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RE: spitfire clutch questions

To: Brad Kahler <Brad.Kahler@141.com>, fot@autox.team.net
Subject: RE: spitfire clutch questions
From: Bill Babcock <BillB@bnj.com>
Date: Mon, 19 Feb 2001 14:01:30 -0800
I'm feeling like a non-expert on clutches today because over the weekend I
installed the new flywheel in Peyote, with a new pressure plate and
clutch, new throwout bearing and actuating bushing, and when I was all
done after a full day spent assembling and tweaking, the clutch won't
engage and makes an ugly sound when I depress the pedal. I think the new
bushing is too long. The original one was modified for a tilton clutch and
is even longer. I get to undo all my work, and I'm running out of time.

I don't know spit clutches, but I'll weigh in on the spring--I like having
one. With a properly adjusted clutch you can hear the throwout bearing
pull away from the clutch if you have a spring. Doesn't happen if you
don't. I've gotta think that's good for the bearing. I adjust the clutch
rod until I get a little shake with no spring, then put the spring on.
Doesn't seem to make any change to the pedal stroke. 

-----Original Message-----
From: Brad Kahler [mailto:Brad.Kahler@141.com]
Sent: Monday, February 19, 2001 1:42 PM
To: fot@autox.team.net
Subject: spitfire clutch questions
Sensitivity: Confidential


Race weekend is getting close and we're trying to sort out the last few
details of Susan's Spitfire.  We've run into an interesting
situation/delima with respect to the clutch installation.

The PO had modified and installed a 77-80 steel slave cylinder and the
operating rod that depresses the clutch cylinder piston.  (the 77-80 slave
cylinder is about 1/4" longer than the mk3 slave cylinder)  The cylinder
was modified in such a way as to allow it to be installed about 3/8"
closer to the front of the tranny.  (front being towards front of car)  At
the same time he also lengthened the operating rod by approximately 1/4 to
3/8".  

The facts we do know at this point are the disc has 10 splines which is
stock for the mk3, the flywheel is aluminum and the operating lever that
holds the throw out bearing is stock.  The throw-out bearing appears to be
a stock mk3 throw-out bearing and we're using basically a stock mk3
gearbox.  (all this was verified from various spares laying about)

At this point we do NOT know the clutch disk diameter but will have that
info sometime this evening.

In talking with Nigel at Spitbits we came to the conclusion that possibly
the PO has installed a mk4 10 spline 7 1/4" clutch on a stock mk3 (in
size) flywheel.  This possibly would cause the operating point of the
pressure plate to be moved towards the front of the car by about 3/8".  As
near as I can tell this would necessitate a longer operating rod by about
3/8".  What I'm not sure of is why the PO would need to modify the slave
cylinder to allow it to more 3/8" farther forward also.  

Of course a lot of this is conjecture at this point.  Our goal is to use
"stock" style components if at all possible and eliminate the need for
modified slave cylinders and modified operationg rods.  

If he did use the 7 1/4" clutch I'm assuming it was done so for better
performance.  Would the 7 1/4" clutch be that much better 6 1/2" clutch
which was stock on the mk3?  (my ignorance is showing here!)

It seems to me that if what I'm guessing is true I can see the need for
the longer operating rod which would be required to push the throw-out
bearing forward to be in the correct relation to the pressure plate.  But
what I can't understand is WHY modify the slave cylinder so it can be
moved forward?  This has me baffled!

I currently have ordered a new mk3 slave cylinder and am hoping to get it
to work with the current longer operating rod.

One other item, he also installed a throw-out bearing/operating lever
return spring to (I assume) keep the throw-out bearing from contacting the
pressure plate.  Is this needed or desired under racing conditions?

Any comments or suggestions would be greatly appreciated!

Thanks!


-- 
Brad

http://www.141.com/Triumphs
http://www.141.com/Dodge

1951 Dodge 1/2 ton B3B pickup (being restored)
1953 Mayflower TT29490LDL (almost a driver)
1957 Devin (TR3 based)
1957 TR3 Road Racer
1961 TR4 CT288L (being restored)
1962 TR3B TCF1564L (some day)
1964 Spitfire 4 BFC25720L (of Belgian decent)
1967 TR4A (aka Freddy)

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