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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