# 68 GTO Z-BAR problem



## frankrp (Jan 19, 2015)

Don't know what happened here and no reason I should have payed more attention to a simple z-bar and clutch linkage that only goes in one way as I removed it but................ now that I am putting it back together with a new fork and clutch adjustment rod (which are identical to the old ones)and the pedal even with the brake pedal it puts the swivel(engine end of the Z-bar) angled forward instead of vertical so now the pushrod will not reach the fork. Adding a longer pushrod does not help. When the swivel is brought back (vertical) it turns the crank part of the z-bar all the way forward pulling the pedal down to the floor.It's almost as if someone cut the crank off and rewelded it back onto the bar at a different angle and if it looked like that was done I would just buy another but its never been touched as far as I can see. I repaired airliners for ten years with no problems and none of them ever crashed (that I know of) but I cant seem to get my clutch to work is there anyway I can blame Obama for this.


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## Matthew (Feb 11, 2011)

Frank, kind of hard to follow all of this. Did you replace the pressure plate and throw out bearing? If not, I suspect: 1)you might not have the TO bearing and fork assembled correctly, or 2) the wrong TO bearing, or 3) both. If you did replace the clutch, there maybe an issue with the new pressure plate. Of course, I might have scrambled what you are saying. Matt


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## Nightshade 68 HO (Mar 11, 2014)

Frank, Do you have an adjustable ball pivot on the bellhousing? I agree with Matt, I think the clutch fork and throw out bearing may not be adjusted properly. Is it the stock bell or a scattershield?


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## PontiacJim (Dec 29, 2012)

Again, a redundant statement. If you changed out the pressure plate and clutch with a new one, there are 2 different throwout bearings - a long and a short. Have purchased a clutch/pressure plate "kit" that comes with the throwout bearing only to find out the "kit" supplied the wrong one(I think the kit is really to fit a Chevy set-up which will work on a Pontiac EXCEPT for the throwout bearing). If you had the "short" throwout bearing, it would position the clutch fork at the throwout bearing closer towards the flywheel which would then cause the end where you put your clutch linkage rod to be much further away and you would think you needed a longer adjusting rod -this will not work as your geometry will be wrong and you will do damage. 

Don't know if this is what is happening, but it does sound like it if everything was working before the new parts and you have matched all your old parts against the new pieces (assume you purchased a clutch fork specific to Pontiac from one of the Pontiac resto parts suppliers and NOT the aftermarket one that "says" it will fit Pontiac and GM cars -it won't work, been there & done that). You have not told us if you installed a new clutch/pressure plate/throwout bearing -so I am guessing.


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## frankrp (Jan 19, 2015)

*reply to replies*

Thanks everyone for getting back to me I never actually drove this car on the road when I purchased it basically because it was a piece of junk only in and out of a garage as I intended on restoring it immediately,but I remember the clutch seemed to feel normal and pedal position ok .When I pulled the clutch out I could see it was pretty new along with a new flywheel and throw out bearing so I didn't change any of these components but the pivot was a little nicked up and the fork and push rod also So I purchased a new fork, pivot, and rod made in u.s.a. they all looked the same as the old ones.The bell housing is the same,the only thing I can think of is that I didn't compare the old and new forks well enough.I remember the ebay listing saying Fits:gto chevelle and a few other cars I' thinking about pulling out the fork to match it up to the old one again but I'm pretty sure it was identical. oh and the pivot is not adjustable it screws in with a large allen key and it was the same length as the old one.


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## PontiacJim (Dec 29, 2012)

frankrp said:


> Thanks everyone for getting back to me I never actually drove this car on the road when I purchased it basically because it was a piece of junk only in and out of a garage as I intended on restoring it immediately,but I remember the clutch seemed to feel normal and pedal position ok .When I pulled the clutch out I could see it was pretty new along with a new flywheel and throw out bearing so I didn't change any of these components but the pivot was a little nicked up and the fork and push rod also So I purchased a new fork, pivot, and rod made in u.s.a. they all looked the same as the old ones.The bell housing is the same,the only thing I can think of is that I didn't compare the old and new forks well enough.I remember the ebay listing saying Fits:gto chevelle and a few other cars I' thinking about pulling out the fork to match it up to the old one again but I'm pretty sure it was identical. oh and the pivot is not adjustable it screws in with a large allen key and it was the same length as the old one.



The clutch fork for the "fits gto, chevelle, and a few other cars" sounds like the first one I bought and had all my problems with -took out the clutch. Yes, quick glance looks like they are the same. Keep in mind its possible that someone already replaced it with the generic one and it would be identical. 

As I recall, where the throwout bearing rides on the fork (if you fit it together while outside the bell, will slip right past the fork fingers. This will allow the fork to do the same thing when its in the bell and on the pivot ball should it slip off the spring clip that holds it on the pivot ball. If that happens, you will bust that thin metal collar on the throwout bearing which the fork rides on -then you may find that chip going into your pressure plate/clutch and taking it out like mine did.

Again, you need to have the correct length throwout bearing.

The factory pivot ball is not adjustable. You can purchase an adjustable pivot ball that will replace the factory piece if needed. I put one in my car because I wanted a new one. As I recall, the ball end was slightly oversized in diameter where it fits into the clutch fork and I simply ground it down until it matched the factory pivot ball end diameter. 

And keep in mind that just because you have "new" parts does not mean you have the "right" parts. The previous owner may have purchased the wrong "fits gto, chevelle, and others" parts as it is easy enough to do when buying anything aftermarket. It happened to me and sometimes it is because of how the part is worded.:thumbsup:


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## frankrp (Jan 19, 2015)

*reply to last reply*

I don't think that is what happened but I will check it out this weekend anything is possible and I appreciate the help. The only other thing I noticed when I first bought the car was that even though the clutch grabbed where it should the pedal was extremely hard to press down when I took it all apart I could see someone put in a new flywheel and clutch and the disc pattern on one side looked like your average disc with the angled grooves all the way around but the other side has pucks then I thought someone had installed some kind of super heavy duty clutch with no markings other than (made in Korea),not that I think this is affecting the linkage geometry because as I said the pedal grabbed ok before I messed with it but I thought I would mention it and ask if you can recommend a clutch that wont kill my leg Thanks.


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## PontiacJim (Dec 29, 2012)

frankrp said:


> I don't think that is what happened but I will check it out this weekend anything is possible and I appreciate the help. The only other thing I noticed when I first bought the car was that even though the clutch grabbed where it should the pedal was extremely hard to press down when I took it all apart I could see someone put in a new flywheel and clutch and the disc pattern on one side looked like your average disc with the angled grooves all the way around but the other side has pucks then I thought someone had installed some kind of super heavy duty clutch with no markings other than (made in Korea),not that I think this is affecting the linkage geometry because as I said the pedal grabbed ok before I messed with it but I thought I would mention it and ask if you can recommend a clutch that wont kill my leg Thanks.



Check out the online *Ames* catalog which you can download. They have some good diagrams that might help as well as a detailed parts listing which may help to make sure you have the correct pieces. Here is a nice picture list of parts. 68-72 Pontiac Lemans-GTO Clutch Linkage

There are quite a number of clutch disc options out there, single & dual - organic, kevlar, carbon fiber, metallic, aluminum, mixed facings, typical flat facings, puck, puck on one side only, so it is hard to say who the maker is. How to choose a clutch material 

The heavy duty pressure plate is what gives you that hard pedal feel. Typically a diaphram pressure plate provides the "easiest" pedal effort, while the 3-finger Borg & Beck or Long have better holding power for higher HP & torque engines, but require a greater pedal effort. Clutch University Chapter 2 

It sounds to me like your combination is meant for higher horsepower and torque -which a built Pontiac will produce. Here is an overview of some manufacturers. Aftermarket Clutch Assemblies, Part Two | Hemmings Motor News

Many here on the forum like McCleod set-ups. Clutch Kits I had a Hays in my last 400CI build, but it was more at a typical stock HP level than something built for street/strip. Had no problems with it. Easy pedal effort. I used the carbon fiber disc with diaphram pressure plate. Now building a big 455CI with a lot of torque and went with the McLeod 12" diaphram pressure plate & matching disc per member ALKYGTO recommendations. Got mine through Summit to save on shipping. No comment on it because my car is still in parts.

AND FINALLY........read this thread as it may have some info/photos you can use that may be of some help.:thumbsup:
Pontiac Street Performance - Advanced Clutch Theory and Science


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## PontiacJim (Dec 29, 2012)

OK, here is an original 1968 Pontiac clutch fork out of my '68 Lemans. This one matches the new reproduction piece I got that was specific to Pontiac's, not the one that fits "gto, chevelle, and others." This may be of some help to you. Some measurements may seem off due to the angle of my camera when I took the shot, but I have the measurements listed as best I could see without pulling out a protractor or dial indicator.:thumbsup: Going to have to upload in a couple replies as I have 11 pics. Measurements include the dimensions between the pivot ball cup and adjustment rod cup. Probably the most critical is the height difference from the adjustment rod cup and the end of the fork measured at the level position at the adjustment rod cup. This will give you the correct curvature put on the factory clutch fork so it pivots correctly on the pivot ball as fitted to the adjustment rod coming off the Z-bar and the relationship between the throwout bearing & pressure plate distance.

Photo #1-11" overall length, #2-7" distance from cup to cup, #3-just under 3 1/2" from cup to fork end, #4-3 1/2" wide, #5-1 1/2" from inside curve to end of fork.


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## PontiacJim (Dec 29, 2012)

Picture #6-1 5/8" wide, #7-side view showing arch, #8 about 1" at the highest point contour-pivot ball end, #9-7/8" as it steps down going to the adj. rod end cup, #10-2 1/2" as measured with the adj rod cup end made level off the top flat area of the cup while on the table.


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## PontiacJim (Dec 29, 2012)

Picture #11-1 1/4" high at the fork end that holds the throwout bearing. Fork is still positioned in the level position as measured at the adj rod end cup. If the repro clutch fork does not measure the same at these 2 points while the adj rod cup end is made level, this will impact the fulcrum effect needed to operate the throwout bearing in and out. Measurements between the pivot ball cup and adj rod cup will also impact throwout movement.

So use these measurements to get an idea as to whether or not your repro clutch fork is similar or different. If it matches up, then you have other problems somewhere and we can go from there.:yesnod:


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## PontiacJim (Dec 29, 2012)

Dug up 2 Pontiac throwout bearings that are used depending on the pressure plate style. One is the "long" type and one is the "short" type. Some pressure plates have the diaphram fingers laid flat while others have them raised up. As I recall, the flat finger type would need the "long" while the raised fingers use the "short." One bearing has a larger surface, but this is more due to manufacturer.

If you used the "short" throwout bearing on a flat finger diaphram, it would move the end of the clutch fork that goes onto the throwout bearing closer to engine/flywheel side and pivot the end which sticks out of the bellhousing further back towards the back of the car. This would increase the distance from the adjusting rod cup to the actual adjusting rod itself. You would think that you could adjust the rod all the way out, but this usually isn't enough AND the geometry of everything will be off. The clutch fork at the throwout side will be at too steep an angle and you may break off the throwout bearing, plus you will not get the needed leverage you want and this may explain your hard pedal.

The part of the clutch fork that sticks out of the bellhousing should be angled forward while the portion still inside the bellhousing should be somewhat parallel with the pressure plate.

The "long" or "short" throwout bearing has to be matched with the pressure plate. I also think there is another one at a different length as well and I think it may be even longer. Whatever size you need, the arm of the clutch fork should be in a forward angle to meet up with your factory clutch adjustment rod. An adjustable pivot ball could be used to fine tune the clearance/air gap needed between the pressure plate and throwout bearing face. You do not want the throwout bearing setting on the pressure plate fingers. Many clutch manufactures have a recommended air gap between the clutch and the flywheel while you push the clutch in to the floor. Takes 2 people and a feeler gauge. I never do this. I adjust the clutch to get a clean release and have it engage about mid-way or a little less of the total clutch pedal travel - I don't like it grabbing off the floor or too high.:thumbsup:


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## frankrp (Jan 19, 2015)

*reply to jim*

Wow I never expected so much info. So today I removed the recently purchased fork from ebay (which I noticed had a GM# on it) and matched it up to the old one which is exactly the same as yours ( the geometry was slightly different between my old and new) I then installed the original back and had the same problem.As a last resort I cut off the crank from the z-bar and welded it back at a more vertical position maybe 80 degrees instead of 65 degrees . Now pedal position,travel,and foot pressure is excellent and no interference with the headers. A bit of a Rube Goldberg but it works.


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## PontiacJim (Dec 29, 2012)

frankrp said:


> Wow I never expected so much info. So today I removed the recently purchased fork from ebay (which I noticed had a GM# on it) and matched it up to the old one which is exactly the same as yours ( the geometry was slightly different between my old and new) I then installed the original back and had the same problem.As a last resort I cut off the crank from the z-bar and welded it back at a more vertical position maybe 80 degrees instead of 65 degrees . Now pedal position,travel,and foot pressure is excellent and no interference with the headers. A bit of a Rube Goldberg but it works.



Sounds like a winner. Have had my share of clutch problems and resolves along the way, so wanted to throw everything at you and pictures are worth a thousand words in trying to get across what you want through emails.

I guess it is possible that your Z-bar was simply manufactured wrong. Have had these experiences as well with aftermarket items that are "supposed to" work or fit and simply don't or need to be modified. So now you are on your way to getting the car that much closer to the road.:thumbsup:


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