etc.

["Melissa & Jim" <jadney@vwtype3.org>]

------- Forwarded Message Follows -------

Type IIIers,

I'm afraid I've been trying to learn how to use a new email program,
Pegasus, if anyone cares, and in the process find that a whole bunch
of topics I commented on to this group got lost on my machine before
they ever got out of here.  I'd like to mention some of them briefly
now.

Vacuum advance:

Keith Park mentioned that the vacuum advance was really a vacuum
retard.  I don't agree.  If you look at the construction, or watch
your timing light while you suck on the hose you'll see that greater
vacuum gives greater advance.  That fits my definition of vacuum
advance.  Of course the 72 T3s had both vacuum advance and retard, and
all the FI cars have mechanical advance as well.

Why use a 009?

For most people it is a macho thing.  However, there is a good reason
to do this:  If you have just installed a special carb, you will find
that it either has no pickoff point for the vacuum or the vacuum it
provides is not right for your existing vac adv.  The end run around
this problem is the mechanical advance 009.  On the other hand, if you
look at the Bill Fisher "How to Hotrod..." book you will see that the
68-9 FI dist has one of the best mechanical advance curves of any
distributor including the 009.  This distributor, the 311-905-205L,
should be in strong demand for high performance cars, but it lacks
that crucial macho factor.  It also has the additional advantage of
having the vacuum advance, which will add improved gas mileage at low
throttle cruising.

20W50 motor oil:

The siren song of thicker oil is an ever popular mantra, but while it
will make your oil pressure gauge read higher, its only other end
result is to increase the power input required to drive the oil pump.
Since this power comes directly from the engine the result is less
power to the wheels.  This is another advantage of Berg's pressure
relief full flow pump cover.

The pressures in the bearings where the oil is doing its work are much
higher and are generated locally by the hydrodynamics of the journal
bearing.  In fact the oil feed holes in a journal bearing have to be
carefully placed in the low pressure areas to allow oil to actually
enter the bearing.  There's a lot of carefull engineering that went
into this.

OTOH, heavier oils can be useful for minimizing leaks, but this is
just a stopgap [literally!] solution.

Gene Berg has a nice paper on the advantages of lighter motor oils.

A fresh comment on Pertronix ignitions:

I installed a Pertronix ignition on a customer's 71 sqbk today.  It's
a nice looking assembly, but they include a special rotor that you
have to use.  The included rotor is a genuine Bosch non-suppressed
rotor with the insulating skirt machined away and a special sleeve
pressed on in its place.  The sleeve includes the 4 magnets that trip
the Hall effect sensor in the ignition module.  Everything seems quite
nice except that you can only buy a replacement rotor from Pertronix
and one other little problem.  Since the magnets in the skirt trigger
the ignition, the must be positioned very close to exactly 90 degrees
apart.  To check this, I timed the engine on #1 and then switched the
timing light to #3.  I found that #3 was advanced by about 5 degrees. 
I have no way of checking 2 & 4.

This is not quite the level of precision I would like to see.

Enough for now.  Thanks for reading.

Jim
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       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org              jadney@vwtype3.org
                             Laura Kepner-Adney
                             Madison, Wisconsin
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