Re: [T3] Which Distributor?

["Dave Campen" <dave@campen.eurobell.co.uk>]

Hi Gary M.,

I was just clearing out the old e-mails on the PC, and remembered this
discussion. I just found the left-hand inlet manifold to go with the
dual-vacuum dissy, which has a vacuum take-off on the rear face. If you're
going type4 I don't expect you'll need it, but it's here if you do.

I take it you got back home okay. My car developed a strange vibration at
55mph that felt like the front wheels were falling off. A sort of
up-and-down bumping sensation. I stopped and nothing was falling off, so it
may be that my newly fitted and balanced tyres have gone out of balance. For
the moment the cure seems to be to drive at 50 or 60. It's just the bit
in-between that causes problems.....


----- Original Message -----
From: Jim Adney <jadney@vwtype3.org>
To: <type3@vwtype3.org>
Sent: Wednesday, June 06, 2001 4:16 PM
Subject: RE: [T3] Which Distributor?


> On 6 Jun 2001, at 9:22, Miller, Gary (G.) wrote:
>
> > With dual vacuum dizzy:
>
> > Advance hose disconnected: idle advance 5¡, 2000 rpm = 18¡, 3000
> > rpm = 24¡, 4000 rpm = 30¡
>
> > Advance hose connected: idle advance 5¡, 2000 rpm = 25¡, 3000 rpm
> > = 40¡.
>
> From these numbers, as well as your vacuum measurements, I
> think it is likely that the vacuum port you are connecting the dist to
> is not correct for this dist. These distributors DO NOT connect to
> straight manifold vacuum. They need to connect to a drilling that is
> carefully positioned in a particular place relative to the throttle valve.
> With the proper positioning you will have ~30 deg mech adv at
> speed, plus 10 deg additional, IF the engine is under light load
> (cruising.)
>
> Since you have a vacuum gauge, connect a long hose to it so you
> can watch it while you drive (you can leave the vac adv
> disconnected for this test.) If you can verify that the vacuum pretty
> much disappears at idle as well as at half throttle or more under
> any driving conditions, but maxes out while just cruising at a
> steady 50-60 mph, then you should be fine.
>
> The point is that the 30 deg limit really only applies to an engine
> under full load, which is what a RACE engine sees all the time,
> unless you're braking. Under partial throttle the engine can safely
> accomodate more advance and get better fuel economy in the
> process. Thus the vac advance portion of the late dists is a fuel
> economy device.
>
> > Crank angles were calculated from measurements from existing, known
notches on the pulley)
>
> This is reasonable. The |    | | |  notches are at 0, 7.5, 10, & 12.5
> deg.
>
> -
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> USA
>
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