Technical Help: Diaphragm Clutch with 327 SBC + '39 Trans

I'm building a '35 5W coupe with a 327 Chevy motor, '39 trans and a '40 banjo. I've rebuilt all three components. With our tourist town traffic (and my advancing age) I opted for a diaphragm pressure plate set-up. After research I opted for the pressure plate and clutch disk from RAM Clutches. Mike Norcia at RAM has been very responsive and helpful -- but we haven't solved the problem.

The stock Ford clutch release rod, even with the clevis threaded all the way out (to a point I felt was unsafe) put the clutch release point right on the floor. I found a clevis that was almost an inch longer. I had to machine and press in some bushings to accept the Ford release arm pin -- but that was far easier than dicking around with lengthening the clutch arm.



This worked (everything shifted smoothly first to second to third, back to reverse) so I know there's no issues INSIDE the tranny -- but the release point was still at the floor. After a couple of trips around the block I could no longer get it into first or reverse.

I pulled this throw-out arm as far forward towards the diaphragm fingers as I could by hand before installing the longer clevis. To get any more length for the clutch rod/clevis I’m going to have to figure out some mechanical way to rotate that throw-out arm even farther forward. But I’m afraid at that point the face of the throw-out bearing will be up against the diaphragm.

Is anyone familiar with this set-up? Thanks.

 

IIRC the go to clutch in those set ups was a Merc finger piece but admittedly it has been too many years for me to be certain. I am sure others will recall and chime in.

 

Here is a good read about the Merc clutch. Might find your answer there
Technical - Borg and Beck Pressure Plate ID | The H.A.M.B. (jalopyjournal.com)

 

Do you have a "high" cone or a "low " cone diaphram clutch ?
A high cone clutch is needed.

 

There is a long and short throw out bearing available. I'm thinking you're going to need the long style bearing. From your picture, it looks like you have a short TOB. The fork is RIGHT behind the bearing. The long TOB (at least in the old days, could be redesigned by now) basically had a cast iron body with the bearing pressed on the end. The fork sits about an inch behind the bearing. I'm pretty sure that the long bearing goes with the "flat" pressure plate and the short bearing goes with the tall pressure plate.

PS grew up in Capitola!

 

what pedal assembly & what clutch arm are you using?
A '39 pedal assembly & a '39 clutch arm should do the trick.

 

Hey Pete — I’m using my ‘35 pedals and clutch rod along with Richard Lacy’s juice brake conversion set-up (the bell-crank version that tucks up tight inside the chassis). Driver’s side exhaust manifold came from you awhile back via Jim Cocores — thanks. I wasn’t aware of the different throw-out bearings Michael Cruz mentions above. That might get me the extra travel I need.

 

Cruz, please explain what these different length throwout bearings came on? I've never noticed different length bearings or cast guides.

 

Been selling early Ford trans kits for 30 years and never seen a long early Ford large TO bearing. I thought they only made one size. For a high crown PP you need something like a CA30. I just got one from Fort Wayne Clutch, custom made.

 

What’s a CA30?

 

After reading through this I also believe the diaphram pressure plate is not correct for the application. By over centering the clutch fork you are loosing mechanical advantage. Either a high cone pressure plate is needed or some special TO bearing is needed , which not speaking fluent flathead , I don't know if it is available. On all the Chevy stuff I have built the fork needs to come out of the bellhousing at a 90 degree angle or preferably less than. This was always done by adjusting the fork with an adjustable pivot or a longer TO bearing. Which once again not sure is available for a flatty. Hopefully someone will have the answer BTW beautiful car.

 

Here are photos of the Ram pressure plate and clutch disk. Is this a “high crown” or “low crown?” Yes, I surfaced the flywheel before assembling everything.

 

I looked this up in my Green Bible and Ford used the same 78-7580-A Throw-Out Bearing from 1928 to 1948.... are these Ford bearings you're referring to?

 

That is a high cone diaphram pressure plate.

 

This is what I used in my 283 to 1941 box. It's a Merc pressure plate to a SBC flywheel with the correct bolt spacing.



I took the picture for my own reference later. It worked great!

 

I may have a long thrw out bearing . If I can find it . Ive been keeping it because Ive never seen one . This would of come off a 394 old mated to a flathead or a 47 ford panel ( x military ambulance) with 4 speed and pto.

 

Thanks, that’s my adventure. Expensive, but proven.
Haven’t installed it yet, still have to gasket and paint my engine.
FWIW, a friend tried that Ram diaphragm setup on his 327/39 box and never could get it to work right. Went with Ft. Wayne. Your results may vary.

 

Does that B&B pressure plate use an early 50's Merc TO bearing with spring clips that go over the fork?

 

Detonator: My CA30 looks just like your RAM diaphragm PP but has the bolt pattern like the early Ford PP.

 

The 78- prefix on the part number for the Ford throwout bearing indicates a part first used on '37 Ford cars ('37 pickups used the same one), but the Green Book lists it as replacement back to '28. Ford often re-designed a part so that it would interchange with an earlier design part. So there is some difference between a Model A TOB and the design first used in '37, but they are interchangeable. Off the top of my head I don't know what the difference is. The transmission case that first appeared on '37 85 HP cars was supplied as a replacement back to '32--the guts from a '32 transmission will fit in it, and the '32 shifter top will bolt on,

 

All done and dialed in. Thanks for all the response. Now to put some miles on ‘er.

 

So what combination of parts did you wind up using? Ram pressure plate with which throw out bearing? ‘49- early ‘51 Merc Borg & Beck pressure plate?

 

Ram 401 pressure plate, Ram 212 clutch disk and stock Ford throwout bearing. The longer clevis gave me the additional travel I needed to reach the diaphragm fingers. I had to tear out all the floorboards again to get to the inspection port in the bell housing and with a buddy on top sliding the bearing and me underneath adjusting the rod length — and several runs around the block — we were finally able to dial it in. I’m running steady rods so it’s all smooth with no clutch chatter.

 

Here is a few pics of a long throw out bearing. I think it came off of a stationary motor with what I call a in/ out box . I was told it was used in a grain elevator.