degrees of timing can be reported in distributor degrees or crankshaft
degrees. Typically, distributor specifications are reported in distributor
degrees, whereas typical engine tune-up specifications are reported in
crankshaft degrees. However, variations on this pattern can occur so it is
important to verify the type of degrees (distributor or crankshaft)
reported.
Figure 2
Distributor testing machines, which test distributors across a range of
revolutions, are of necessity based on distributor degrees, which are one-
half of the crankshaft degrees. Accordingly, if the distributor testing
machine shows the maximum centrifugal advance to be 14 degrees, this
translates to 28 degrees at the crankshaft.
Figure 1 presents the distributor specifications for 1941 Buick
engines. In this chart, all degrees are reported in crankshaft degrees.
Therefore, if these particular specifications were used to compare with
the results obtained on a distributor testing machine, they would have to
be divided by two.