Brad,
Re: slave cylinder mods
It sounds like you're dealing with evolution... the slave cylinder was
probabaly modded early in the process until Bert (or his predecessor)
figured that more throw was needed, hence the extended push rod.
Since you're running such a mix of std and custom components, best advice is
to find a combo that releases the clutch somewhere near the floor and isn't
slipping. The setup in use in 1998 actually seemed to work well.
As to the larger diameter clutch disc, two thoughts. First, the larger will
transmit more power (torque at clutch slip is a function of clamping
pressure and surface area... the larger the surface means more torque!).
Second thought. The Mk IV setup may be easier to track down (never had to
buy an early clutch setup new)...
Cheers,
Jim
'76 Spitfire DM
> -----Original Message-----
> From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net]On
> Behalf Of Brad Kahler
> Sent: Monday, February 19, 2001 3:42 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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