jbc426 said

Purchase or borrow a dial back timing light.

The increase in vacuum is the best indicator of what your engine wants for initial timing. Tuning for maximum vaccum at idle is a useful techique to obtain an optimum initial timing point, as it is a very good indication that your motor wants more initial timing. You must also reduce the amount of mechanical advance the distributor adds so as to limit your total advance to about 34 -36*.

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