Clutch master cylinder stroke

[Jeff G 78]

I am rebuilding my '74.5 260Z LeMons car that has been in a barn for 10-15 years and the clutch master cylinder piston is frozen solid. So, I went to my parts stash and grabbed another MC that I could rebuild. I am not sure what year the MC is from since I have parted out everything from '72-'78 Z cars. What I found is that the MC is shorter than the 260Z MC. They are both 5/8" bore, but the reservoir is shifted a bit and the whole unit is about 1/2" shorter. I always thought they were all the same for the S30s. I can't get the piston out of the 260Z MC, so I can't measure the stroke to see if they match.

The auto parts stores only list one MC, so I need to know if the shorter one will work and if a standard rebuild kit (with new piston) will fit it. Our LeMons rules only allow us $500 total, so I can't simply replace the MC with a new one. A rebuild kit is $6 vs. $40 for a new MC.

Longer MC was on 260Z, shorter came from my parts stash and has no name cast in.

Edited August 9, 2009 by Jeff G 78

[geezer]

Jeff - The longer one from the 260z was used up to May '75. In the microfiche there is a NOTE (set substitution) which is:

Assy-cylinder clutch master 30610-E4301 changed to 306-N4200

Assy-tube clutch master 30650-N4201 changed to 30650-N4200

This info is from the 12/79 revised microfiche but should help track down the rebuild kit, which is shown as 30611-N6025 Kit - Repair Clutch Master Cylinder

If you want the exploded views let me know, I can take a few pics.

[Jeff G 78]

So Ron, when I check any auto parts store's website, they all list the rebuild kits as 70-78. I could certainly see the seals being the same, but does the piston look the same?

From what you say, the shorter MC should work fine as long as I can rebuild it.

I do have the Parts CD, but when I tried it today, it wouldn't work. I think the latest Adobe Acrobat Reader is incompatable with the CD. It worked fine a month ago, but now gives me an error when I try to go to any section of the CD.

[geezer]

No, the piston assemblies are different. I can't tell by looking at this what the stroke would be either. The best I can do for you is send some pics of the microfiche, so you can get a better look. I'll email it.

Hopefully, someone reading this will have a good used MC. What do the LeMons rules state about donated used parts? How much time do you have to get the car ready?

[Jeff G 78]

Hey Ron, I just got the microfiche CD to work. I had to disable the web plug-in per the CD's recommendation. Weird, I never had to do that before the Adobe 9 download.

Yes, now I see that the pistons do look different. I guess I will simply get the basic rebuild kit without the piston. I can't imagine the seals will be any different.

As far as parts go, anything that is free via sponsorship, donation, etc. technically counts towards the $500. Used parts aren't going to be scrutinized unless they add performance. Now, if someone were to give me a used Rebello engine or set of Illumina struts for free, they would have a problem.

One thing I am looking for is a '79-'80 ZX distributor so I can dump the points. I have several '75-'78 distributors, but would then have to get a GM HEI module and I've heard the HEI units are lousy for high RPM usage.

The race is October 3-4 in Northeast Ohio at Nelson Ledges.

Of the ten S30s I've had, this is my first 260 and it's quite the bastard child. I can never quite be sure what parts do or don't fit it. Some parts are 280, some are 240, and some are unique. I like my '78 because I always know what works.

The car is pretty clean and luckily, everything comes apart easily since it's from Texas, but all of the hydraulics are shot after sitting for so many years. I poured about a tablespoon of powder out of the brake MC reservoirs. The piston was frozen solid just like the clutch MC. I will replace the seals in the wheel cylinders, front calipers, clutch slave, brake master (spare), and clutch master (spare).