Model A

Ford Garage

Phillips Automatic Spark Control

This is an original Model A era accessory. It is an automatic spark advance mechanism to take the place of the distributor manual advance lever.

This unit is placed inside the valve chamber in place of the upper distributor shaft and has the effect of automatically changing the distributor spark timing position as a function of engine RPM, making the stock manual advance lever unnecessary.

This unit uses an imbalanced rotating ring which is gimbaled and aligns like a gyroscope as it spins. As the rotating ring aligns in the horizontal plane, a helix joint between the upper and lower shafts changes the relative angular position of the shafts, thus advancing the upper shaft relative to the lower shaft.

The geometry of the helix mechanically controls the maximum possible advance to about 30 crankshaft degrees, which is more than sufficient.

The stock Model A distributor had 40 crankshaft degrees of possible manual advance designed in, so that the initial timing could be retarded to 0 crankshaft degrees (TDC) for enabling starting with hand cranking, cold weather, and poor fuels.

The Nu-Rex centrifugal advance unit is a reproduction copy of the original era accessory Phillips Automatic Spark Control. Click the link to see the advance curve data from the distributor test machine.

July 2005