43 of 50 (permalink) Old Feb 26th, 20, 8:23 AM
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Re: clutch pivot ball height check

I can't follow all the changes from this thread so I will ask basic questions. with the pivot at 4.80" from the block and using the 1.345" throw out bearing-what is the result? fork hits bellhousing hole? or not enough finger release travel? some other linkage issue?
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post #44 of 50 (permalink) Old Feb 26th, 20, 11:00 AM
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Re: clutch pivot ball height check

could be a bad pp from the factory i would send it back and have them check it. i had the same problem as u but i had all zoom set up , i got so disgusted i took every thing out and went with all stock flywheel clutch and pp. works great now. i as u did not have nothing but the clutch pedal u might want to consider going back to stock
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post #45 of 50 (permalink) Old Feb 26th, 20, 11:02 PM Thread Starter
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Re: clutch pivot ball height check

I do appreciate all the help you guys are giving me. This is quite the exercise to get to the bottom of my clutch issue.

My ‘66 was originally a Powerglide car, and I have converted it to the Muncie 4 speed. As far as the bracket on the frame; I didn’t think the assembly manual gave me accurate enough numbers to properly locate the frame bracket, so I located it another way. I installed the BB motor and tranny into the car using its installed motor mounts and tranny mount just as in a completed car. (using tranny support brace too) Then I screwed a threaded rod into the pivot ball mount on the block and shortened the rod enough to where I can clamp the frame bracket to the frame in front of it, whereas it is aligned exactly with the center of the threaded rod end. Welded it there. Turned out perfect, as my bellcrank is perfectly level with the motor / tranny fully installed.

Now I have a little back story. I bought a Hays clutch kit and new flywheel last summer and installed it into the car. (China mfg.) I used the corvette fork, but the only way I could get clutch disengagement was to have the TOB ride the PP 100% of the time. So this enabled me to shift the car normally. But the problem I had was that this clutch chattered REALLY bad. But my goal was to put some miles on the car before the snow flew, so I accomplished that with this chattering clutch. Maybe put 100 miles on the car to see if there were other issues that needed attention besides the clutch. This winter I tore out the clutch and found a HEAVY burn mark on the flywheel, and the same HEAVY burn mark on the PP – at the same location opposite the flywheel burn mark. Guess I found the chatter issue, eh? Called Hays several times, and eventually they sent me a new clutch kit and a new flywheel. (USA mfg. this time) This new clutch and flywheel is what I have been having SO many issues getting clutch disengagement.

So clutch & flywheel #1 (with the burn marks) Is what I tested with the press to see how much travel netted me .050” clearance – and the answer was just over .580” travel on the PP.
So clutch & flywheel #2 (replacement) is what has been in the car for all this disengagement problem. I took it out of the car today and did the press test to see how IT performed. Holy crap – this clutch is way worse than clutch #1! I had to compress .550” before I could even get the disc to spin at all, and it took .700” of travel in order to get the .050” feeler gauge in there! Gawd I hope this is the assignable cause….

So now I have a brand new McLeod clutch kit today and I’ll report back on what I find with it. Hopefully tomorrow…..


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