That feature is probably the single most useful improvement ever added
to any of the aftermarket points-replacement systems, and it's why I
recommend using the Pertronix Ignitor II over the P-I or other modules.
You may not ever leave the ignition on intentionally, but it does
sometimes happen, and it's nice to not have a smoked coil as a result.
Most of the points-replacement units such as the Mallory Unilite,
Pertronix, Crane, Allison, and other modules extend the coil dwell time
significantly. This is one reason why they typically offer better
performance at higher RPM compared to points - there is no mechanical
restriction on the dwell time. However, that effect also causes many OEM
Tiger tachs to read improperly once the module is installed. Since it
works for some people, I think it has something to do with the overall
condition of the tach components - if your tach was marginal to begin
with then adding the Pertronix or other module won't make it read any
better. The tach module that I build (and is available for installation
through Tom Hall if you don't want to send your tach to Canada) works
fine with Pertronix modules because it's not sensitive to dwell.
Regarding Tigerman's post (on the Pertronix distributor) - you should
never set the timing based on initial advance unless you know and have
verified the mechanical timing advance. It's common knowledge that
setting the initial timing a little advanced (i.e. 12 degrees BTDC
instead of 6 or 8) will help the idle and off-idle response, but if you
do that without restricting the total advance, you will end up with a
total mechanical advance (at high RPM and load) that exceeds 38 degrees
BTDC, which is where most smallblock Fords are going to be happiest.
It's better to use a dial-back timing light or else make a timing mark
on your damper at 38 degrees, and set the timing at an RPM where you
know the mechanical advance is all-in. If you do that, and then find the
idle timing is not suitable, you need to adjust the advance mechanism
limits in whatever way your distributor allows.
Theo
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