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Want a larger Clutch master cylinder than 5/8


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The car is a 1971 240z  Rb26 swap

Can't answer swap specifics, but this Wilwood part is a direct bolt-in (mostly).  You can swap the stock pushrod into it, and if you add a 1/8npt 90deg street elbow and a 1/8npt  to 10mm inverted flare adapter, the stock line even comes out in the right place.

http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Compact%20Remote%20Flange%20Mt%20Master%20Cyl-1/8%20NPT%20Outlet

 

Here's a couple of related posts:

 

http://forums.hybridz.org/topic/122481-wilwood-compact-clutch-master-cylinder-no-260-10374/?hl=%2Bwilwood+%2Bclutch

 

http://forums.hybridz.org/topic/94004-easy-clutch-master-swap/?hl=%2Bwilwood+%2Bclutch  (different master cylinder, but the pushrod swap is the same)

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Having a problem with stock clutch master cylinder pushing the pin of the stock RB25 transmission  slave cylinder the max.  Interesting in knowing if anyone has had this problem and a cure may be a larger bore cylinder?

 

I have this problem as well, BUT I also have a different slave cylinder. From other posts, people have said a certain year corolla one works (AE71?). I went with that, and I have the same problem. It is however a 13/16" slave. The stock RB25 slave was 3/4". I have ordered the original RB25 slave and will see if that helps the travel problem. I could drive the car with the 13/16, but there was no dead zone at the bottom of travel even with all the slack taken out.

 

Interestingly, the Nismo Spec slave is 13/16" as well to decrease pedal effort. Perhaps it requires the nismo slave as well, or it's expected that the performance clutches have less actual throw.

 

Let me know how you make out with the issue. Make sure you you have the oem 3/4" slave. From my reading and searching, the RB25 had the same diameter master cylinder as the S30, so it shouldn't be an issue.

 

Mark

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I have this problem as well, BUT I also have a different slave cylinder. From other posts, people have said a certain year corolla one works (AE71?). I went with that, and I have the same problem. It is however a 13/16" slave. The stock RB25 slave was 3/4". I have ordered the original RB25 slave and will see if that helps the travel problem. I could drive the car with the 13/16, but there was no dead zone at the bottom of travel even with all the slack taken out.

 

Interestingly, the Nismo Spec slave is 13/16" as well to decrease pedal effort. Perhaps it requires the nismo slave as well, or it's expected that the performance clutches have less actual throw.

 

Let me know how you make out with the issue. Make sure you you have the oem 3/4" slave. From my reading and searching, the RB25 had the same diameter master cylinder as the S30, so it shouldn't be an issue.

 

Mark

Note as well that a smaller slave results in more travel. Opposite effect from a smaller master. Probably known, but thought I'd make sure it's understood.

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  • 3 weeks later...

Thanks for all halls help guys!

Ended up there was no problem with with the hydraulic system at all. We had a "stuck clutch disc", first time I've ever heard or had this problem. That being said the factory 5/8 clutch master cylinder will work the factory 3/4 rb25 slave cylinder just fine. And if you ever have a stuck clutch disc, do this..

1. Put the car in 4th gear and pull up the e brake

2. Push the clutch in and try to start the car.

3. Hopefully the starter had enough torque to break the clutch disc free from the flywheel or pressure plate.

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Given how hydraulics work, stroke out is a function of stroke in and my recollection was bores were very close on RB and S30 diameters.

Your revaluation confirmed what I thought.

Thanks for posting what you found! It's what I suspected but without the bore size differential I couldn't do the calls to check...

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