OkeeGuy

ok...i have compared my pressure plate and throw out bearing thickness to other "known" corvette pressure plates and bearings and they ARE THE SAME.
2 1/2" & 1 1/4" respectively...
AND...my clutch kit is DEFINETLY for a 1979 corvette...

but the fact still remains that when installed my adjustment is all the way at the end...i mean flush with the end of the rod!
so i asked my freindly parts guys if there is a thicker (longer) throw out bearing available and there is one...
it fits 1955 covettes and also late model camaros...every dimension is identical except for the length...
it is 9/16" longer...
is this the answer?

69 N.O.X. RATT

I had sorta the same problem. I welded an extra inch of bar on the the clutch rod and therefor gained an extra inch of adjustment.

OkeeGuy

thats kinda what i was gonna do til i mentioned it here and almost got crucified for it! :lol:
"if your adjustment is at the end then you have other problems...fix the problems"
i gladly would fix the problem if i only knew what the problem was!:yesnod:

i just dont get it...everything measures the same...why should it be different at the rod? it just bugs me to no end not knowing! :mad
i think im gonna go with the longer throw out bearing and forget about it...

jyounane

Hi,

I didn't read previous threads, so I'm assuming you've got a stock setup.

I had a similar problem with mine....insufficient adjustment AND the clutch fork was hitting the firewall before the clutch disengaged!

The answer was a longer clutch fork pivot ball in the bell housing, readily available. This is needed if you've machined a bit off the flywheel AND you've got a new clutch plate which both work against you.

I was convinced I'd been sold the wrong clutch kit, and even put the old one back in only to have the same problem!

Marginal GM design. Others may have seen this problem and can help also.

Good Luck,
Joe

OkeeGuy

i find that amazing and after what ive experienced lately...
VERY BELIEVABLE! :yesnod:

yes i DO have a stock set-up and i find this kind of a mystery...
how much longer is the ball stud?
where do i buy one?

thanx alot jyounane :)

427Hotrod

GM Basically used three pressure plate setups over the years. There is a regular "flat" diaphragm, there is a "raised" diaphragm and then there is the 3 finger "Borg& Beck"type.

The flat one takes the long throwout bearing. The raised one and the Borg& Beck take the short one.

There are also two different studs that go into the housing. 90% of the time you use the shorter one with the raised and Borg& Beck types.

If it was all working otherwise when you took it apart, something has changed. Look real close at the two pressure plates as they lay on the table side by side. The raised part is in the center area. NOT the main part of presure plate. The fingers of the diaphragm rise to a pretty pronounced cone. The flat one has a very slight rise to it. The height of the fingers in the center barely extend pat the top edge of the pressure plate. Lay a straightedge across the fingers where the throwout bearing presses.

Either the old clutch was a raised one/Borg&Beck and the new one is a stock replacement flat one, or something else has moved. Any chance you have multiple holes in the linkage and got the wrong one?

Make sure throwout arm is on stud right. With linkage unhooked, as you look up at it....lightly push the arm rearward(just as linkage would do) until the bearing just touches the pressure plate. At this point the arm should be still pointing forward to the front of the car. It will never work properly if it goes over center toward the rear. You want it as far forward as possible and not have it touch bellhousing opening. You only need a little clearance to get freetravel.

If something has changed, you will need to juggle studs to get bearing closer to pressure plate. Seldom will the long one fit in there even with a short stud with a raised diaphragm clutch.

The raised type is better by the way. It holds much better than the flat type.


Hope this helps,


JIM

Clink69

To get it perfect you can put in an adjustable ball stud. Get the adjustment right then locktite the ball stud nut so it doesn't come loose. Steve straus had a posting a month ago on this... With picks. I am dealing with a simialr issue now with my free pedal adjustment and a sticking rod...

You ever jump out that basket?

Chris
:flag

jyounane

From memory, it was only like 1/8" or 3/16" longer, but the lever effect of the clutch fork multiplies that quite a lot at the pushrod.

I got my advice and the pivot ball stud from Corvette Clinic in San Jose Ca. Talk to Matt or one of the guys there, they are very knowledgeable. (408) 295 9300.

No doubt there are other sources, but Matt is still worth a call to talk about your problem. By the way, did you have your flywheel machined?

Best regards,
Joe

lbell101

Also make sure the trhowout bearing itself is installed correctly. The whole fork goes into the groove. Not the fork on one side of the flange and the fork spring on the other.
Also make sure the spring from the firewall to the clutch linkage is not missing.

PRNDL

Not sure if you saw my temporary/bubba solution to the same problem. I have an adjustable clutch fork ball stud that might go in some day, but meanwhile i now have plenty of adjustment on the rod, the right amount of freeplay and the clutch is much easier to use - I am just a little afraid to push the clutch pedal to the floor! BTW, this is a very very common (almost universal) problem with replacing the stock clutch with a centerforce clutch. :) MJ





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jyounane

Thanks for the photos. I can see that would work OK in your case.

Part of my problem was that the end of the fork was hitting the firewall before the clutch disengaged, so I needed to bring the end of the clutch fork forward. This is why the longer ball stud worked nicely for me.

Best regards,
Joe

OkeeGuy

thanx for all your help Jim and everybody...
Jim, are you saying that the longer throw out bearing will not fit?

MasterDave

This is what I found out on mine. The clutch fork pivot ball had backed out to the transmission. That's prolly 1-2 turns. Also the pivot ball on the engine bell crank was loose. Couple that with elongated holes in the clutch rods and a loose mechanism up under the dash and you won't be able to disengage the clutch. Make sure all is tight first.

Surfer69

You want to make sure to use two (2) springs on lower rod. If you leave out spring that connects to fork, you loose some rod adjustability from any slack not taken out at fork by spring. Dont ask how I know that.

OkeeGuy

everything is tight and all springs are intact...
i think i will lengthen the rod...
i heard once that there is a longer rod available...
anybody know about this?

PRNDL

The reason I had an extra rod to cut up and lengthen is because when I ordered it I THOUGHT it was longer than the stock rod I had on the vette, but when I got it (as you can see from the pic) it was identical. :) MJ

lars

Gary -
We run into this all the time when changing clutches out here. We solve the problem in one of two ways:

1. Easiest way is to simply install an adjustable fork pivot ball when doing the clutch work. Run the adjustable ball up about 1/8" taller than the stock ball, and you will have adequate adjustment. However, if you already have everything assembled, this isn't too practical...

2. Lengthen the stock lower clutch rod by 1-3/4". If you don't have good welding experience, measure your rod and determine how much longer it needs to be in order to get the adjustment into the middle of the rod. Then send the rod out to me and I'll lengthen it for you. No problem.

3. Don't go to the tall TO bearing - it is usually too tall to work.

jyounane

Dear Lars,

I had the same problem and fixed it with the longer ball stud.

I could not use your 2nd method of lengthening the push rod because the outer end of the clutch fork was hitting the firewall before the clutch disengaged. (1969 M21 BB)

So the longer ball stud helped by moving the end of the fork forward.

I just wondered whether you'd encountered this problem also.

Thanks for your help.
Best regards,
Joe

OkeeGuy

hi Lars...thanx for your advise...yesterday i extended the rod and we will be reassembling the car tonight after the shop closes...
by the way...the carb rebuild is awesome...i especialy notice how easily it starts on cold mornings now...gary