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The function of the 1957 distributor differs from the '55 and '56 models in that the 57 model has centrifugal and vacuum advance. The construction of the '57 model is also different. The housing is taller to accommodate the centrifugal weights and springs. The description and operation of the '57 distributor is well covered starting on page 2-16 of the 1957 shop manual and the specifications are on page 2-23. The 1957 points plate has ball bearings around the outer edge and should be checked to insure it is free to rotate freely in both directions. If the points plate is frozen the engine timing will not advance beyond its initial setting and the engine will over heat. In numerous cases an overheating condition is treated with a new heavy duty radiator, multi blade fans and numerous other remedies and the problem is in the distributor.
The timing must be checked and adjusted three places when doing a tune up on a 1957 model. First check the initial timing and adjust to 3-degrees BTC for std. and O.D. transmissions and 6-degrees BTC for automatic transmissions.Second check the centrifugal advance with the vacuum advance disconnected. The timing should advance beyond the initial pre set timing an additional 12 1/4 to 13 1/4 degrees @ 2000 RPM. If the centrifugal advance is not within those specifications it should be adjusted in accordance with the instruction on page 2 -10 of the shop manual. The third item to check is the vacuum advance mechanism. Connect the vacuum source from the carburetor to the vacuum advance mechanism. Accelerate the engine, @ 1000 rpm the timing should advance an additional 11-13 degrees. Total advance includes initial, centrifugal and vacuum for approximately 32 degrees. This procedure is best done with the distributor removed from the engine and installed in a distributor machine. It can be done installed in the engine with the type of timing light previously described. If it is done on the engine keep in mind that the centrifugal advance is also working when the engine is being accelerated to check the vacuum advance. Page 2-17 of the 1957 shop manual describes the operation of the vacuum advance mechanism.