Re: [T3] Best dizzy for AT with carbs?

["Mark Seaton" <mark.seaton2@ntlworld.com>]

----- Original Message -----
From: "Jim Adney" <jadney@vwtype3.org>
To: "T3 List" <type3@vwtype3.org>
Sent: Friday, March 21, 2003 5:06 PM
Subject: Re: [T3] Best dizzy for AT with carbs?


> On 21 Mar 2003 at 9:38, Jim Adney wrote:
>
> > What you really want is ~30 deg adv going up that hill, but it would be
nice to
> > up that to ~40 once you're at the top and you can let off the throttle
and let
> > the engine relax again. This is what the later (vac/mech adv) dists do,
and the
> > later carbs that were made to work with them had their vacuum ports
drilled
> > differently so they would provide the right vacuum under the right
conditions
> > FOR THOSE DISTRIBUTORS.

Wouldn't that be that they would need a vac retard to reduce the advance
under strong vacuum/load going up hill?

>
> It occurs to me that the late OE dual carb cars probably have dual advance
> dists. For this to work, these carbs would have to have different vac port
> drillings to give the right signals to this later style of dist.
>
> Can our UK listees confirm that late dual carb engines came with mech/vac
> advance dists?

Yes- well mine did- that is assuming that it is the original dist- but then
again you all know the trouble (read poor mpg) I have been having. Perhaps
its not the original dist? I'll check the part no. and maybe someone could
tell me. I think theres a good chance that it is OE as the engine doesn't
seem to have been messed with too much.

> Has anyone noticed a difference in the vac drilling in late vs early
carbs?

I checked in my box of carb bodies and they appear to be the same- there is
a .6mm hole in the carb body leading in behind the venturi, then running
down a passage moulded into the venturi into the throttle plate, then out a
square aperture on its base- below the throttle disk. But wouldn't that give
you high vac at idle?- this doesn't seem to be the case- maybe its just at
take off when the throttle opens a little and the engine revs causing a
strong vac beneath the partially open throttle? The early and late all
appear the same though the throttle disk and idle transfer drillings are
different. I guess the vac can might have changed?

Mark Seaton
'73 DC Fasty London




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