Where should clutch Engage on 1977 280z

[stacym]

Hi everyone....I just bought a 77 280z. Its from Texas..Great shape no rust and runs very well. However, I have a question on the clutch. I owned a 76 when I was in college a very long time ago. With this Z the clutch engages pretty far up when releasing the clutch pedal. How can I adjust it so that it grabs a bit closer to the floor? I tried to find an answer in all the clutch forums but I failed. the clutch on this car is relatively new, but I would like it to catch a bit closer on release..

Thanks

Mark

[Jarvo2]

I recently put a '77 clutch, plate, and collar on my 240z and experienced the exact same thing It seems like the clutch engages/disengages within the first third of travel from the top. Eventually I'll switch back to an earlier clutch, but for right now this seems to be the way it works.

[EuroDat]

Hi Mark,

Welcome to the club and grats with your purchase. Like to see some photo's

I have a 280Z and I agree with Dave. The clutch disengages higher than the earlier 240Z. The 280Z pressure plates is different compared to the 240Z.

If the PO hasn't been changing parts and mix matching between models then the clutch pedal will be the only section you can adjust. You can find the procedure to adjust it in the FSM which you can download here XenonS30

See section CL-6 Clutch pedal adjustment. Make sure the return spring is working properly and the pedal moves freely.

Another simple check, is to push the clutch fork back into the slave cylinder. It should push in a little, maybe 10mm can't remember the exact figures for a new clutch. Check the reservoir for capacity, it might overflow if its full.

If you can't get any free movement there, you may need to adjust the pedal. The pedal is not releasing the fluid back in the master cylinder. That can cause your problem and will also allow the clutch to slip and increase wear on the release bearing.

I changed mine to a 240mm clutch out of a 2+2. It feels a lot firmer and a has a lot more grip.

Chas

[Zed Head]

Since the slave and master cylinders are self-adjusting to take up all play in the hydraulics, the only adjustment there is would be the pedal. You can extend the stop screw to drop the pedal. Otherwise, engagement point would be a function of the clutch disc diaphragm spring, I believe. It expands the two friction surfaces so that they make contact early, then full force is achieved when the spring is eventually fully compressed. Pretty sure that I've read that the clutch disc spring can lose it's temper if overheated. This would give a disc that doesn't apply much friction until the linkage was fully released. My understanding as of this moment.

In short, a new clutch disc might help. Maybe.

[zKars]

If all else fails, follow the instructions in the factory service manual. (link in my signature below to xenons30.com).

It's pretty much a matter of setting the length of the clutch master push rod that's attached to the pedal arm. The stop screw/bumper only adjusts the 'up' resting position of the pedal when your foot is off of it. Do not use this to adjust the clutch free point. Shorten the rod to lower the pedal position where the clutch engages. (lets see, shorter, have to push it further to get same volume to release clutch, so the friction point is now closer to the floor. yeah, I think that's right...)

This does assume the clutch and hydraulics are good condition.

[stacym]

Thanks everyone...I will check it out as soon as I get a chance. The clutch does not slip and it engages fine. I just was hoping to be able to make it kick into lower in the clutch than waiting till it gets up so high. Maybe I am just getting old. I had a 76z back in my youth and I just dont remember the clutch being so far up to engage...Thanks for all your suggestions...I will post some pics soons.

[Zed Head]

Otherwise, engagement point would be a function of the clutch disc diaphragm spring, I believe. It expands the two friction surfaces so that they make contact early, then full force is achieved when the spring is eventually fully compressed.

Quoting myself. I dug around and found a good image of the center of the disc. Exedy calls it a "cushioning plate". Halfway down the page here - EXEDY - Clutch Info

[EuroDat]

Thats a great link you posted Zed Head. Clearly shows all the inner workings of the clutch assembly.

I didn't think the cushioning plate made that much difference to the "height of" engagement. It was more the duration of engagement and not just an on / off engagement like you get with performance clutches which don't have it at all.

I beleive the centre point of the diaphragm spring has an effect. If you get the chance to compare the (240Z with the 280Z) model pressure plates, you will see the fulcrum point is a little further towards the outer section. I think Datsun did this in there general move to "refine" the car and slowly move away for that sports car feel the 240Z had. The 280Z pressure plates have the same clamping pressure, but then engage at a higher point and have a softer pedal.

The disc in the early 240Z series 1 had little cushioning effect. Going back to the early 1980's. My best friend had one and the clutch engaged low. We had the clutch out several times and if I can remeber correctly, we were surprised at how little cushion effect it had compared to the monaro 350GTS I had, but we were told that was normal.

I wonder if putting the 240Z pressure plate in the 280Z will give it that effect. They both have the same clamping pressure.

[Zed Head]

I don't know how much effect the cushioning plate would have. You're right about the pressure plate. The disc and pressure plate are most likely designed as a set.

I knew there was another name for the plate and found it, it's "marcel spring". Found another picture also.

The picture is from this thread (Southbend...), which has a lot of griping and misinformed comments in it but also has some insight on the function of the marcel spring. Might be getting off-topic but you don't get many opportunities to talk about the odd little pieces. Post #21 might be the most informative but he doesn't give a reference. The Google could probably find it. (Found it - http://www.btc-bci.com/~billben/clutch.htm).

Also found the original source of the picture - http://www.mooregoodink.com/news/rams-powergrip-clutch-greater-clamping-pressures-without-sacrificing-drivability/

Edited February 22, 2014 by Zed Head

[EuroDat]

That is an interesting read, by that I mean post #21 in Southbend. The rest of the thread seems to be a rant over his clutch not performing to his expectations.

I never knew it was called a marcel spring btw. Ive learnt something today:bulb: Datsun probably increased the size of the marcel spring in the S30 model over the years.

I can't remember what the compressed distance was on the 240Z disc. We clamped the two in a bench vice to measure how far they compressed and measured them. The monaro clutch compresed a lot more.

Chas

Edited February 22, 2014 by EuroDat

[Mark Maras]

If you have adjustable rods on the master and slave cylinder, my 260 does, adjust the slave cylnder until you have about an 1/8-1/4" freeplay. Push hard on the end of the release lever, you'll feel it. The freeplay insures that the release bearing won't ride the pressure plate at all times. Next adjustment is the master cylinder, under the dashboard. Set it to the pedal engagement height of your preference. This is the point that there is no more freeplay and the release bearing is touching the pressure plate. I don't remember nor did I look to see if there is a pedal height adj,, there probably is no need to change this.

Mark in Portland

PS You could also skip all this and just move your seat back a notch.

Edited February 23, 2014 by Mark Maras
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