428 Cobra Jet and Super Cobra Jet distributor assemblies are identified by basic part number 12127. Identification information, including the casting number and date code, can be found on the distributor housing. Here's one example, a 1970 D0ZF-12127-C distributor for engines mated to a manual transmission with a 9J26 (September 26, 1969) date code:
| Transmission Type | 1968 | 1969 | 1970 |
|---|---|---|---|
| Manual | C8OF-D | C8OF-H | D0ZF-C |
| Automatic | C7OF-F | C8OF-J | D0ZF-G |
The 1970 D0ZF-C (manual transmission) distributor is a dual point unit. All of the others are single point units. According to the 1970 service manual, "Two sets of pivoted breaker points are used because a slightly longer dwell is thus possible. This results in a better high tension spark". If you'd rather not deal with points at all, these distributors take Pertronix electronic ignition conversions quite well. Though not concours-correct (two wires leave the distributor instead of one), the Pertronix unit makes a huge difference in drivability and maintenance ease for cars that are driven frequently. See your favorite vendor for pricing information.
1970 dual point breaker plate
All of these distributors are equipped with both vacuum and centrifugal advance units. Dual diaphragm vacuum advance units (found on C8OF-D, C8OF-H, and D0ZF-C) use carburetor vacuum on the outer, primary diaphragm to adjust ignition timing in response to engine speed and manifold vacuum on the inner, secondary diaphragm to retard timing during periods of closed throttle idle (to reduce emissions). Single diaphragm vacuum advance units respond only to carburetor vacuum.
Vacuum Advance Part Numbers
| Transmission Type | 1968 | 1969 | 1970 |
|---|---|---|---|
| Manual | C8AZ-12370-A | C8AZ-12370-A | C9ZZ-12370-A D0ZZ-12370-A |
| Automatic | C5AZ-12370-A | C5AZ-12370-A | C5AZ-12370-A |
Note that the advance unit used for 1970 models with manual transmission used two different hose connectors for the outer port. Up through the end of October 1969, the unit came equipped with a screw-in hose connector. From November 1969 through the end of the model year the unit came equipped with a press-in hose connector. This same unit was also used during the 1971 model year on Boss 351s and 429 CJs and SCJs with manual transmissions, but a cast-in hose connector was used. The 1968-1969 manual transmission unit has an 9/16" wide silverish band and the 1970 units have an 11/16" wide goldish band.
© 2008 Scott A. Hollenbeck. All Rights Reserved.
