ghostrider20

I installed a new centerforce clutch system and here is the problem:

(here are the centerforce numbers, centerforce say's these are the correct)
Pressure Plate # CF361675 (10.5")
Disk # 383271
Throw-Out-Bearing (self aligning) # N1716

The clutch pedal has about 3/4 of it travel that is free, (it does not just fall to the floor, there is pressure from linkage and springs, just no clutch pressure) and the last 1/4 starts to disengage the clutch, and the fork is moving full travel through out the entire clutch pedal event.
The fork cannot go back any further or it would hit the tunnel wall.

The adjustment rod is is at it's end.

I replaced the clutch fork pivot stud in the bell housing and it is the same size as the one that came out.

Plus when the clutch is pushed to the floor and starts to disengage (what little it does) there is a raspy noise comming from the bell housing? Of course because of the limited amount of disengagement I am not sure if it is normal break-in or not. It sounds like those funky weights and wire loop things on the pressure plate fingers.

I would like to check these numbers to verify that they are correct to eliminate that varible. (for a 1965 327/365shp with close ratio muncie).

M-21 close ratio: 10 spline
Muncie # 3851325
Tag Number #(857579)
Tail shaft number # 385758GM

Bell Housing (Aluminum) # 3858403

stock shifter and linkage. Linkage all intackt and in good working order.

My only thoughts are that the throw-out bearing is to short. It is 1/16" of an inch shorter then the one that came out. Centerforce says this is because the fingers on the pressure plate are 1/16" longer then stock.

Mark


[Modified by ghostrider20, 11:49 PM 7/12/2002]


[Modified by ghostrider20, 12:00 AM 7/13/2002]

Milehigh66

Mark,
Did you replace the throw out bearing? they make a raspy noise. My clutch also came out in pieces, really pathetic how bad it was. (from previous post) Is anything bent at all, Like the clutch push rod? I assume someone had the same problem once on my car because bubba made an adjustable rod that pushes the clutch fork. I would check all of your linkages real carefully first.

Kurt :cheers:

ghostrider20

Thanks Kurt,

The linkage worked before just fine, although the linkage was adjusted almost to the end before I started the project, so I only had about 1/2" of adjustment to use up. The linkage all looks good, nothing bent, missing or broken. I referenced the shop manual and the linkage looks good. If the linage were bent, the fork would not go full travel, and it is going full travel.
If the fork were bent, it sure is not obvious. I inspected it very carefully and can see no tweeking or bending. Although I have nothing to compare it to.

Mark

Milehigh66

I don't have the answer you seek grasshopper, I just hope that I don't have the same problem when mine goes back together. If it is not slipping and disengages all the way than maybe that is the way it is supposed to be?

Kurt :cheers:

ghostrider20

It cannot be the way it supose to be, (in a perfoect world maybe) because I cannot get enough "meat" to disengage the clutch far enough to get the car in gear!.

Thanks guys.
Mark

Milehigh66

If you cannot get enough meat to get it in gear than you are going to need more rod! you will have to lengthen something to gain more travel. Of all of the things that bubba did on my car (and there are plenty) the adjusment rod was well done and pretty ingenious. you are going to have to find the adjustment somewhere. I would call centerforce and ask them for suggestions, I'm sure this isn't the first time that they have heard this problem.

Kurt :crazy:

ghostrider20

I think is what I will have to do on Monday is re-install the clutch/pressure plate and mount the bell housing. I will leave the tranns down and look in the back to see exactly what is happening in there.

Mark-

SWCDuke

For reference from my '77 vintage parts catalog, the second design '55 to '63 release bearing is 1/1/4" long and the '64 to '78 is listed as 1/7/32" long. I think I recall Joe Lucia stating that the 1 1/4" release bearing is no longer available, but that 1/32" change would not be enough to account for your problem.

The '63 to '68 pressure plate is the same; '63 to '68 cover appears to be the same, but there is some ambiguity. The pressure plate and cover are listed separately rather than as an assembly.

The '63 to '68 SB flywheel is the same with a casting number of 3791021.

So far the only difference appears to be the 1/32" difference in release bearing length.

The '63 to '66 cross shaft is the same exept for big blocks and it changed again in '67 to cover all applications through '78.

The '63 to '67 upper pushrod appears to be the same for SBs.

The '64 to '67 lower rod is the same for SBs and is listed as 10 9/16" OAL. The '63 pushrod is not listed,and I know it was unique to that year with just one spring retainer. I measured mine on the SWC and it looks to be about 11 1/2" OAL.

Go figure!

The '63 release fork and bellhousing are unique. I don't know about dimensions relating to the linkage geometry, but the '63 fork had a ball socket to match the ball on the lower pushrod. The later models uses a different interface design between the lower pushrod and fork.

Duke




[Modified by SWCDuke, 5:48 PM 7/12/2002]

Jim_C

ghostrider20
I used the same centerfource clutch with good luck. I did find that the new pressure plate was thinner than the stock plate. I think ( if my memory is correct ) that the measurement from crank flange to friction surface is supposed to be .95 inches. I just happened to measure my new pressure plate which showed .85 inches. I called centerfource and they said the tollerance was .81 to 1.00, mine was in spec. I used a lakewood adjustable fork ball stud and adjusted it to make up for the thinner pressure plate. If your dissengage point is not in the middle of the pedal you can use the adjustable ball stud to put it there.
CUL Jim

ghostrider20

I layed the new and old pressure plates on a flat surface and mesured from the bench to the top of the fingers. The old and the new are the same height.

Here is an after thaught.

1: I was racing when this happened and was mashing the clutch pedal pretty hard.

2: I had no clutch ability after the race, had to shut car off, put car in first gear and crank starter to get it rolling and going.

3: When old clutch came out, pressure plate was all intackt. No bent fingers.

4: The disc on the other hand was missing some sections of the contacting surface. If this were the reason the clutch is out, HOW then could I have driven the car home. It was not slipping or burning just no clutch action.

5: Now the clutch pedal feels much like the nite I raced, only that it has about 5% clutching action, not enough to get the car in gear or even stop.

6: I think the clutch was not out the nite I raced, only something is not activating the clutch fully.

7: I inspected the movement of the clutch fork and it goes all the way. So Why is it not working?

I am about ready to open up a vein here...

Mark

ghostrider20

Duke:

In my 1965 corvette shop manual supplement shows the 1-1/4" Throw-out bearing as used in 63-64-65 as opposed to the 1-7/8" bearing. This must have been the sister bearing used often at that time and this was noted so the service tech would note the incorrect part.

This problem almost feels as though a longer throw-out bearing would fix the problem. But as stated the only one ever use in the SB mid years is the 1-1/4" with the respect to the 1/32" variable available today, which apears to cause no problem.

To bad the car is locked up at the shop for the weekend or I would install the bell housing and clutch linkage and map it out better.

Mark

Ih2lose

Mark
in the paragon reproductions catalog it states pg 34 paragon tec tip # 21 It may be necessary to remove the heavey over center spring clutch spring when using this clutchassembely.Due to centrifical force at high RPM ,the clucth pedal could stay on the floor .this condition only occors in 5% of the aplecations removal of the clutch spring eliminates this problem.the clutch they are playing thisd note on is a uk rep clutch plate.This is what I have in my car.
I had mentioned before I had a simular problem with mine a couple of saturdays ago(I have a trans oil leak that gets my clutch oily) I was taking a ricer for a ride and pulled out of my shop and dumped the clutch right away and it went up in smoke and stayed on the floor.I assumed it was covered in oil and I did not dry it off enough with a little use.any ways I rolled over to the side shut the car off .restarted it and the clutch pedal came back up to normal position and the car is very useable with a slight chatter in it.I will be pulling mine apart shortley to replace it and reseal the tranney.do you think this spring could be a possible problem? Mark is there any chance that you have the wrong fork or its is not clipped/snapped on the ball in the correct position? or it is bent improperley? My car is a 1966 with a m21 and a 427 can I measure any thing or take pictures of anything for you to compare it with yours? to make sure yours are correct I have plenty of adjust ment left on mine why would you be on the end?


[Modified by Ih2lose, 10:15 PM 7/12/2002]

ghostrider20

IH2Loose

Are the forks in question the same? If so a pic would be great. I was planning on going to the parts store on Saturday and comparing them, this is if the auto parts store carries them. Is the clutch fork a pretty common application amongst GM units? I am leaning towards the bent theory.

The car has basicaly the same problem I started with. (read thread "I Raced a Camaro and the Clutch went out") I feel that with the new clutch and disc, they are thicker and are allowing a fraction of clutching action. Nothing in the linkage seems bent though, and if it did bend, I doubt that it would bend so severly that all clutching ability would be lost.

If some one can verify the same part for the 66 BB fork and the 65 SB fork a pic would be great, or some measurements. Has anyone heard of a clutch fork bending? I have never heard of this, linkage maybe, but not the fork.

Centerforce Note:
What are the funky little weights and spring steel wire on the pressure plate fingers for??? I think those are the culprit for the raspy noise I heard when what little of the clutch disengaged.

Mark-

SWCDuke

Hey, Mark, you didn't tell me about THE RACE. :lol:

I'm beginning to suspect maybe something bent or broke in the linkage. Give everything including under the dash a very careful inspection.

The 1 7/8" release bearing is listed as the "first design" '55 part, but it was superceded during that model year with the "second design" 1 1/4" bearing, which carried through to '63 and was replaced by the 1 7/32" long bearing in '64, which carried through to the end of my parts book in '78.

Duke

P.S. I never bent my clutch linkage, but I DID bend the brake pedal pushrod to the master cylinder mashing on my J-65 manual metallic drum brakes. :)

magicv8

I had the same problem with an 11 inch CF a few years ago. I tried several fork pivots and made a custom one. Got tired of installing the 4 speed and put an 11 inch Camaro diaphram plate in. CF refunded my money. They know that some set ups are problems. Nothin works like GM parts.

SWCDuke

All '64 up to '78, the end of my book, use the same clutch fork - 3887159. The '63 does have a unique fork due to the the pushrod pivot design, but I suspect it is otherwise the same.

Give the clutch cross shaft a very close inspection to see if it is somehow got tweaked. Compare it to a known good one if you know someone locally with a midyear. The 63 to 66 SBs used the same crossshaft, 65-66 BBs have a different part number, and 67 up to the 78 limit of my book is a third part number.

I did have a clutch linkage problem once - the crosshaft ball stud in the block sheared off flush with the surface circa 1966. I was able to turn out the broken threaded remnant with finger pressure and put in a new one. Never had another problem with it.

Duke

Duke


[Modified by SWCDuke, 8:25 PM 7/12/2002]

ghostrider20

I have not inspected the cross shaft other then an eye over, although if it were sheared off it's mounts, would that not be very apparent. As I mentioned I feel although a linkage stress of bend would or should be very large and obvious to have 5 inches of pedal slap. I have not inspected the pedal assembly very closely. Although if this has any cause and effect, I sparyed White Lithium grease on the pedal assembly pivots as a lubricant.

The further I think and research this problem the more it is killing me to install the clutch components, bell housing, fork and linkage. Then stand behind the tranny hole with a flashlight and see what is going on in there.

MagicV8, was your application originally an 11" clutch or did centerforce send you the wrong one? How did you know what you needed? I am interested in some more details on your particular CF clutch events.

Mark


[Modified by ghostrider20, 6:14 AM 7/13/2002]

SWCDuke

With my "Mr. Spock" hat pulled down tight, the only logical conclusion I can come to is that there is something wrong somewhere in the clutch actuation linkage.

Duke

JohnZ

I doubt if the throwout bearing is the problem - all Corvettes use the same 1-1/4" OAL bearing. Make sure the bearing end of the clutch fork is installed properly on the bearing - the design allows it to be assembled wrong, with the curly ends on the fork engaging the flange at the rear end of the bearing - the curly ends and tension spring are supposed to be inside the groove, not over the flange. If the curly ends are over the flange, you won't be able to get the clutch properly adjusted - have seen many of these. Assuming the bearing is assembled properly to the fork, I'd suspect the fork may be bent.

TheOman

Here might be a piece of the puzzle. My car had the same issue with the adjustment rod way out at the end of the adjustment. The clutch that was in the car was brutal to push down.

Bubba had place the wrong rod between the fork and the Z-bar. The rod that I had was shorter than the correct lenght. You still have the issue of the noises and such but I would verify the lenth of that rod. If it is too short you are introducing another variable into the equation.

If I read this correctly you have the same problem just after the race and now. Can't be the clutch, my thoughts are that it was not the clutch after the race. Could something have happened under the dash where the linkage bolts to the pedal. There are two bolts up under there. If one broke the linkage geometry would change because the pedal and the sadpter plate would not be correctly oriented to eachother. Look at the manual. There are two bolts that attach a "bracket" to the pedal. Depending on which of two locations the bracket is attached to the pedal the actuation of the clutch is moved higher up toward the driver of further down toward the floor. If one bot is loose or broken things might have rotated to some sort of never never location where you cannot get enough disengagement.

Don't pull out that clutch till you look this over.


[Modified by TheOman, 10:58 AM 7/13/2002]