The following pics illustrate the differences between the Model A and B and later V8 Ford pressure plates. Also shown are the clutch disc and pressure plate adjustment instructions.
Pictured above is the 15 pound pressure plate used on 1928-35 Ford cars and light trucks.
Ford instructions for adjusting the pressure plate used on 1928-35 Fords.
The 2.5 pound nine inch clutch disc used on 1928-42 Fords. The first ones in the Model A era had spoked hubs and did not have spring loaded centers.
Pictured above is a Model A/B flywheel which has been cut down by Bill Stipe to 37 pounds. It uses the V8 pressure plate which Ford introduced in 1935 and which is centrifugally flyweighted.
Shown below is the inside of Bill's flywheel lightened for use with the later V8 style pressure plates.
Pictured above and below is the 1935-42 V8 Ford 09A-7563 pressure plate used for updating Model A's and B's. This is the desirable pressure plate which has the adjustable fingers and centrifugal flyweights which enhance high-speed, low-effort operation.
The 'weighted' V8 pressure plate shown above has three outer flyweights which exert leverage and increase pressure on the disc as the rpm is increased, but allow for lighter spring force, lower pedal force, and easy clutch disengagement at low rpms. A desirable feature for a car!
The pressure plate shown above is the stiffer and inferior 8N-7563 tractor pressure plate typically sold by many Model A parts dealers and rebuilders.
The whole point of converting to a V8 style pressure plate is primarily to get a reduction in the pedal effort for comfort and easier operation. Unfortunately, most of the parts vendors today offer the 8N-7563 pressure plate, which was designed for the 8N series Ford tractor.
Although the 8N tractor pressure plate can be fitted and will work, it is a poor second choice. It is a heavy pressure plate with high spring forces, no centrifugal flyweights, and non-adjustable release fingers. It was intended for use in power transmission on a tractor, not high-speed low-effort operation on a car.
The Ford 8N tractor pressure plate does not really offer much (any?) driving or pedal improvement or net weight savings compared to a stock Model A pressure plate.
For lower pedal effort, the preferred pressure plate is the Ford V8 car 48-7563 or 09A-7563 pressure plate with flyweights, which were used on 1935-42 Ford cars. These are both 9 inch size, and are also lighter weight than the 8N tractor pressure plate.
Follow the Ford Garage link below to read more about various Model A and B stock and lightened flywheels.