[FC] Clutch linkage - early vs. late

Sun Oct 23 13:08:59 EDT 2005

Hi Kent, my parts book shows:
0.787 ROD, CLUTCH FORK PULL

1   3780836  1961/R1200 - FIRST JOBS - 12-1/2 OL
1   3786914  1961/R1200 - AFTER JOBS
                     1962/R1200
1   3827690  1963-65/R1200

so, there's 3 different ones...
Shaun

----- Original Message ----- 
From: "Kent Sullivan" <kentsu at corvairkid.com>
To: "'The Corvanatics list'" <corvanatics at corvair.org>
Sent: Sunday, October 23, 2005 9:52 AM
Subject: RE: [FC] Clutch linkage - early vs. late

> Right--I am definitely aware of the through vs. under cross-member part. I
> am wondering about the pull rod that is further back from there--the rod
> with the fine-threaded end that goes into the transmission.
>
> According to the assembly manuals, the first design linkage was used in
'61
> and most of '62. The '62 manual shows the second design and it's a very
late
> change in the production year. The drawings appear to be exactly the same
> for '62 - '65 so I would be interested in details of known differences in
> the second design...
>
> --Kent
> -----Original Message-----
> From: corvanatics-bounces at corvair.org
> [mailto:corvanatics-bounces at corvair.org] On Behalf Of James Davis
> Sent: Sunday, October 23, 2005 9:35 AM
> To: The Corvanatics list
> Subject: RE: [FC] Clutch linkage - early vs. late
>
> 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
> >
>
>
>
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