Larry,
You can measure the advance using a timing light, but
you have to figure out a way to extend the scale.
Use a tape to measure the circumference of the pulley,
then divide by 72 to get the distance between 5 degree
increments. You can either mark the edge of the
pulley, or attach a scale adjacent to the pulley. I've
used white paint on the edge of the pulley, and made
marks with a sharpie marker. Or a paper scale with
marks would work as well.
Disconnect the vac advance, and then observe and
record the centrifugal advance. Record at 500 or 1000
RPM intervals if you want to quantify this.
Now, back at idle, apply vac to the distributor (use a
mity vac, or tape a piece of hose to end of a vac
cleaner, etc.) and observe the advance. Use a vac
gauge if you want to quantify this.
Add the max centrifugal and max vac advance to get the
total. This will tell you where to set the initial
timing to get 35 degrees total.
BTW, if you do disconnect the vac advance, it's
recommended to secure the breaker plate to the
distributor housing, to keep it from flopping around.
A simple way is to use a small metal L bracket. This
is easy to remove if you change your mind.
Carter Shore
--- Larry Elswick <sos@kymtnnet.org> wrote:
>
> I've researched the archives but I'm still
> not clear on this issue. I have a 76 Spit
> with a functioning vacuum retard unit on
> a 45DE4 distributor with a Lumenition
> electronic ignition installed by PO.
> I installed twin HS-4's. Should I disconnect
> the vacuum and plug the port for better
> performance? Ted Schumacher said I needed
> to know the total advance the distibutor would
> deliver and not to exceed 30-35 degrees total.
> Thanks!
> Larry
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