Rob,
Look for a decent brand name timing light with a "dial
back" adjustment feature.
It should have the inductive clip on type trigger (slips
over plug #1). I would recommend buying a "made in USA"
brand, but it has been so long I have no idea what is
available.
There are two types of distributors:
Early (normally found in '66-67.5 model vehicles). The
advance cam (hidden by the breaker point plate) will have
7.5 stamped on it. These distributors are set to 16 BTDC
at idle.
Late ('68-'70 USA market vehicles). They will have the
advance cam with 17.5 stamped on it. These distributors are
set to TDC (Top Dead Center) - which is the biggest notch
on the pulley).
In either case, disconnect the vacuum advance line from
they distributor and plug it. I like tapping the starter
until I can see the "big notch" on the crank pulley. I will
clean it with a little wire brush, and put a dap of white
paint in the notch. Let the paint dry.
Start the engine and warm it up.
With that nifty little advance dial you can "dial in the
advance" by a knob on the back. Makes life easier as you
are always looking at the big notch.
As the car is at idle speed (650-700 rpm) you should be
able to "match up" the big notch and pulley mark. The
early cars will have the knob set to "16" and later cars
to "0" when the timing at IDLE is correct.
Now have a friend REV THE ENGINE! Put it up to about 4,000
rpm and check the timing. It should be from 31 to 35 BTDC
on your dial reading. DO NOT EXCEED 35 BTDC!
For the first time setting the distributor I recommend backing
off the timing so it only reads 30 BTDC. There are a lot of
factors that determine maximum advance for timing: including
the compression ratio; grade of fuel; engine temperature;
air temperature; camshaft being used; exhaust system; and
additional items.
Once you have the timing confirmed for maximum rpm, you should
go back and check at idle again. Everything OK?
Now, fun, hook up the vacuum line. Rev the engine and let
it return to idle. You should notice the distributor having
more total advance at higher rpm, and slowly returning back
when the idle is let go. Nice smooth action on the part of
the ignition timing. I find those breaker plates quite often
have "frozen up" or will act very erratic. Distributor maintenance
is often overlooked. I have the distributor faq that discusses
that in more detail.
Cheers,
Tom Walter '68 2000
Austin, TX
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