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Re: [T3] Weber 34's and which dizzy to use!

On 31 Dec 2003 at 22:58, tristessa wrote:

> I've done some (admittedly unscientific) testing on a couple of my
> VWs, my '65 T1 (1776, header, dual Kadrons) and a '75 Westfalia (1.8L
> T4, header, 34ICTs (thanks again Brian!)).  On both of them I've
> ditched the 009 and put in a 205-series electronic-ignition (Vanagon)
> distributor, with the vacuum advance disconnected.  Both times the
> result has been "good", but since the Westy was recent it's fresh in
> my memory.  It has noticably more power, better drivability, and it
> even mostly quit popping up the carbs.

It's fairly easy to add a bit of objectivity to all of this by just looking up 
the advance curves that are available in the Bentley manuals for all the VW 
since about 68. I think the Bill Fisher book also includes the curve for the 
009, but I've been meaning to check that. 

There's little about these curves that is mystical or not understandable. You 
just have to realize that they are all in distributor degrees/rpm and that you 
want to multiply by 2 to get crankshaft degrees/rpm.

In general we want a rapid, smooth advance that gets you about 30 degrees of 
advance by 2000-2500 rpm so that you can time the idle to about TDC and still 
have about 30 degrees of total advance at full rpm.

We also need to understand that the 30-34 deg limit is only for full throttle. 
The engine can handle about 10 deg more at light throttle, which is what the 
engines with mech/vac advance dists do to improve economy at cruising speeds. 

Vacuum advances are tricky, because we don't know how the vacuum progresses 
with load on YOUR car. If you want to use a vacuum advance you pretty much have 
to stick with the one that the factory provided with your carbs, because they 
are a matched set.

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org

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