Another discussion regarding spark advance. ( Later model Mallory Unit # 25275501 series)
Much has been said and done with the Mallory replacement distributor for the Flathead Ford. I think for a while these were shipped with a "chevrolet spark advance curve" a typical chevrolet small block engine usually has what i call a 12-14 degree curve or 24-28 degrees of advance in the mechanical part of the distributor.
Depending on the engine this may be too much for the Flathead .
The Flathead doesnt seem to like much over 22 degrees at approx 2500 rpm.
This unit is a new unit in the box a customer sent us to verify the flathead advance would be correct.
This unit is totally adjustable both for advance rate ( springs) and max advance ( stop).
After testing on the machine out of the box is looks like the advance is set for a max of 22 degrees but the spark curve has a large flat spot in it from 2000 to 2500 rpm. Red line on curve sheet. No amount of fuel service would ever fix this problem! The fix is to bend the low speed ( small spring) tab outward slightly and bend the high speed ( large spring) tab inward to get the desired curve.
A proper curve will show advance with every rpm change. Now the advance is all in at 22 engine degrees and 2500 rpm. Black line.
These units are very adjustable...