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New build, clutch isn't releasing (83 z-bar woes)

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New build, clutch isn't releasing (83 z-bar woes)

Old 02-09-2019, 08:04 AM
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New build, clutch isn't releasing (83 z-bar woes)

Long post, but please read it all before you reply! I cover most things in the post.

Did a V6 to V8 swap in my 83 Firebird. Kept the Z-bar setup since I found a good deal on the V8 bellhousing and fork and I don't mind adjusting things vs worrying about fluids.

Though the z-bar and fork are moving, it doesn't seem like enough. Clutch isn't disengaging fully and grinds when I try to get into any gear.

I've adjusted the pushrod far out as I could (5 threads left, far past reducing pedal free play) with no change.

I know the trans is good because I had it rebuilt and then drove the car I had it in before. I've had the cover off to inspect the guts and make sure everything moves freely.

Clutch and disk were from another car with about 3k on them. I didn't see any damage or odd wear.

New Centerforce N1716 throwout

New Clutch pivot ball GM P/N 3866568

Used Clutch fork GM P/N 5014090

These are the correct parts, right?

Wondering if they made different length throwout bearings?



And no, I don't want to convert to the hydraulic clutch. I like being difficult





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Old 02-09-2019, 08:20 AM
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Re: New build, clutch isn't releasing (83 z-bar woes)

You know, after some googling I think I answered my own question. Why on earth do I have a 70's 4 speed fork?? That's what was sold to me as being correct for the 83 but 5014090 doesn't come up with ANY thirdgen references.

ugh.

But, I'd still like to confirm with you guys. I don't have any idea; those two forks could be identical. I don't have it out to compare to proper one (14037647 or Dorman 14550)



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Old 02-09-2019, 08:48 AM
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Re: New build, clutch isn't releasing (83 z-bar woes)

Throwout bearing is on the fork correctly. This is a good thing.

I don't see a pilot bushing or bearing in your parts blowup.



This particular one is a bearing. A bushing is exactly the same except that it's just a solid pressed bronze powder piece of the same size and shape.

I don't think the fork is the problem.
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Old 02-10-2019, 07:38 AM
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Re: New build, clutch isn't releasing (83 z-bar woes)

Oh I did indeed replace it! Went with solid, not roller though. Used the bread trick haha

Good to know the throwout isn't in backwards or something!



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Old 02-10-2019, 06:08 PM
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Re: New build, clutch isn't releasing (83 z-bar woes)

The 82-83 fork is a 70-something fork.
They effectively tilted the trans. mount on the bell, re-bent-tubed a z-bar to work, and made existing parts work.
The previous effort on clearing the floorboards were a cable pull clutch fork (Vega or Monza).
And in between that was the 78-up A/G-body dogleg fork which has a bent-tube z-bar too; just less angle. The TO Brg. tube on that gets worn cockeyed; yours doesn't.
So it could be worse. If you keep the z-bar from breaking / wearing out, and use good rod-end bearing push-rod parts, it is a decent setup you have.

In the old GM stuff, there are 3 throwout bearing depths. The short version has the fork groove close enough to the bearing that it could not be moved half-inch towards the bearing. This is what was used in all V8 third gens.
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Old 02-11-2019, 08:08 AM
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Re: New build, clutch isn't releasing (83 z-bar woes)

jmd, thanks for the post! I just kept getting "swap to the hydraulic" as a reply on facebook groups.

So the fork is most likely correct, even though I can't find much for this part number? (5014090)

I can't find a non-stock photo of it to compare against the one every site says I should have (14037647 / 14550).

The bearing I used is the Centerforce N1716. I can't find any information about how long it is though. I wrote to Centerforce, I'll see what they say.

Thinking that has the be the problem, if the fork is indeed correct!
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Old 02-11-2019, 09:51 AM
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Re: New build, clutch isn't releasing (83 z-bar woes)

How much free play is there at the top of the clutch? I.e. with the pedal just sitting there, if you lift it, how far can you raise it?

If the TOB is too short, then there's often not adjustment available to adjust all the free play out; the clutch pedal sits too low; and of course the clutch won't release.

If the TOB is too long, there's not enough room between the clutch diaphragm and the front of the transmission; and the TOB can't retreat far enough from the diaphragm before it hits the trans, which holds the clutch partway released at all times such that it slips.

You don't seem to have the 2nd problem. Might have the 1st but probably not. If you do, you have the wrong clutch; it would be a "raised diaphragm" type, which is only used in low-torque (i.e. Honduh and 6-cyl type) applications. That does not appear to be the case at all: that type clutch would look like the "fingers" don't sit up as high as those in your photo. They would look more flat.

With the linkage, the force that should be working the clutch is actually applied between the motor and the body. Meaning, the linkage tries to wedge the motor and the firewall apart. if the motor moves on its mounts, or if the body (firewall mostly) flexes, it takes up motion that needs to be directed to the clutch instead. As little as " of this can render the clutch useless. This is one of the mainmost features that makes the hydraulic system so vastly superior to the old Ice Age linkage arrangement. Have your assistant sit in the car and push the pedal while you watch carefully to see if there is any of this sort of wasted motion going on. Watch the linkage as well, at the frame end; I've seen the frame fail there, allowing the part that the linkage is attached to, to bend.
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Old 02-11-2019, 03:17 PM
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Re: New build, clutch isn't releasing (83 z-bar woes)

Thanks for the informative reply sofa. When I got the email notification that you posted I assumed it'd say something like "Go hydraulic, I ditched that junk in the 80's along with my Marlboros and my mu||et" haha

I'll wait for the wife to get home and check pedal free play. From under the car, I can adjust the pushrod till there is no free play left in the z-bar at all with no change to the amount of clutch disengagement.

I received a reply from Jegs; the N1716 throwout is 1.254". They offer a 1.44" bearing by Hayes, P/N 490-70-104. They offered no advice on the situation, just the longer part.

I have solid motor mounts and a poly trans mount; shouldn't have any flex unless the firewall is. I'll inspect all mounting areas while she moves the pedal later on.

Any idea which throwout bearing length I -should- have?
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