re: Stupid timing light questions

[Dana Loomis <dloomis@domain.elided>]

In AD V8 #1275, Biba wrote: 
>Picked up a new timing light at Sears today (Model No. 21023, top of the
>line, at least in Pasadena). I'm less than impressed. Am sure it is
>doing what it is supposed to do. I paid the extra 20 bucks to get the
>dial on the back which apparently one always sets at 0. Ergo, why even
>bother with a dial (except to sucker guys like me into thinking it Must
>be better)?

There are no stupid questions, only opportunities to learn something (there
Biba, do you feel better?).  The dial on the back makes the strobe fire out
of phase with the spark impulse by an angle you specify.  If you want to
set the timing to 15 BTDC at idle, for example, twist the dial to 15, run
the engine at idle, and use the timing light to set the distributor so the
TDC mark lines up with the pointer.  This feature is nice to have when
you're working on a car that doesn't have timing marks where you want them.  

Biba also asked about the Marelli Plex distributor: 
>Didn't someone recently say in essence that the advance
>mechanism on the MarelliPlex distributor sucked? I also gathered it did
>so from birth.

I think the gripe about the Plex is not that it doesn't have enough total
advance, but that it gets there too slowly.  The old Shankle catalog used
to include graphs showing advance curves for various distributors, and, as
I recall, the Plex had a flatter curve than the stock Marelli unit.  If
everything is working correctly, however, the maximum advance should still
be near the factory M mark.
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