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A buddy and I are having some trouble with his '69 SS396 auto. He recently baught the correct # 1111497 dist. Our problem is, how do we check the advance settings, against what they should be? No one has the SUN dist. machine anymore. We have the factory specs and advance timing light. We are planning to disassemble and clean it, also install a new vacuum unit. The bushings seem OK. what else should we do?

Thanks,
Sam
 

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If you have an adjustable timing light, paper & pencil, and time, its not a problem.

I would write an RPM column on the paper from 1000 rpm to 3500 rpm in 500 rpm steps.

I would outline both TDC on the harmonic balancer and 0* on the pointer.

I then would hook up the t/light and write down the initial timing after firing up the engine.

On the way up to 3500 rpm, I would right down the amount of timing shown. Once I got to 3500, disconnect and plug the supply side of the vac hose.

On the way down to 1000 rpm, I would right the amount of advance shown at every 500 rpm.

Now you have a chart showing the amount of advance with vac and w/out vacuum.

Initial timing plus mechanical timing plus vacuum timing equals total timing.
 

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Typical "total timing" (34-38 degrees) is initial plus centrifugal only (vacuum advance disconnected and plugged); once you map the advance curve, then you can re-connect the vacuum advance and verify that it's operating properly (how much advance it's adding, and at what vacuum level it's fully deployed).
 
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