Crankshaft Vibration Damper

Ford crankshaft vibration dampers (also known as harmonic balancers) are identified by basic part number 6316. A damper is a heavy, circular device mounted on the snout of the crankshaft to help counter torsional and resonance vibrations from the crankshaft. OEM dampers are constructed of a cast iron hub and a steel outer timing ring with a layer of vulcanized rubber between the hub and ring. The hub is keyed for proper location when mounting on a crank, ensuring that the timing marks present on the ring line up where they're supposed to be. The front of the hub has three mounting holes to secure the crankshaft pulley. The correct original color is semi-gloss black.

The 428 CJ and 428 SCJ used different neutral-balanced dampers, each of which can be identified by the engineering number found on the hub. When compared side-by-side, the SCJ damper is obviously wider and thicker than the CJ damper. Thanks to Jim Kruse for letting me borrow his SCJ damper for these pictures.

Dampers front view

Front view of 428 SCJ damper (left) and 428 CJ damper (right)

Balancers front view

Rear view of 428 SCJ damper (left) and 428 CJ damper (right)

Application Chart

Engine Engineering Number Service Part Number Outside Diameter Thickness
428 CJ C8AE-A1, A2 C8AZ-6316-B 7" 1.125"
428 SCJ C8AE-C C8AZ-6316-C 7.5" 1.5"

Note the two engineering numbers associated with the CJ damper. It appears that both dampers were factory installed, and we've been unable to find any documentation or references that explain which damper would be installed. The A2 damper is slightly heavier (6.9 lbs. vs. 6.3 lbs.) and has a thicker (0.75" vs. 0.55") outer ring as compared to the A1 damper. They both have the same 7" outside diameter. The timing ring difference has led some to believe that the A2 damper is the "correct" one for a 428 CJ, but we have multiple reports from owners of original cars that have date-code correct A1 dampers installed. Similarly, we have multiple reports from owners of original cars that have date-code correct A2 dampers installed. Note that the same damper was used on 390s and non-CJ 428 engines, so they're fairly easy to find.

A1 A2 Damper Comparison

A1 damper (left) compared to A2 damper (image courtesy of Kerry Wortman)

The timing ring on the 428 CJ damper has timing marks from 10 degrees after top-dead center (ATC) to 30 degrees before top-dead center (BTC). The SCJ damper has timing marks from 10 degrees ATC to 46 degrees BTC. A letter-digit date code, such as "B8" for February 1968 or "K8" for October 1968, is present just to the right of the "BTC" mark on the A1 damper and the SCJ damper. The date code appears to the left of the ATC mark on the A2 damper. The thickness of the timing ring and the location of the date code make it easier to identify the damper without explicitly seeing the engineering number.

A1 Date Code

A1 Damper Date Code

A2 Date Code

A2 Damper Date Code

If you have an original damper that you'd just hate to toss, know that they can be rebuilt and made better than new! See the registry forum (registration required) for details.

Images Provided by Members and Friends

Thanks to Bill Upham of Mansfield Restoration Parts for these images:

C8AE-A1 CJ engineering number detail
C8AE-A2 CJ engineering number detail

Thanks to Jim Kruse for the damper loan that allowed me to take this picture:

C8AE-C SCJ engineering number detail