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MY Answer--Clutch Slave Cylinder "Throw"

To: Roadster List <datsun-roadsters@autox.team.net>
Subject: MY Answer--Clutch Slave Cylinder "Throw"
From: "David R. Conrad" <conrad1@gte.net>
Date: Sun, 28 Sep 2003 20:05:36 -1000
"David R. Conrad" wrote:

> "List":
>
> Sparing you the gory details of my problem, is there anyone out
> there in "roadsterland" who knows what the "throw" of the clutch
> slave cylinder should be, or lacking that, what throw "works for
> them"?.
>
> My throw is 9/16ths of an inch, which appears to be inadequate.
>
> Thanks,
>
> Dave
> '68 1600
> Kailua-Kona
>

I was hopeful, but I wasn't exactly "overwhelmed" by the number of answers to
my question ;-).  I'll share my findings.

>From the geometry of the linkage, and my own measurements of one SPL-311, I
calculated that the maximum (theoretical, no "slop") slave cylinder "throw"
should be 0.92 inches.  Because of the 5/8" to 3/4" piston diameters of the
master and slave respectively. the slave moves 69.5% of the master movement.
Mine traveled about 9/16ths inch which was not sufficient to provide release
bearing clearance, and at the same time, sufficient "release" to allow non
interference, that is, "grindingless" shifting.

In my spare parts, I had a "mystery" clutch master cylinder (also made by
Tokico) which was, in many respects, very similar to that which is stock in the
SPL-311.  It had a unique feature, an adjustable "push rod".  (It is shown in
the "attachment", which will be "stripped" for List addressees.  I will be
happy to supply to individuals if requested.)

I modified this adjustable push rod so that it could be substituted to the
stock cylinder push rod, then installed the MC in the car.

I adjusted this push rod so that it would start immediately moving hydraulic
fluid at the normal start  position of the clutch pedal.

Measurement of slave cylinder movement at full depression of the clutch pedal
was a throw of 3/4 inch.  I figure that's about the "upper limit" of what the
slave cylinder "throw" should be.

I returned slave cylinder clearance (to the release bearing) to be
approximately 1/8th inch, where I had set it when I did my last clutch
replacement.  This clearance had apparently "gone away" over time, unnoticed by
me.

My clutch/shifting performance is greatly improved over what it has been for a
long time.  (One of those things that gradually occurs and you don't realize
the amount of degradation, until you "fix it".)

Dave
'68 1600
Kailua-Kona

[demime 0.99d.1 removed an attachment of type image/jpeg which had a name of 
Chutch MC 2]





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