distributor change

[German guy]

Looking at a 12V neg ground conversion coupled with modern centrifugal advance distributor. Any advice out there on the relative merits of the standard FS distributor and the "Zipper"? Obviously the "Zipper" looks very much like the original...so that is a plus....at a 150$ price increase. Any difference in performance between the two? Any advantages to ignition wires rather than the eccentric looking naked brass connectors?

[nkaminar]

I will comment on the naked brass connectors. At the time the Model A was designed, radio frequency emissions were not considered. Because of the high frequency of the spark the brass connectors, or solid ignition wires, can generate radio waves that reduce the amount of energy available at the spark plugs. The resistance of the graphite core wires actually increase the energy at the spark plugs because they reduce the radio emissions. However the graphite wires can wear out and must be replaced as part of the maintenance. The naked brass connectors are there for the life of the car, and because they are so short, the loss of power to the plugs is minimal. Your best bet is to replace the high tension wire from the coil to the distributor with the modern graphite wire.

[CT Jack]

I see no advantage in converting to 12V negative ground setup if you plan on using an FS distributor. I have been using the FS "Zipper" distributor with a standard 6V positive ground for more than 10 years. The FS distributor uses a slightly higher output coil compared to the stock coil. The stock Model A coil resistance is 1.2-1.4 ohms with an output of 12K-18KVolts. The FS system uses a different coil which has a resistance of 1.5ohms and a 40KVolt output. The "Zippers" range of centrifugal advance for a stock head is 24-26 degrees @ 2,000rpms. (for stock heads and 5.5:1 compression ratios).
The advance setting for high compression heads (6:1 or higher) is supplied at a range of 16-18 degrees.
The advantage of the centrifugal advance is that you never have to manually adjust your advance/retard settings. This makes driving a Model A much more enjoyable experience. The ignition settings are always set automatically and exact. No more adjusting points and manually advancing the distributor when approaching inclines.

[AL in NY]

I have been running the Zipper since it came out in 2008-09 and love it. No problems at all with the distributor. Be sure to wire it exactly as instructed by FS and inform them of our engine's compression ratio and any other performance enhancements so they can tailor the distributor with the correct advance curve.

[Synchro909]

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Originally Posted by AL in NY

I have been running the Zipper since it came out in 2008-09 and love it. No problems at all with the distributor. Be sure to wire it exactly as instructed by FS and inform them of our engine's compression ratio and any other performance enhancements so they can tailor the distributor with the correct advance curve.

I agree, Al. The maximum advance allowed decreases as the compression ratio rises and the curve changes with CR and cam shaft specs.