MTFCA Forum

What is the difference between a early clutch disc drum and a later 1919 -1927 clutch disc drum????
The vendors list both.

The early one needs a thicker spacer plate to go in first to prevent the clutch plate from slipping between the brake drum and the hub.

Actually the most important difference is the distance between the thrust surface and the set screw location. Trent Boggess posted the differences here on the forum many years ago. This change was, as I recall to account for the change from the flanged braked drum bushing to the three steel thrust washers. The difference was identified on the clutch hub by the presence of the the Ford logo or the absence of it.

Here is text from Trent's original posting:

https://www.mtfca.com/phpBB3/viewtopic. ... ub#p219046


"One additional point: there are two versions of the Ford script clutch disc drum. The early version has Ford script on the FRONT side of the drum and was used with the top hat brake drum bushing. The later style can be identified by having Ford script on the REAR side of the drum. This is the one used with the three steel spacer washers.

The early style drum with the Ford script on the front side is not very common, but does exist (along with a couple of other variations as Ford tried to solve the clutch disc drum/top hat bushing issue). Be sure to used the later style with the Ford script on the rear side of the drum when using the three steel washers.

Respectfully submitted,

Trent Boggess"

The distance from the set screw to the thrust face is the difference.

Early with top hat bronze bushing uses a clutch drum with a .515 distance. 33/64”

Later is .531 or 17/32”

Why the odd numbers? Seem to be a Henry’s favorite thing. LOL

I have found over the years that most dimensions on Ford parts are almost without exception, fractional inch increments, including 64ths. This seems to be the case with Model A parts as well.