[FC] Clutch linkage - early vs. late

Sun Oct 23 11:36:53 EDT 2005

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

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
>
>
>
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