[FC] Clutch linkage - early vs. late

[James Davis]

The late model system has the clutch cable terminating in the cross 
member where as the early model system has the clutch cable going 
under the cross member to the idler lever. The 61 Ass'y manual, 
Section 6 sheet 21.00 shows the correct early arrangement.  Rad is 
correct in that when I changed from a 3 speed trans to a 4 speed in 
his Greenbrier, I used an early setup (the Greenbrier was purchased 
with a 62 car engine and 3-sp) because that is what came on my 61 
Rampside and I had a spare.  Only later did I find out abut the much 
different clutch cable system of  the late FC's.  Of course the late 
63's use a hybrid system, part of the new and part of the old.  And 
you thought all FC's were the same ;-).
Jim Davis



.At 10:36 AM 10/23/2005, you wrote:
>Rad,
>
>Very interesting--thanks!
>
>You bring up an interesting point. The assembly manual also does not make it
>clear how to tell the early vs. late pull rods. I *assume* I have a late one
>since the bell crank and etc. are not on my rig--but I don't know for sure.
>Do you have an easy way of determining this? The rod appears to line up
>properly with the end of the clutch cable and does not hang down noticeably.
>
>I guess I also don't know for sure whether I have a late FC release fork and
>fork pivot ball...
>
>--Kent
>-----Original Message-----
>From: corvanatics-bounces at corvair.org
>[mailto:corvanatics-bounces at corvair.org] On Behalf Of Rad Davis
>Sent: Saturday, October 22, 2005 8:45 PM
>To: The Corvanatics list
>Subject: Re: [FC] Clutch linkage - early vs. late
>
>Kent,
>
>I have walked down that particular road:
>
>When my father gave me the Twinki 15 odd years ago, it was fully functional,
>but some of the parts were an interesting mixture.
>
>Dad's only prior FC experience was with his '61 rampside.  Lots of the
>late-model-specific parts were missing from Twinki when he got it, so he
>substituted the commoner early parts and some creative fabrication as
>necessary.
>
>The clutch linkage was mostly early FC, with a custom pull-rod (don't have
>my manual handy for the proper name - I mean the threaded part with the
>clevis pin hole on the other end that goes into the bellhousing) made from a
>straigtened car part.  The return spring "extension" was a piece of
>carefully-formed coathanger wire made to match the one on the Rampside.  It
>had the cable bracket on the transmission crossmember (even though it had
>the correct crossmember with the hole), and an NOS early pivot arm assembly
>he'd gotten somewhere.
>
>I really didn't like the way the clutch worked.  As it happened, he had the
>wrong mixture of clutch parts resulting in a too-long clutch release travel,
>but I didn't know that until I took everything apart and measured,
>eventually converting to the late car/late FC clutch, release fork, and fork
>pivot ball.  I also didn't like that the clutch cable and linkage stuck down
>so far.  I had to pick shreds of grass out of the assembly on more than one
>occasion after parking on turf.
>
>I lucked into all the right linkage parts (and a bunch of other detail
>parts) on a '64 GB Deluxe Jerry McKenzie and I parted out in the mid '90s.
>Luckily, the parts van had almost all the odd parts the 63-65 vans came
>with.  Also luckily, Jerry had a '61, so didn't want any of them.  I didn't
>know that the Z-shaped bracket was so rare.  It would be trivial to
>reproduce.  I also didn't know that the late dust cap wasn't properly
>documented.  It would indeed be a real challenge to get everything together
>without that special tab for the cable return spring.  I suspect that the
>late dust cap could also be done as a cottage reproduction given a supply of
>early/car dust caps.
>
>My best guess about the early "extension" and that funny long L-bracket tab
>on the dust cap is that the spring was used on something that was a lot more
>common than FC corvairs.  Perhaps Chevy truck clutch return springs of the
>era?  An interchange manual of the era and the spring part number might be
>helpful.
>
>As for why GM did it that way, I've always had the feeling that the first
>design mechanism was made to minimize investment in custom parts.  It
>certainly isn't a rational design given a clean slate.  The transmission
>cross member is the same as the early car part.  The spring looks like it
>was sourced somewhere else as well.  It may well be that the second design
>was really the original design but was shelved because of the retool cost of
>adding that hole in the transmission cross member.
>
>-- Rad
>