Pressure plate differences

Can anybody tell me, if any, how much is the difference in pressure to actuate a early Ford long style 3 finger pressure plate opposed to a Chevy diaphram pressure plate?
Thanks

 

There are many variables that make it hard answering your question accurately, as there were/are several applications of Long and diaphragm pressure plates. But, as a general rule, both will feel about the same initially. The diaphragm pedal force, however, will decrease as the plate disengages, while the Long (and B&B) pedal forces will increase during clutch disengagement. This, along with far fewer parts, have made the diaphragm the OE/street/performance clutch of choice for over 30 years.

 

A long style will have a flat faced through out bearing and the diaphragm will be curved

 

Also, they're not the same bolt pattern, and so are not interchangeable.

 

There are several diaphragm pressure plates available today that are direct replacement for Long p-plates, with the same bolt pattern.

 

Please give an example of ANY diaphram pressure plate with three groups of two mounting holes...Only diaphram pressure plates I have seen in my 80 years on this earth are 6 evenly spaced mounting holes...Plus,there is a big difference in finger length on them for different size T.O brgs.

 

I first saw the diaphragm p-plates with Long bolt patterns at our local clutch re-builder several years ago, and then found out they are available from NAPA for certain FoMoCo applications. Honest!
There are basically two diaphragm finger styles, straight for large T/O bearings, and bent for smaller bearings.

 

Thanks V8 Bob,,,,,I still have never seen one...My NAPA man hasnt either.and he is a hotrodder

 

Yeah, I've seen those pressure plates too....was told by a counterman that the manufacturers are going to all diaphragm clutches. Just adapting the long style bolt pattern to them.

 

Thanks for your replies,I am using a chevy diaphram pressure plate and have modified a bell housing to suit a early ford clutch fork with a cross shaft and lever actuation as per early fords..

 

As for pedal effort, I have cars with both styles and never really noticed much difference. I suppose it depends on your linkage setup and pedal ratio too...

 

You fail to say what T.O brg you are using,,,if its one for a 1 3/8-10 spline..Chev pressure plate is incorrect as they are for smaller dia T O brgs Chev was 1 1/8-10 spline..fingers on Chev pp are too long for use with 1 3/8 T O brg

 

http://www.ramclutches.com/Tech/perf_tech.htm#APPLICATION AND PRODUCT VERIFICATION

" I want to use a diaphragm pressure plate instead of a lever style. What pressure plates share common bolt patterns?

For GM or Chrysler applications, Borg and Beck lever style and diaphragm pressure plates will interchange. So if you have a 10.5 or 11 inch Borg & Beck, you can use a 10.5 or 11 inch GM diaphragm pressure plate. In early Ford applications, the 10 and 10.5 inch long style covers have a diaphragm subs***ute in 10 inch that may be used, although holding power will suffer by making this move. 11.5/12” Ford lever style clutches have a diaphragm subs***ute available. Please see the RAM applications for further information. "

 

The 60's Chevy and Olds (maybe Buick) diaphragm pressure plates will fit the B&B bolt pattern.

This is what Studebaker used, a 10.5 B&B w/rollers. (Rollers wedge between the fingers and cover to add clamping force and required much extra pedal pressure to shift at high rpm. This is the worst rpm shifting PP there is.)

The Ford is superior for RPM increased pressure because centrifugal weights are built into the forged fingers - no extra effort "unwedging" those rollers.

The Ford was made with B&B mounting holes so the GM guys could use them.

Both cover styles of GM diaphragm will bolt to Studebaker which is B&B.

There are 2 cover styles: Chevy which has a "rectangular" side profile and the Olds (might be Buick, I forget) which has a "t****zoidal" side profile.

RE: Studebaker V8 Application:
The T****zoidal cover has less clearance issues and can be used in an OE bell housing with some minor grinding on one feature that appears in 2 places.
The Rectangular cover requires about another .150" addition axial clearance. (I inadvertently used the cover with a custom Stude Weber Steel wheel that unknown to me, had been made .150" thinner than OE - there by providing more clearance. I discovered this when I installed a Fidenza Aluminum flywheel and the engine was locked. So I went to the Trap cover which had more clearances.

RE: Diaphragm Clutches:
Because of their "snap action", they engage more abruptly, and can break things.

 

Not always. It depends on the shape of the fingers on the diaphragm.

Those can be flat, or curved.