[T3] My new Carbs

["Mark Seaton" <Markse@mo-sys.com>]

<x-charset iso-8859-1>Well I finally fitted my newly re-furbed carbs and am having a few problems.
As per a previous post, they are an unmatched pair of the older style
(piston throttle advance pulloff type).
The left one is a '66/'67 model with 132.5 main, and 127.5 air correction
jet, whilst the right is a '68-'71 type with 127.5 main and 120 correction
jet. I decided to try them out in this configuration, despite Neils advice,
as I kind of liked the idea of running the left bank a little richer  to
keep temps down. Now I'm beginning to wander if I should reconsider!

After fitting, it took me ages to get the engine running stable enough for
me to go round the back and fiddle.I ended up opening up the idle mix screw
loads of turns more than the recommended 1.5. This was one of the things
that I had hoped would be sorted out by the re-bushing of the throttle
plates. The Right carb is fairly responsive to adjustments, but the left is
not really at all. In fact I'm really not sure if I've got the mixture right
at all!

The car is now a real devil to start. I think the balance is pretty  good
because she runs very well at idle and at speed once properly warmed, but
she was much easier to start with the old carbs. I was very careful in
setting up the choke and throttle advance. I left the choke butterflies out,
but left the shafts and mechanism in place with the heaters hoping to
benefit from the lifted throttle at start-up, but I really don't think this
is working properly. I will try putting the flaps back in at the weekend and
see if this makes a difference.

My real reason for the post though was that I have a problem in the mid
RPMs. The idle is fine but if I slowly increase the throttle I go through a
very rough patch like the carbs are really out of balance- if I hang around
at that speed the engine threatens to stall. If I go beyond that speed the
engine gets smooth again! so I don't think its balance. I'm wondering if it
is something to do with the vacuum advance? Is it possible that different
era carbs had different drillings for the vac advance, and that a '66/'67
carb won't work properly with my '73 mech/vac adv dist? If so I'm going to
be very disappointed as I prefer these carbs to my '73s. Or is this
something to do with the unbalanced jetting I'm using (its more unbalanced
than ever originally spec'd though VW did spec them with different jets pre
'71)

Any advice appreciated, though not to switch to FI please! I'd love to but
can't easily.

Mark Seaton
'73 TA London

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