Clutch Question for the engine builders and others

[JoeWay]

I have spent a fair bit of time and money researching alternate clutch solutions for the Model A--see this link, for example. This research is prompted by the fact that good rebuilt Model A pressure plates, as well as good "V8" pressure plates with the counterweights, are getting harder to find.

I have identified a 9" diaphragm pressure plate from an older application which has the necessary large hole in the diaphragm fingers to clear the transmission input bearing retainer. This application has a very large installed base, so it is readily available new for a price about the same as the new so-called V8 (but actually tractor) pressure plates from the usual vendors. This pressure plate will be smooth, positive, and easy to operate.

The hitch (there's always a hitch) is that it is made for used with a friction disc about 0.070" thinner than the Model A/V8 disc. My clutch supplier says he can address this in two ways. The friction material can be removed from a new disc and replaced with thinner facing, or the pressure plate can be disassembled and machined/ground to accept a stock-thickness friction and then re-assembled.

Cost for a re-lined disc would be roughly double the cost of a new stock disc, or about $70. With this option the pressure plate could be used out of the box, but future disc replacements would have to be custom made again. Added cost=about $35.

Cost to modify the pressure plate would probably be around $50. The supplier has offered to do one plate without charge for the labor to get a price base and to validate the procedure. With this option the stock disc from any supplier, or the one already in your car or on your shelf, could be used. Added cost=about $50.

Which option makes the most sense to you?

I will share all the information about the part ID and supplier when we have figured out the best approach and have a setup that works, as I have with the Ford 10" clutch described in the link above.

Joe

 

[MikeK]

NEITHER. The pressure plate does not need to bolt directly to the flywheel! I shimmed plenty of P.P.'s for 'fat' friction disks when I used to waste money on SBC's. 0.070 spacers, either as individual washers, or a single punched ring (sort of looking like a rear banjo gasket) can be made from sheet steel to hold the pressure plate out the required amount. Then simply bolt it all together. The "fingers" will be 0.070 higher, but if you are already so close that the adjustment range is compromised, modifing the throwout bearing carrier length will be necessary, anyway.

 

[JoeWay]

Mike,

As so often happens, you have a simple but elegant answer.

Exact finger height is one of the questions yet to be resolved. It is very possible that selection of the correct shim thickness could also set the finger height.

Thanks.

Joe

 

[Milton]

V-8 STYLE PRESSURE PLATEFor Year(s): 28-31

V-8 PRESSURE PLATE - Helps reduce the amount of pressure needed to depress the clutch pedal by about 2/3rds. To use this, the crank must be counterbalanced and the flywheel must be machined. No changes in the way the clutch pedal is adjusted. NO EXCHANGE NEEDED. Uses the same clutch disk (11400) as the stock one.

Part #11460 V-8 STYLE PRESSURE PLATE $ 95.00


I found mine at Brattons. When he runs out I will ponder your question.

 

[JoeWay]

[
I found mine at Brattons. When he runs out I will ponder your question.

Milton,

Was the one you got the same as the illustration, with the flyweights? If so, was it new or rebuilt?

James Rogers and others have said new ones of this type are no longer available, and they value their cores at more than Bratton charges.

Joe

 

[john in illinois]

Joe,Thank you for your work on this. The rebuilt model A pressure plates are getting pretty beat up and a new diaphragm pressure plate seems like a good idea. I followed your discussion on this a while back.

John

 

[Milton]

Milton,

Was the one you got the same as the illustration, with the flyweights? If so, was it new or rebuilt?

James Rogers and others have said new ones of this type are no longer available, and they value their cores at more than Bratton charges.

Joe

Exactly as illustrated, with flyweights, and I purchased one last Oct. after looking at numerous tractor pressure plates being passed off as V8 plates. One guy on E-Bay even had his tractor plate pictured on top of an original FoMoCo 09A-7563 cardboard box. When I was shopping for mine Mac's came in second place at $84.95 + $40 core and I think it was sans flyweights.

As for new or rebuilt I would think that a rebuilt would command an exchange or a core charge. When I got it I couldn't tell and normally, if rebuilt, it will look too new although the one I got looked awfully good. But it matters not because the plate that I got works perfectly.

 

[Bill Stipe]

Joe while you have to machine the flywheel anyway I would machine a .070 recess on the flywheel that would be the least cost I would think.
And as long as we are talking pressure plates I tryed to find the LUK pressure plate you mentioned and none of the suppliers I talked to can match that number. what car or truck is this for and what year if I can ask.
I am looking for a better pressure plate for my alum flywheels on the 100 HP engines we are burning up the tractor ones when we race them at the FAST meets after about 4 passes. I found one for a 9.687 diameter on a chevy Camaro but they want to sell only the full kit with the disk and that has a 1-1/8 26 spline.

Thanks Bill

 

[Kurt in NJ]

I have seen a lot of cores go to scrap because the scrap dealer will pay more than the core dealer ---and the scrap dealer will load them himself, the core dealer wants them delivered.

Many of the cars with diaphram clutches that I have worked on have had choices depending on the type of throughout bearing ---a plate with flat fingers will use a to bearing with a rounded face surface, and the flat faced to bearings are used on plates with raised bumps on the ends of the diaphram fingers.

What is the pedal effort (lbs to push to floor) with the diaphram clutches you have used? On the V8 with the flyweight 9" it lists pedal pressure as 25lbs at idle, 60 lbs at 4000 rpm, I expect it would be about the same on the A except for the 4000 rpm.

At Hershey I saw a repro that looked like a tractor one that had flyweights welded to the levers ---my first though was --that will make a lot of noise when it comes off--

 

[CWPASADENA]

I would go to Ft Wayne Clutch in Ft Wayne, Indiana. They are a MAJOR rebuilder of vintage clutches as well as all the modern stuff. They are also old car people. I have bought from them for years and have found they do an excellent job and are very fairly priced. They have the correct springs so they are nice and soft like they are supposed to be. I used to send them cores but the last few early V-8 clutches I have gotten from them, they say forget the core, they have plenty.

I would watch a lot of the new stuff as a lot of it comes from China and I have heard a lot of horror stories about Chinese Clutches.

This is my experience and opinion,

Chris