Clutch fork throw

[Zed Head]

Looks like you've got the math figured out.  You could probably measure more on your old collar and bearing and use the illustrations from MSA and ZCarDepot and figure out if their product would work.  Have to do some scaling and rithmetic and ratios and thinking...

It's probably this one.  More bad illustrations.  Good luck.  Hopefully somebody out here has one.  @zKars

https://www.thezstore.com/page/TZS/PROD/21-2122

[rcv]

11 hours ago, Zed Head said:

...use the illustrations from MSA and ZCarDepot and figure out if their product would work

Good idea, I downloaded Fusion360 tonight and figured out how to use their image calibration feature to get quick dimensions on all of MSA's collars. The big dimension listed is the bearing/spring edge to the ear/fork edge.  The "70-74" looks exactly like the collar I already have, so I'm still totally confused as to why my pressure plate won't work - maybe zcarsource accidentally shipped me a clutch kit for a 75-83 Z/ZX instead of the 70-74 240Z?  My receipt has the SKU as 14400101 which corresponds to "Clutch Kit, 240Z 260Z, 70-74 Coupe" but maybe it got mixed up at the warehouse.  I wish there was a similar chart to mine below that listed the various flywheel-to-spring distances for the various pressure plates.

It seems like my best move is to buy the 42mm "75-83 Z/ZX Coupe Non-Turbo" collar and hope it works.

 

https://docs.google.com/drawings/d/1HuluAj7FVtCVHmtBPNeBAm5UFJZXZPKCaLfyJISMyLM/edit?usp=sharing

Edited July 4, 2020 by rcv

[EuroDat]

Funny, I wrote almost the same thing 7 years ago?

Unfortunately a lot of people measure these collars in a why that makes no sense now. The most important measurement is the 92mm from the flywheel surface of the pressure plate to the contact point for the clutch fork.

Those collar measurements you see 32, 42, 38 and 41 are not very handy to you because they measure the total length from the throwout bearing shoulder. They measure past the tab for the clutch fork.You can figure out what you need with some calculating and refering to the one you have.

You can measure your pressure plate with the throwout bearing and collar and see how far off 92mm you are. Note the difference between your measurement and 92mm. Then measure your collar like in the photo with 32, 42, 38 and 41mm.

Example: If you measure 82mm. That is 10mm short. Then measure your collar at 32mm. You will need the 42mm collar.

Most aftermarket clutchs are based on the 75-83 280Z ZX couple clutches with that pressure plate.

ALL this information is related to the pressure plate height. The picture of all the different collars I posted is very old and explained where all these different heights came from. The problem these days is there are so many Zeds running around with non original clutches and therefore no real relation to the A, B etc trnasmissions.

[EuroDat]

16 hours ago, rcv said:

Actually it looks like I mismeasured the setup on the engine. I was measuring to the bolt pocket on the flywheel which is ~10mm deeper than the friction surface. That means that I almost certainly need the longer collar. Damn I was really hoping to drop the engine in over the long weekend. Ah well. Thanks for the help!

You should to do the measurements with the pressureplate off the flywheel. On a flat workbench is fine. Place the throw out bearing with collar on the pressure plate fingers and measure the height from the clutch fork tabs to bench top.

If the pressure plate is fitted and compressed it will have a different height.

 

[rcv]

9 hours ago, EuroDat said:

Those collar measurements you see 32, 42, 38 and 41 are not very handy to you because they measure the total length from the throwout bearing shoulder.

Ah, I think my picture just wasn't clear. I updated the drawing to make it more apparent that the measurements are from the fork surface of the ears to the edge of the throwout bearing surface (see red markup).  Unless I'm still having trouble getting this concept through my thick skull, I think these are the relevant numbers.

9 hours ago, EuroDat said:

Most aftermarket clutchs are based on the 75-83 280Z ZX couple clutches with that pressure plate.

Yeah that makes sense, I'm betting zcarsource just sent me a 75-83 Z/ZX plate, as it measures ~44mm from the bench to the springs.  According to my chart below, my best bet is the corresponding 75-83 Z/ZX collar which should get me up to 44 (plate) + 42 (collar) = 86mm.  It's not quite 92, but add a few mm for the extra bit of bearing that sticks over and a few mm for my sloppy image measurements, and I think it may just work.

 

[Zed Head]

18 hours ago, EuroDat said:

 The aftermarket industry make one type of pressure plate, but in the S30 series Zeds they had 4 different heights over the years.

I think that you have the math down about perfectly.  EuroDat supplied the final clue to your problem early on.  There is no "70-74" pressure plate (tall plate) available in the common low budget aftermarket.  There are only two kinds now, a 225 mm plate (coupe) and 240 mm plate (turbo and 2+2).

If this forum had stickies this would be a good one.  That's a nice illustration of where to measure.

[rcv]

Great, I'm going to order myself the "75-83 Z/ZX Coup Non-Turbo" collar and see how it fits.  I'll post an update next weekend when the part arrives.

 

As a tangent:

1 hour ago, Zed Head said:

If this forum had stickies this would be a good one

I've been thinking about this. It seems like you and a few others donate a ton of your time to answering the same questions over and over again from newbies like me.  It's a shame there's no good place to easily collect and refine this knowledge.  Throwing up a wiki is a piece of cake these days, and I'd be more than happy to spearhead that. The harder part is getting a critical mass of people to actually contribute to and maintain it.  I know there's the "Knowledge Base" section of this site, but it seems pretty dead.  Maybe I'll make a post in the Chatterbox forum and see if I can get any traction. 

[EuroDat]

I made a pdf with a lot of this info 4 or 5 years ago. I'll have a look for it and see if it needs updating and upload it to the tech section.

It had all the clutch part numbers and most of the dimensions.

[rcv]

I got the longer collar installed, and bolted up the transmission this morning. It’s definitely an improvement as I can actually feel the springs against the bearing now when I pull the fork all the way back.  Should I be able to actually disengage the clutch with my hands in the fork, or would that take superhuman strength?

On 7/3/2020 at 2:02 PM, EuroDat said:

 

If you pull the clutch fork back until the throw out bearing touches the pressure plate fingers and then measure the distance away from the front of the bell housing, you should measure about 115mm give or take a couple of mm.

 

I don’t quite get 115mm - more like 135mm which is at least an improvement over the old measurement of 150mm.  Do you all think this is good enough, or should I pull it apart again and investigate further?

 

[Zed Head]

1 hour ago, rcv said:

 Should I be able to actually disengage the clutch with my hands in the fork, or would that take superhuman strength?

It would take super human strength.  The hydraulic system transfers the power of your leg on the lever length of the clutch pedal directly to the clutch fork.  I can't remember if there's a hydraulic amplification from bore sizes but still, that pedal is pretty long.

Never mind this second part, I removed it.  I didn't really get what was happening.

Looks like you have the tallest sleeve but are getting a lower number.  Almost like you have a short pressure plate.  Not sure what's going on with your setup.  Need to ponder.  Do you have any pictures of the pivot ball in the transmission?  On the front cover.

Edited July 11, 2020 by Zed Head

[Zed Head]

Any chance you put the fork on the wrong side of the sleeve ears?

[Zed Head]

Just for reference.