Tom:
Thanks for the in depth info. I know I have a
"non-smog" 7.5 distributor however I will also be
installing a Pertronix unit. Should I look to do
anything different or just stick with the 16 BTDC?
Rob
--- Thomas Walter <ra0618@email.sps.mot.com> wrote:
> 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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