318 vacuum advance
Why RPM of initial can be important.
Lets say we have the original distributor for '69 Dodge 318.
We set the initial timing to be TDC at 700 rpm.
Below 700 rpm, the timing is TDC.
If we measure the timing at 800, 1000, 1200 rpm, those measurements would fall within the timing given by the advance specifications.
If we took the same distributor and set the initial of TDC at 900 rpm.
Below 900 rpm, the ignition will spark some time after TDC. We'd probably find the timing at 700 rpm to be something like 5* ATDC.
If we measured timing at 1000, 1200, 1400 rpm, we'd find it about 5* less than when the initial was set at 700 rpm.
Why RPM of initial can be important.
Lets say we have the original distributor for '69 Dodge 318.
We set the initial timing to be TDC at 700 rpm.
Below 700 rpm, the timing is TDC.
If we measure the timing at 800, 1000, 1200 rpm, those measurements would fall within the timing given by the advance specifications.
If we took the same distributor and set the initial of TDC at 900 rpm.
Below 900 rpm, the ignition will spark some time after TDC. We'd probably find the timing at 700 rpm to be something like 5* ATDC.
If we measured timing at 1000, 1200, 1400 rpm, we'd find it about 5* less than when the initial was set at 700 rpm.
