280zx trans in 240z - Which clutch M/C and slave?

[inline6]

I tend to be rather wordy, so I am editing and putting the questions up front:

1. With a 240 mm clutch upgrade and a late style ZX gearbox, are the stock clutch master cylinder and stock slave cylinder suitable to achieve enough travel for full disengagement of the clutch disc, without pre-loading the throw out bearing?  
2. If so, can suitable travel be achieved with the clutch pedal in the stock position - 8" from the floor?
3. If not, has anyone focused on this issue and come up with a combination of MC and Slave that does work with the clutch pedal at 8"?

(End edit)

 

I've never been happy with my clutch since I switched to a late style 280ZX 5 speed eons ago. I messed with pedal height and got it to work ok way back then and drove it for years without any real issues.  However, with my new engine which revs higher, I am having a much harder time getting it out of gear and getting it into gear at high revs.  

 

Today, I tried setting the clutch pedal height back to stock per the FSM.  I set it at 8 inches from the carpet on the floor to the front surface of the rubber foot pad by undoing the lock not on threaded M/C rod and screwing the rod into the clevis more to lower the pedal height.  After doing this, I can no longer get the car to shift into gear with the engine running.  Clearly the clutch pressure plate spring fingers are not being engaged enough to release the clutch disc.  

 

The clutch M/C and slave have been checked for leakage and there is none.  System has been bled thoroughly and no air bubbles are coming out.  I have visually verified that the rod on the slave is moving the clutch fork.  Additionally, I took the slave off the tranny, took out the clutch fork boot, and shined a light up inside the tranny.  I tried moving the fork by hand back and forth.  In it's natural static position, it seems to me that the throw-out bearing is resting on the pressure plate spring fingers.  I can't force the fork (pushing toward back of car) and achieve any movement at all.  I can, by putting light force from the back toward the front, get the fork to move some in that direction.  That obviously pulls the throw-out bearing/collar away from the pressure plate.

 

My clutch master cylinder is a 5/8 Nabco.  It is stock 240z as far as I can tell.  My slave cylinder is 3/4" Nabco.  Are these suitable, or no?

 

The disc and PP have about 1500 miles on them.  They are ClutchMasters 240mm units which are mounted on a Fidanza aluminum flywheel.  

 

Through my searching I am aware that there are different T/O bearing collars and that I need to have a stacked height of 92 mm from the flywheel surface to the "wings" on the throw-out collar that the clutch fork rubs against.   

 

Is there any way to measure this without take the trans out of the car?  

 

Clearly, something isn't optimal.  If I raise the clutch pedal about another inch or so higher than the brake pedal by screwing the threaded rod in the clutch M/C out, I can get a functional clutch. As I said before, however, 7000 rpm shifts pretty much don't work - the shift lever resists my efforts to pull out of first... and I can't get into second until the revs drop below 6000.  Also, the reverse idler gear is not quite stopped... it is causing a bit of grinding when shifting into reverse even with the clutch pedal firmly against the pedal stop.

Edited July 5, 2015 by inline6

[NewZed]

 

 

Is there any way to measure this without take the trans out of the car?  

 

 

The location of the fork in the hole, front to back, should correlate to the angle of the fork on the pivot ball which should be affected by the stack height of TO collar and pressure plate.  You could measure from the front of the fork to the hole edge and see if anyone out here could do the same.  You'll have to dink around with the rubber dust boot but it sounds like it might be removed already anyway.

[inline6]

I just verified that stock 1983 Datsun 280ZX non-turbo has a 5/8" clutch master and 3/4" slave... same as what I have now.

 

Just found this post (#8 in thread) from Tony where he points out that there is a common problem with clutch master cylinders that have rods that are too short.  He mentions aftermarket...  I don't think mine is aftermarket because it is a Nabco, so maybe it isn't just an aftermarket issue.  

 

His post #9 is also interesting... I have been wondering why my poor shifting seemed to have gotten worse recently when it had been workable for many years.  The new clutch disc actually makes the problem worse because the fingers in the spring diaphragm actually move away from the throw out bearing a bit more.  As a clutch disc wears the finger move closer to the T/O bearing.

 

And finally, in that post, the original poster (OP) states that they solved their problem with a slave from a 1988 Pathfinder.  

 

I looked around for some images and see that the Luk one at RockAuto has numbers on the side like the original equipment (OE) ones.  It looks to me like it says 11/16. Ok, now I see some of the descriptions of the others say 11/16".  Same amount of volume of fluid being forced (MC) into a smaller container (slave) would cause the slave piston to move further... and man are those Pathfinder slaves cheap!

Edited May 17, 2015 by inline6

[inline6]

Found another zcar.com thread with info about clutch pedal height that is interesting - Tony again... go figure.  The FSM says to use the threaded rod on the clutch master cylinder to set the clutch pedal to the correct height off the floor.  But Tony says (in post #10):

 

"Pedal height is pretty much irrespective of the adjustment---the bumper on the screw should adjust that...the clevis simply sets where the piston is within the cylinder itself."

 

Now, that is interesting.  As I stated above, I set the clutch pedal height at 8" by threading the clutch master cyl. threaded rod in until the pedal was 8" off the floor.  I then set the rubber bumper on the screw so it was snug against the clutch pedal arm.  Setting it in this fashion made it so I could not shift into any gear with the engine on.

 

Separately, when I bolted the slave cyl. to the transmission, I had to compress the slave cyl. rod.  Fully compressed, the slave will bolt to the tranny with no issues.  The piston in the slave is pretty well bottomed out.   

 

Based on what Tony said, I decided to test something. 

 

I loosened the lock nut on the rubber stopper and backed it as far away from the pedal as possible.  Then I loosened the lock nut on the clutch master cyl. rod and screwed that rod out of the clevis until the pedal was again in the position where the clutch became functional.  My clutch pedal is now at like more than 9 inches off the floor - more than an inch higher than the brake pedal.  Then... I again set the rubber bumper to hold the clutch pedal at 8" off the floor.  But, as I did so I watched the slave cylinder.  And, as I moved the clutch pedal down from 9+ inches to 8", I saw that the slave cylinder rod moved, which "pre-loaded" the throw out bearing on the PP spring fingers.

 

So... given what Tony said: "Pedal height is pretty much irrespective of the adjustment---the bumper on the screw should adjust that...the clevis simply sets where the piston is within the cylinder itself", and what I see happening on my car from the aforementioned steps that I took, then what gives?  

 

My conclusion is that the only way he could be right is if one additional thing is done in my scenario with my car.  If it is true that pedal height can be irrespective of the adjustment... that I can set that simply with the rubber bumper on the screw... then the only way to alleviate the slave cylinder movement I am experiencing is if I crack open the bleed circuit after I have set the clutch for proper operation with the clutch master cylinder threaded rod. But won't that just return the slave rod back to the original start position and won't I lose all of that travel (that I had)?

 

I'll give it a shot, but seriously, I am coming to the conclusion that the 5/8" MC and 3/4" slave don't have the stroke to get this job done.

 

 

[RebekahsZ]

I set my pedal so that it works properly. After that, I adjust for minimum wasted travel. Then, if that's all good, I try to set the clutch and the brake to the same level. But, brake gets set to allow good heel-toe with the go pedal. Get it working properly to start with. Oh yeah, the hell with what any book says on this subject. Unless you are on classiczcar.com.

Edited May 19, 2015 by RebekahsZ

[duragg]

Hehe...

I found if I heavily preload my T/O bearing I get more disengagement of the clutch and silent shifting even in "combat" at 8000 rpm. Since I tend to blow my car up a lot I just figured I'd replace the bearing frequently (but it seems unfazed so far).

 

I just purchased a Wilwood 7/8 (Wil-260-3376) which should give enough throw power and adjustability but haven't installed yet as car just got re-repainted. Hopefully it doesn't shoot the slave out the back of the garage lol

 

http://www.zdriver.com/forums/240z-280zxt-s30-s130-tech-tips-275/clutch-master-swap-upgrade-31422/

 

Further: I ordered a Strange Engneering 1.125 brake master because the Wilwood 1" I was using still had too much pedal travel for my taste.

 

I will try to remember to post an update.

Edited May 19, 2015 by duragg

[erikr]

In 2011 I called Exedy and asked them how much t/o bearing travel is needed to disengage a clutch.

Their response was It should start to disengage at approximately 6 mm of t/o bearing travel, at 8mm most clutches will be completely disengaged, these are generic numbers the lever ratio of the pressure plate spring will have an effect on these numbers.

My old t/o bearing fork has a ratio of ~1.9 to1, so 8x1.9=15.2mm needed at the slave cylinder. I measured my slave cylinder travel tonight at 13mm.

I have the non-adjustable slave cylinder set up, the t/o bearing is always touching the fingers of the pressure plate so all 13mm are used to depress the pressure plate. I am shifting around 6400 and the clutch is disengaging. I have a 240mm Jim Wolf technology clutch and a Fidanza flywheel. Hope this helps.

[inline6]

Hehe...

I found if I heavily preload my T/O bearing I get more disengagement of the clutch and silent shifting even in "combat" at 8000 rpm. Since I tend to blow my car up a lot I just figured I'd replace the bearing frequently (but it seems unfazed so far).

 

But, doesn't pre-loading of the T/O mean the pressure plate spring fingers are loaded also?  And so the PP isn't clamping with full available force?  I can see how that would still work, but one really doesn't know how much slippage is occurring, right?  A suitable compromise... sure, but I would prefer to have properly engineered/functioning parts.

 

I'm curious how much of your "solve" of high rpm shifts is your mods. vs. more travel, by the way.  If I get enough travel, I may find out.

[Six_Shooter]

This might get a bit wordy as well...

 

So my '73 was original automatic, unimportant, but part of the story. I swapped in a 4 speed initially with a 225mm centerforce DF clutch. I used stock master and slave, 5/8" master, 3/4" slave. This worked well for a few years, even after turbocharging the engine and would shift regularly above 6000 RPM. I noticed a bit of an issue if I really tried to rev the engine much higher trying to get the clutch to disengage. It would work, but never felt as smooth as I would have liked. 

Over the last couple of years I found that the clutch disengagement just didn't seem as good as it once was. The slave might have been failing.

Well, move up to last summer, when I swapped in a different drive line consisting of a GM 3.5L V6 mated to a 1992 Z32 transmission. (required a custom adapter, might be an important detail). I was able to keep the Centerforce DF clutch that I had been using for a few years with the turbo L28 (Thanks Nissan for keeping input splines the same ). Once I swapped the new driveline in, I was left with a little bit more play in the clutch arm travel than I liked, but I figured I'd give it a try as it was, since no one had done a swap like this before me,so there really was no reference for what might or might not have worked here. Note: the Z32 throwout bearing will fit on the S30 clutch sleeve, but is a bit thicker, which might help someone. It was my back up plan if the clutch didn't work out well. It is larger in diameter, so it may have trouble fitting with some pressure plates. 

I would occasionally not be able to shift into gear at a stop (would take several pumps to get it to go), and pretty much forget shifting in anger. This indicated a hydraulic problem, but could never find a leak, flex hose looks good and the fluid was always up.
 

Fast forward to this spring when I finally got fed up with the situation, threw the car on the hoist and checked everything. ZERO leaks, it even seemed to work right on teh hoist. Well I had other clutch hydraulic parts that I got out of parts cars or from friends, so I decided to swap both the master and slave. Out of the two spare masters I had, only one was good, so I swapped it on. I then noticed that one of the slaves I had was an 11/16 version, and thought about it for a few minutes and decided to try it because if I had my hydraulic thinking correct, this would give me a bit more throw, with a slightly higher pedal effort.

After some difficulty getting it to bleed, I decided to swap the original master back on, no change in bleeding, and finally after way too long found that the bleeder hole in the body of the slave (not the bleeder nut itself), was plugged with something. Once that was cleaned out, it bled as one would expect. (I spent way too long finding that problem :/ )

The result?

I can now shift in anger, or joy, or any other mood at any RPM I want without issue.

So I give a thumbs up for trying that 11/16th master, it might be just what you need, especially if you have an after market clutch that might require a little more throw to function properly. Just make sure you don't get too much throw, that could damage the pressure plate. I don't know where mine came from, so I can't say if the Pathfinder one would be the same, but it should work, seeing as the transmissions are the same as the one I have in my car (FS5R30A), and I had both the stock S30 slave bolted onto the trans and this 11/16th version.

BTW, the Z32 clutch fork is the same shape as the S30/S130 uses, but is made from a thicker material, so you might also want to look into using one if you feel that the clutch fork is flexing.

Edited May 21, 2015 by Six_Shooter

[duragg]

Yes the fingers were preloaded but its a pretty heavy duty clutch and I don't make all that much power on a NA 3.0L only operating at high RPM and it had Zero slippage (its sitting on the floor for other reasons as we speak).

 

As for my other "mods" success vs just more clutch travel... I prefer to think I alone saved the earth from crunching shifts so nanny-nanny I can't hear you.

 

I have the new 7/8 Wilwood master installed but I have to use the longer Wilwood rod and cut it down and find a new clevis and all that seems to take days instead of minutes.    As mentioned previously if it is too  much fluid and the slave falls out I will just have to find a way to limit travel.  I also think its going to be a pretty stiff pedal push, but during a race that isn't something one notices.

 

TJ

[inline6]

So I give a thumbs up for trying that 11/16th master, it might be just what you need, especially if you have an after market clutch that might require a little more throw to function properly. Just make sure you don't get too much throw, that could damage the pressure plate. I don't know where mine came from, so I can't say if the Pathfinder one would be the same, but it should work, seeing as the transmissions are the same as the one I have in my car (FS5R30A), and I had both the stock S30 slave bolted onto the trans and this 11/16th version.

BTW, the Z32 clutch fork is the same shape as the S30/S130 uses, but is made from a thicker material, so you might also want to look into using one if you feel that the clutch fork is flexing.

 

Nice.  Plus one for buying a $9 dollar 11/16ths slave and giving it a shot.

 

I have the new 7/8 Wilwood master installed but I have to use the longer Wilwood rod and cut it down and find a new clevis and all that seems to take days instead of minutes.    As mentioned previously if it is too  much fluid and the slave falls out I will just have to find a way to limit travel.  I also think its going to be a pretty stiff pedal push, but during a race that isn't something one notices.

 

TJ

 

Regarding the clevis, I read where one person modified theirs just by drilling the threaded hole out of the clevis they had and welding a nut with thread that matches the rod to it.  If you have a welder, that may expedite your project.  A lock nut is still needed, of course.

 

7/8" is "a lot" bigger than 5/8" when it comes to these master cylinders, isn't it?  My car is already beastly to drive in so many ways after various mods... adding another by switching to a heavy clutch pedal doesn't appeal to me. 

[duragg]

^ yes that idea of adding a second nut came to me in the middle of the night as well and I will probably do that.

I have a pretty heavy clutch too, but I have never noticed it as being a fatigue item in a race.

About to find out I guess.

 

Next solution would be to take my spare clutch pedal and move the hole up maybe .25" to .500" to improve feel?
 

[inline6]

Did some measuring today.  I backed the rubber bump stop away from the clutch arm completely.  I set the clutch m/c rod so that the clutch engagement off the floor felt right - not too high off the floor, not to low.  My clutch pedal was roughly 1.5 to 2 inches higher than the brake pedal which is at FSM height. 

 

I then set the clutch pedal so it was hard against the clutch pedal stop on the floor.  Then I measured the clutch fork distance from the slave.  After writing that number down, I released the clutch pedal completely and measured the the clutch fork distance from the slave again.  I calculate that I have 21.8 mm of total throw at the slave right now, but... I then set the rubber bump stop against the clutch arm to bring the clutch pedal to approximately the same height as the brake pedal.  And I took another measurement at the slave.

 

With the clutch pedal height reduced, I now have 15.2 mm of travel at the slave.  That means the slave has been activated by 6.6 mm... with the clutch pedal now in the new static position.

 

I drove the car, and shifts are not bad.  I also don't notice any clutch slipping.  But with 6.6 mm of travel already occurring (this is net of any slop in the clutch pedal linkage by the way) the t/o bearing is clearly "running" at all times, and the pressure plate spring fingers are somewhat depressed.

 

This is not right enough for me...

Edited May 31, 2015 by inline6

[NewZed]

The hydraulic is self-adjusting, resetting "zero" start point each time the pedal comes up.  With the pedal up you can push the slave rod back in to the cylinder by hand, pushing fluid back in to the reservoir.  Your adjustments at the pedal would preload a mechanical system though.

 

So you didn't have 6.6 mm of activation at the start, you lost 6.6 mm on the other end, after your pedal adjustment.  I assumed (or maybe saw somewhere, can't find it) that Duragg used a mechanical means to preload his clutch.  You'd have to have the slave bottomed out and an adjustable rod at the slave and extend it out to preload the fingers.

 

 

Forgot to say that if you do push the master cylinder rod too far out and piston too far in that you can block the return hole and lock the hydraulics.  Then when they heat up they'll push out a little farther.  Uncontrolled.  It happens in brake cylinders.

 

 

I've always felt that my clutch is kind of inconsistent in engagement point and wondered if it was the hydraulics.  Considering how the seals can blow I'd think that somebody would have designed a mechanical system, for racing or just general simplification.  You could probably design a cable pull.

Edited May 31, 2015 by NewZed

[inline6]

The hydraulic is self-adjusting, resetting "zero" start point each time the pedal comes up.  With the pedal up you can push the slave rod back in to the cylinder by hand, pushing fluid back in to the reservoir.  Your adjustments at the pedal would preload a mechanical system though.

 

The spring diaphragm mechanism on the pressure plate pushes everything (the t/o bearing, sleeve, fork, and clutch slave piston) back.  It all settles... with the c/s piston in a position which is pretty well bottomed out in the slave.  I confirmed this by removing the two bolts that mount the slave and trying to compress the piston more.  It doesn't go very much further at all... maybe a 1/16th of an inch.  

 

Right now, on my car, the piston on the slave is "out" enough that of its total 21.8 mm of travel (again, with the way everything is set in my car right now), 6.6 mm of it is gone.  So the remaining 15.2 is available.  

 

If I were to crack open the bleeder on the slave, then the piston in the slave would again retract fully.  And given everything else in my clutch system is not changed, once I tighten the bleed screw again, I'd have a not functioning clutch because I'd only have 15.2 mm of travel available.  In order to get more, I'd have to back of the little bump stop that holds the pedal at ~ the same height as the brake pedal again.  

 

That would retract the piston in the clutch m/c so that once pushed forward again, I could again pick up the 6.6 mm that was lost when the bleeder screw at the slave got opened.  I could again set the clutch pedal height using the little rubber bumper pad, but I'd be right back where I am as the car sits - 6.6 mm of a total of 21.8 mm of stroke having occurred at the slave already.

 

So you didn't have 6.6 mm of activation at the start, you lost 6.6 mm on the other end, after your pedal adjustment.  I assumed (or maybe saw somewhere, can't find it) that Duragg used a mechanical means to preload his clutch.  You'd have to have the slave bottomed out and an adjustable rod at the slave and extend it out to preload the fingers.

 

I don't think he is using mechanical means.  If you push in the clutch pedal somewhat, so that the slave is engaged and moves the clutch fork, and you then lock the position (with the little rubber pad that contacts the pedal), you've pre-loaded the clutch... with a hydraulic system.

Edited July 5, 2015 by inline6

[NewZed]

 

If I were to crack open the bleeder on the slave, then the piston in the slave would again retract fully.  And given everything else in my clutch system is not changed, once I tighten the bleed screw again, I'd have a not functioning clutch because I'd only have 15.2 mm of travel available.  In order to get more, I'd have to back of the little bump stop that holds the pedal at ~ the same height as the brake pedal again.  

Interesting stuff, but outside the design principles.  The system is under pressure all of the time that way, and the clutch will move toward disengagement as the fluid heats and expands, and away as it cools.  Could also be susceptible to losing adjustment over time if one of the seals leaks slightly.  Actually, I think that my moving disengagement point is probably due to slight leakage of the primary seal in the MC.  Internal slippage.

 

Also, your method makes the fluid in the reservoir irrelevant.  It never gets in to the line or the slave.  Probably stays nice and clean though.

 

Anyway, sounds like you know what's happening.  I'd use a bottomed out slave piston and adjustable slave cylinder rod if I wanted to have the TO bearing pressing on the clutch fingers.  It lets the hydraulics do their intended thing and would be more stable in use and over time.  Easier to adjust also, and allows maximum throw from the pedal.

[inline6]

Interesting stuff, but outside the design principles.  The system is under pressure all of the time that way, and the clutch will move toward disengagement as the fluid heats and expands, and away as it cools.  Could also be susceptible to losing adjustment over time if one of the seals leaks slightly.  Actually, I think that my moving disengagement point is probably due to slight leakage of the primary seal in the MC.  Internal slippage.

 

Also, your method makes the fluid in the reservoir irrelevant.  It never gets in to the line or the slave.  Probably stays nice and clean though.

 

Anyway, sounds like you know what's happening.  I'd use a bottomed out slave piston and adjustable slave cylinder rod if I wanted to have the TO bearing pressing on the clutch fingers.  It lets the hydraulics do their intended thing and would be more stable in use and over time.  Easier to adjust also, and allows maximum throw from the pedal.

 

To be clear, I don't like the situation.  I'm just describing it.  I'd like to come up with a solution so there is enough fluid being passed to give the slave the travel that needs to occur for full clutch disc disengagement... with stock clutch pedal stroke.  

 

There is always this option - lol 

[Six_Shooter]

Have you tried that 11/16" slave yet? That solved my clutch disengagement issues.

 

K.I.S.S....

 

Don't over think it, you'll do more work than you need for same or worse result.

[inline6]

Have you tried that 11/16" slave yet? That solved my clutch disengagement issues.

 

K.I.S.S....

 

Don't over think it, you'll do more work than you need for same or worse result.

 

I started to order it from RockAuto, but decided shipping and handling or whatever was a bit much for the one part.  Am going to find a couple of other items I need and get it coming.  

 

Also had the thought to do some measuring.  I mean, I can measure how much M/C rod moves for each inch of pedal movement, and the same for the slave.  I should be able to take the FSM clutch pedal stroke (8" from floor to clutch pedal stop) and knowing the diameters of the stock M/C and slave, calculate volume displacement for each.  Then, I might be able to figure out what size m/c and slave would be required to work with that same stroke to get full disengagement.  

[inline6]

I finally got around to ordering the pathfinder slave cylinder and got it installed tonight.  Here is some info while it is fresh in my mind:

 

I don't recommend the pathfinder slave for a couple of reasons.  First, the casting is such that the flat part of the mounting ears that seat against the transmission are not in the same place as the OE 280ZX one.  The cylinder part of the casting hits the tranny casing well before the ears contact.  You have to install a stack of about 1/4" of washers (or even more) under the mounting ears in order to mount it.  I used three thick washers per ear.  

 

Next, the bleed screw and the hydraulic fluid supply hole in the slave for the hose are reversed from the OE slave.  When mounted, the hose is the highest point and the bleed screw is down low.  It still bleeds, but switching positions for these is not desirable.  

 

I did some travel measurements, but they are not all in front of me and I'm not going to go ffind them all right now.  What I recall:

 

With the OE slave cylinder unbolted and away from the transmission, I put a piece of pipe over the end of the fork to use as a lever arm and manually operated the clutch fork while taking a travel measurement.  I measured from the front edge of the slave cylinder boot to the front edge of the fork.  I measured pretty much right on 5/8th's of an inch from rest position to "that is all I can get with this piece of pipe" position.  I did this about 4 times putting a fair amount of force on the pipe to try to get more travel and couldn't.  The pressure plate springs seemed to be bottoming out and not allowing more travel. 

 

After installing the 11/16th's Pathfinder slave with the stacks of washers and bleeding it, I took more travel measurements.  At rest, the distance from the front edge of the slave boot to the front edge of the fork was 1.140".  The hydraulic system was bled and locked down with the clutch pedal bump stop screwed all the way in (so as to be as far from the pedal arm as possible - it was not touching the arm in this position).  The clutch pedal rubber pedal pad surface was nearly 2" above the brake pedal pad surface. My brake pedal height is as factory shop manual (FSM) height. I then used my handy dandy "the club" steering wheel lock wedged between the seat and the clutch pedal to hold the pedal tight against the bottom factory rubber stop, which the pedal hits when fulled depressed.  I took another measurement.  I don't recall this measurement exactly at the moment, but it was something like 1.9" which kind of freaked me out -- I gotta say.  Because that is like over an 1/8th inch more travel than I got using the piece of pipe.  I wonder if the pressure plate springs were bottomed out and were bending, yielding to the extra travel!  I dunno...

 

But, assuming that was too much travel, I went back to the idea of setting the clutch pedal to the same height at the brake pedal - this reduces the amount of travel at the clutch master cylinder.  

 

First, I set the clutch pedal at the same height as the brake pedal.  I locked the lock nut on the rubber pedal stop.  I then hooked up my bleeder hose and released the pressure in the system.  This set the piston in the slave back to "full rest" or the "fully retracted" position.  i confirmed that the fork was not under load, that the slave was not pushing against it.  The fork moved a smidgen when wiggled back and forth by hand.  

 

I then used "the club" again and measured travel at the slave as I had done before.  I got something just less than 5/8th's - i can't remember exactly.  So, I loosened the lock nut on the rubber pedal stop and turned it in two complete turns so that it backed a bit away from clutch pedal arm.  That caused an increase in the travel at the clutch master cylinder by a very small amount. 

 

I found that setting the clutch pedal just a touch higher than the brake pedal (about an 1/8th of an inch) got me really close to the .625" of travel that I saw when using the pipe.  Assuming my 5/8th's total measurement is close to accurate for actual full travel on my pressure plate...  combined with my current pedal height, and my current clutch master cylinder rod setting, this set-up  "should be" providing me with full pressure plate spring disengagement. 

 

It's too late tonight for a test drive.  I'll check it out this weekend.

 

Regardless, even if this work's it's not a good enough solution for me.  I don't want this particular slave cylinder.  I'd like to find one that fits better; without washer/spacers and with the bleed screw and the hose in the proper locations.

 

Second, this has me thinking about potential differences in the 280ZX and the 240Z (mine is a series I) clutch pedal assemblies. My clutch MC, and the slave that were in the car are correct, 280ZX units - 5/8th's and 3/4" respectively.  Setting my clutch pedal at the 240Z FSM height off the floor... doesn't work at all.  The clutch is non-functional - I can't select any gears with the engine running.  Perhaps my aftermarket performance pressure plate (ClutchMasters) is part of the problem.  But, I am thinking the problem is actually a difference in clutch pedal travel from one car to the other.  I think the stock 280ZX clutch pedal travel is substantially greater than the stock 240Z clutch pedal travel.  This seems much more likely to be the issue to me.  Maybe that is the "problem" everyone who has a 240Z has been fighting when they swap out to the 280ZX tranny, and can't get the clutch to adjust correctly.  I have a 280ZX FSM.  So, I'll take a look at that when I have some time.

Edited July 10, 2015 by inline6