[FC] Clutch linkage - early vs. late

[Rad Davis]

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




At 07:59 PM 10/22/2005 -0700, you wrote:
>Hi,
>
>I have been working on getting the correct parts for the clutch linkage for
>my '64 Rampside. It had been a mishmash of early FC, late FC, and car parts.
>I think I finally have all of the right parts. Quite an odyssey.
>
>The first thing that made this an adventure is that one of the parts, a
>"Z"-shaped bracket that holds the front of the return spring (the rear
>spring), was hard to come by. Folks told me that most FCs so equipped ('63
>and later for sure and probably very late '62s) do not have them any more;
>they got lost and it's possible to hook the spring in another fashion so the
>bracket is not critical.
>
>The other thing that made this quite an adventure is that the metal dust cap
>on the transmission changed when the rest of the linkage changed but the
>drawing in the assembly manual was never updated. The part number is
>different but it was hard to tell how it changed. Here are some photos
>showing the dust cap for a car, early design FC and late design FC:
>
><http://www.corvairkid.com/articles/images/Clutch linkage dust cap 001.jpg>
>
><http://www.corvairkid.com/articles/images/Clutch linkage dust cap 002.jpg>
>
><http://www.corvairkid.com/articles/images/Clutch linkage dust cap 003.jpg>
>
><http://www.corvairkid.com/articles/images/Clutch linkage dust cap 004.jpg>
>
>The car dust cap has no bracket; the early has the short bracket; and the
>late has the long bracket.
>
>The bracket design change is very intriguing. Both designs use the exact
>same spring; for some reason the early design bracket has a short arm and
>then an "extension" (that's what the assy. manual calls it) that takes up
>the extra space. The extension is just a simple oblong wire loop. This
>design seems really odd to me. The late design, where all of the reach is in
>the bracket, seems much more sensible. Does anyone know why the early design
>is the way it is?
>
>If you want to see exploded views of the two designs, look in the 1961 FC
>assembly manual in section 6, part C; for the late design, look in 1962 or
>later, section 7 part C. (It was a late year change in '62; only the page
>for the second design was kept.)
>
>--Kent
>
>
>
>_______________________________________________
>Corvanatics mailing list
>Corvanatics at corvair.org
>http://www.vv.corvair.org/mailman/listinfo/corvanatics
>This list sponsored by the Corvair Society of America, 
>http://www.corvair.org/