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Rcv — 150.    Mine - 153

               73.                  74

               20.                  18

               25.                   26

as well, I get 136 to the flat that the pivot screws into, Hope this helps.

Edited by 240dkw
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On 7/20/2020 at 6:43 PM, 240dkw said:

I get 136 to the flat that the pivot screws into

I just pulled off my transmission again to measure this, and I get the same as you - ~135mm to the flat. I remeasured the distance from the transmission face to the pivot, and I now get 105mm with my extra 4mm of washers.  I must have made a measuring mistake the first time.  I’m uploading my amended drawing below. 
 

 

C7388C12-CD93-45DF-B10D-3634BE8A4613.jpeg

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Yeah, I agree. I can't really wrap my head around our disparities in measurements.  We seem to get the distance to the pivot mounting flat, and our pivots seem to be the same dimensions. However, we get different measurements from the bellhousing face to the pivot even when I take my extra washers into account.  You don't happen to have the original pressure plate that came with the car do you?  My theory is that the one that goes with the 71A transmission is actually taller than the one that goes with the 71B.  

 

I'm getting pretty close to putting this into the cold case files anyway. I did take some 3d scans of the inside of the bellhousing just in case I want to reference it later.  You can check out a preview here:  https://platform.standardcyborg.com/sharescan/igyMyZc7.  I took a couple that I'll align and mesh together at some point, but just let me know if anyone wants the raw data.

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  • 1 month later...

Just a quick update for anyone else who runs across this: 

The engine/transmission is now in the car, and even though it's not running yet I did some test runs by pushing my car down my driveway, putting it into gear and then slowly releasing the clutch.  Things feel pretty good, so I'm going to call this a success so far.  I'll post a final update once the car is driving.

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  • 5 months later...
On 7/3/2020 at 6:42 PM, rcv said:

8C928842-E560-4749-8CD6-AA370BCCFA55.jpegYeah looks like I read closer to 150mm. Possibly this pressure plate isn’t right for my setup? I could have sworn I checked the height and it was the same as the old one. I’ll pull the transmission off and check again. 

I’m really hoping I don’t need to get another pressure plate as I already had this one balanced with my flywheel. 
 

 

I seem to have exactly the same issue

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I read the full 5 page thread. It seems to me the clutch kits from zsource may be the culprit issue. Too late and messed up for a return. Any idea where is can source the correct clutch assembly to use original gear/sleeve? Ild be satisfied to pay the additional cost to buy another as long as it works.

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“Someone” totally has to design a variable length throwout bearing collar. Then buy any clutch you like and adjust the length of the collar to get the “rule of 92mm” total height. Enough of these struggles already.

 

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One thing that I had forgotten about that I've seen on other cars, is the height of the pivot ball.  We really should have that pivot ball height as a variable in the whole "92 mm" solution.  If the pivot ball is short that screws up the whole equation.  The washer under the pivot would be a factor too.  I seem to recall a lock washer.

Here are are some examples.  I wonder if there are variations in the Nissan transmissions.

https://www.speedwaymotors.com/Adjustable-GM-Bellhousing-Clutch-Fork-Pivot,712.html?sku=5503855&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=CjwKCAiAm-2BBhANEiwAe7eyFG8N4a_JIC8cKxYJpinHOb48MAHr5-x6wb0xJJmKFLVknBKHIUyi_hoCgNgQAvD_BwE

https://www.jegs.com/i/Hays/490/84-116/10002/-1?gclid=CjwKCAiAm-2BBhANEiwAe7eyFNypj6L5trSXEoFY_4KFgt8v37pZIJ7MPtWAlID2eYNIsuk80E8oExoCaGMQAvD_BwE

Edited by Zed Head
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Part #7 shows two numbers, but the first is probably the monkey-motion transmission.

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/clutch

And the lock washer, #8.

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/clutch/8

Edited by Zed Head
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Posted (edited)
19 hours ago, Sailor Bob said:

I read the full 5 page thread. It seems to me the clutch kits from zsource may be the culprit issue.

Sorry to hear you're having the same problem @Sailor Bob, but at least neither one of us is crazy (or we both are).  I had to re-read the thread to remember, but it seems to me like the issue isn't actually the pressure plate or the collar, as I was getting the proper 92mm stackup.  The problem seemed to be that that my pivot ball was too short.  I'm not sure how it's possible, as @240dkw's pivot measures the same on the bench as mine but a few mm longer when installed.  Some kind of local space-time distortion is the best I can figure (or measurement error on my part, whichever makes more sense).

 

Adding an extra 4mm of washers under that pivot ball brought the distance from the tip of the ball to the front face of my bellhousing to 105mm (@240dkw's measured 103mm).  The transmission is now installed and I've been driving the car every chance I get. The clutch feels perfect.  I'm hopeful you can solve the mystery, but if you get tired I recommend just slapping two 2mm washers under that pivot and see if that fixes it for you.

Edited by rcv
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8 minutes ago, rcv said:

Adding an extra 4mm of washers under that pivot ball brought the distance from the tip of the ball to the front face of my bellhousing to 105mm (@240dkw's measured 103mm).  The transmission is now installed and I've been driving the car every chance I get. The clutch feels perfect.  I'm hopeful you can solve the mystery, but if you get tired I recommend just slapping two 2mm washers under that pivot and see if that fixes it for you.

Thanks for the reminder, I had forgotten how you solved the problem (state-dependent memory maybe).  The proper measurement is already here in this thread.

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Well that seems to be a simple solution. Still heavy winter here so i still have a couple of months to get it sorted out. Thats only one issue on the way to roadworthy im sure. 
thanks for the helpful suggestions 

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Sure thing, let me know how it works out.  I'm still academically interested in what the root cause is here but so far my curiosity hasn't been as strong as my desire to drive my car. 

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On 2/28/2021 at 1:10 PM, Sailor Bob said:

I read the full 5 page thread. It seems to me the clutch kits from zsource may be the culprit issue. Too late and messed up for a return. Any idea where is can source the correct clutch assembly to use original gear/sleeve? Ild be satisfied to pay the additional cost to buy another as long as it works.

Looks like you can get one at Napa. 

https://www.napacanada.com/en/p/NCF1106029?partTypeName=Clutch+Pack&impressionRank=1&keywordInput=clutch

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During the past months I have replaced the clutch assembly in a 74 240z, 78 280z, and a 79 280zx.  I ordered and received all three clutch kits from Zcardepot and all three worked just fine!  

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31 minutes ago, mayolives said:

During the past months I have replaced the clutch assembly in a 74 240z, 78 280z, and a 79 280zx.  I ordered and received all three clutch kits from Zcardepot and all three worked just fine!  

Wouldn’t the 74 be a 260Z?

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