Clutch / Torque Converter: What size clutch disc?

[Studejohnn]

I need some advice on the clutch disc on my 289 with a t85 behind it. The clutch wasn’t disengaging, grinding gears. Took it all apart today, and the problem is mismatched parts. Pressure plate measures 10” across the clamping face, nine springs, B&B, 3 fingers. Disc measures 10.5 inches diameter. Guy gave me the wrong disc, but I was as much a bonehead because I didn’t check before putting it together.
I see a 10” disc is available, but I also see a 9 1/4” disc for sale by some of the vendors. I want the 10”, correct?

[55coupe]

Yes 10 . I used the 9 1/2 in my car with the same setup as yours it’s not enough clutch for a 289. If I go back into my car I’ll use a 10 1/2.

[StudeRich]

A 289 gets a 10 1/2 Inch Disc and Plate. All of the above are for 259 Engines. You have the wrong Pressure Plate.

A Clutch Rebuilding Shop is THE Place to go, not some "no nothing" Auto Parts Store that sells NEW Chinese "Zoom" Brand!

[Studejohnn]

Well, I have the 10.5” disc. Looks like he gave me the right disc and the wrong PP. i recall we were trying to cobble together a clutch because the engine didn’t have one at the time I bought it. Just an honest mistake.
I would like to stay with the PP I have since it was bolted on and used at the machine shop during engine balancing. Anyone see any problem with going with the 10” disc and PP (for 259 engines) behind a 289 (going into a ‘55 half ton and, at my age, will probably never see 3,000 rpm)

[StudeRich]

I need some advice on the clutch disc on my 289 with a t85 behind it. The clutch wasn’t disengaging, grinding gears. Took it all apart today, and the problem is mismatched parts. Pressure plate measures 10” across the clamping face, nine springs, B&B, 3 fingers. Disc measures 10.5 inches diameter. Guy gave me the wrong disc, but I was as much a bonehead because I didn’t check before putting it together.
I see a 10” disc is available, but I also see a 9 1/4” disc for sale by some of the vendors. I want the 10”, correct?

According to this you have the wrong Pressure Plate for a 289.
Many 289 Trucks and Avantis used a stronger P/P with all 12 Springs, filling all 12 Holes.

The weight of a Truck and it's possible Load, is enough to cause premature wear on the Disc.
My 1 Ton 289 Transtar has a Factory 12 Inch Clutch, I had the Rebuilder bump the P/P up to 3150 Lbs.

Note that Pressure Plates and Flywheels are not balanced to the Engine Assy. only within themselves, so it's easy to have the correct one Balanced.

[Studejohnn]

Thanks Rich and all. Checking around, I’m seeing around $250 big ones for a 10.5” PP plus a core charge around $75. Pretty steep, especially when I don’t have the correct one toget back the core charge. There would be a bit more to have flywheel and PP balanced again. If I stay away from yanking tree stumps, I should be o.k. with the 10” setup.

[Buzzard]

Hi John,
Good to hear you again.
Although not Studebaker, in my '70 Avanti II with a very strong, heavily modified 355 CID, I used a McLeod 11" Borg & Beck in a two piece Lakewood Scatter shield and am working on their hydraulic throw out bearing with a Doug Nash 4+1 transmission.
I will keep you posted. I don't recall where but somewhere I read to use the largest possible clutch diameter you could fit.
Good luck on yours.
Bill

[PackardV8]

I don't recall where but somewhere I read to use the largest possible clutch diameter you could fit. Bill

Yes, Bill, the largest diameter clutch disc and pressure plate have more clamping area and can hold more force with less spring pressure. They'll also wear longer.

No, the larger diameter disc and pressure plate is a bad thing for fast shifting. The larger disc has more inertia and requires more effort from the synchros to match RPM on shifts. If it is shifted fast, the synchros will have to be replaced more often. That's why modern clutches are smaller diameter with twin discs; same area, less inertia.

Maybe, have a reason for choosing the diameter and the spring pressure.

jack vines

[StudeRich]

Thanks Rich and all. Checking around, I’m seeing around $250 big ones for a 10.5” PP plus a core charge around $75. Pretty steep, especially when I don’t have the correct one to get back the core charge. There would be a bit more to have flywheel and PP balanced again. If I stay away from yanking tree stumps, I should be o.k. with the 10” setup.

You could ask someone here for a Core Stock 289 10 1/2 " Pressure Plate if you don't have the Original Old one.

I hope you are buying directly from a Clutch RE-BUILDER! Today's New ones or from 2nd Party unknown re-builders are very often junk.

The Flywheel will not need re-balancing as it like the P/P, is Internally Balanced alone.
Only the Crankshaft Counterweights and Assy. vs the Rod and Piston Assembly is balanced as a Set.

[Buzzard]

Edit my post #7
My memory started to kick in and I was wrong in post#7.
I now recall I had the flywheel re-drilled and I measured and it is a 12" McLeod Borg & Beck LONG clutch assembly. Damn I hope this project gets finished soon as my memory is not helping at all. And yes I had the assembly zero balanced.
Bill

[Studejohnn]

I can see why Studebaker called for an 11” clutch for the trucks since they are work vehicles that might get called on to tow or carry a heavy load. I won’t be using this truck that way. If a 10” was acceptable behind a 259, then it should be o.k. Behind a (bored out) 289. Again,as long as the duty is light.
Fast shifting aside, I do hope to arrive at smooth shifting. To get there, I fabed a bracket for the Indy shifter I picked up at a swap meet and modeled it on Jack’s shifter over on Bob’s resource page. I doubt the Indy will be fast, but if I get smooth, positive shifts out of the T85, I’ll be happy with that. Build as you drive, I heard that around here once or twice.
Yes, I did find a suitable disc from one of our Studebaker vendors.

[jackb]

If you go to the 11 incher expect building up a good strong left leg muscle group. A real bitsh in traffic even with 2nd /OD..... I agree with recommending a good (big metro area) clutch rebuilder. I kept the 11 inch PP but had the old timer downgrade the spring pressure since I was seldom towing or carrying heavy loads. Also, if you go big, make sure your clutch linkages are all in great condition. What caused some of my decision was a broken lever and tired and seriously grooved pivot pins & collars......

[Studejohnn]

Right. PP is over to a clutch rebuilder in Salem right now. They’ll check it for warping on the clamping face and the body itself. I fairly certain one of the fingers is an 1/8 or so lower than the other two. So they’ll check that.
First thing I looked at was the linkage, hoping that’s where the problem was. I had put a new support bearing inside the frame. The rest of it, shaft, collar, pins and fork, all looked good.

[JoeHall]

If possible use a 10.5" disc, but look in the parts manual and go with the lightest duty PP called for behind a 259. That will give you plenty of grip for your intended use. Ignore those who advise a heavy duty PP, as all that will do is make the clutch pedal harder to push, and put needless stress on related linkage. Despite you stating your intended use clearly, it seems there's a reading comprehension problem, as some would have you setting your truck up for drag racing or hauling gravel.

Look in the archives here, there's lotsa info on the various PPs and discs available, and parts numbers. I am too lazy to look it all up again. But again, go with the LIGHTEST duty PP, and ignore anyone who tells you different. For your stated, intended use, a light duty PP will fill your needs just fine. But use a 10.5 disc, if possible.

[jackb]

Last time I called NAPA on a PP there was an original new one in OH.....