Technical Who has a flathead Ford with an 11" clutch?

That I did. It's what was in the car when I bought it and didn't know what it was. It's in a 41 Ford Coupe with the 8 cm Merc Flathead and the stock 41 trans. The clutch was "fine"with the stock pedal ratio and everything but once I put the 10 inch clutch in it's like it's not even there. The only reason I put the 10" in is because I figured that's what was in there and had already bought one anticipating the motor swap and didn't figure somebody would put the 11-in truck clutch in there. For a hot rod I figure a 11 inch clutch maybe Overkill unless you had something with a lot of power and we're dumping the clutch

 

Years ago I had a '40 1 1/2 ton cab and chassis with an 8ba and 11 inch clutch. I don't remember the clutch being any more difficult that the 9 1/2 plate in my '39 p/u. And I'm an old fart compared to a youngster like you. If it were me I'd run the 11 incher. But that's JMO.

 

I have my 47 ford coupe, mild 59a 11Inch clutch with stock 47 trans, it is not hard to push, no problem in traffic for 13 years, only issue if you consider going T5 pressure plate s too big for adapter.

 

No thank you on an 11" clutch. Too stiff for me.

Dave

 

My '52 F-1 pu has an 11" clutch. It is the easiest to operate clutch of the 5 rigs I own with clutches.
Not sure why, but I believe it has to do with the linkage design.

 

I have an 11" clutch in my A-V8 with hydraulic slave cylinder. It is not hard to push at all and I'm an old fart, too. The one important thing to do if you want a nice, smooth engine with no vibration is to take the flywheel, clutch disc and pressure plate, all bolted together, to a good machine shop and have it balanced as an assembly and reference marked. There's a lot more centrifugal force at work here than with the standard 9" clutch. Balancing should be done with any clutch change. It does make a difference. The 11" disc will last a lot longer than the 9", too. Be sure to check for pressure plate clearance at the top of the bell housing. Some passenger car housings have thicker metal around the little inspection plate and the 11" pressure plate will hit it and just stop right there. That area must be ground down for clearance. You probably don't want to find that out after everything is put together. Check carefully.

 

If you have it , run it.

 

The trucks we had seemed fine.
But I’ve never driven one with the small clutch either.

 

IF it's too stuff you can mess with the springs. Talk to Fort Wayne Clutch.
https://fortwayneclutch.com/

 

I would think the linkage system on trucks have a little more leverage than the linkage for a car.

 

The larger diameter clutch is more prone to chatter, and a 10" will do the job.

 

I think he has seen what your describing at the end of your post all too well.

 

Am running one in my 34 pickup.
I had a pressure plate rebuilt with springs that were not as stiff as stock.
No problems at all. Don’t know if the weaker springs helped but I thought it was a good idea while it was being rebuilt. I’d run it.

 

11 inch was for trucks. Lots of rotating mass. Big waste of energy in a hot rod.
A 9 inch will have normal "feel" with stock linkage even if it has been modified with stronger springs.
A new STOCK 9 inch will handle 300 hp.
The engine will spool up NOTICABLY faster with a 9 inch. Makes street driving more pleasant.
A 9 inch will outlast the rest of the engine.

 

TRUTH, I was wondering when someone was going to mention this.
Tom

 

Just a question, are the flywheels the same for an 11 in clutch and a 9 inch? If so, then how much difference in weight between the two pressure plates and discs?

 

Ran a Scheifer 11" in my flathead dragster. Don't think you need anything that big unless you have a very
modified engine and are racing.

 

A 9 inch clutch is all you will need for your project. They work just fine. I have used them for 221 , and 239:motors with no problems what so ever. Also have used them when running a small block 265 or 283 hooked up to 39 trans.

 

The fly wheels are all the same. 11 in pressure plate weighs about 17 lbs. 10 in about 15 lbs. 9.5 in about 12 lbs.

 

You obviously can run what you have, or you can decide that now is a good time to go to a smaller diameter clutch with whatever spring weight you want. As Pete noted, you'll rev a lot faster with less reciprocating weight.

I've had RAM clutches build me custom clutches (and lightened billet steel flywheels) with whatever clamping force I want/need. I usually have them build 10" clutches - but that is just me. They can get the steel flywheels down to about 24 lbs - with lightening and scalloping around the pressure plate area.

One thing on Ft. Wayne - they used to do a decent job of refurbishing pressure plates and supplying good quality rebuilt ones. I've heard that they no longer do this type of work - they just source/sell the same offshore crap that others have. I can't confirm this (as I don't use their clutches on my builds) - just a word of caution.

One thing to note is that some 11" clutches will interfere with the transmission bell-housing section - especially early V8 cases. The counterweights can drag on the case. So, check everything BEFORE you do your final assembly and attempt to install the engine.

 

They are dimensionally similar (32 - 48), though obviously the flywheel has to be drilled and balanced for the specific clutch you are using. Early flywheels typically have a big outer ring of material on them - that performance guys usually shaved off.

 

Overkill with a mild FH in a light car. 10 inch is good. I've even had a few customers do a 9 inch with the right springs and they seem to be doing fine.

 

The late greats Bruce lancaster , and rumble seat both said the lightest ford clutch and flywheel set up was the Ford 9" with an early flywheel that has the big weight blob around the outside cut off to make it a flat surface. Thats whats in my avatar car, with a new pressure plate from FT Wayne back when they were made in house. Mine, however, will slip at low rpms if I floor it. I've not taken it apart yet, but I suspect I will find springs that are not up to spec as it seems many folks claim the 9" will hold fine with a mild engine like mine, a 59a with merc guts and single carb.
It does spool up very quick, and decelerates quickly too. I like it...need to fix it !

 

Here is a picture of a recently purchased flywheel from RAM (custom designed) - will install it in the coming weeks:

 

Fuck that 11” clutch. I’ve tried them on the street in a fender less 34 coupe and in my blown 34 coupe that’s a track only car. My new setup street or strip is a 9.5” pressure plate on a 9” disc. All off the shelf stuff and even with a blown flathead on slicks with a locked rear the clutch doesn’t slip. It’s seriously like 2/3 the weight of an 11”

 

So, what is the f.h. original flywheel weight?

 

If you have the brand and part numbers, that would be helpful to a lot of folks. I agree with you on the fact there is absolutely no need for a 11" truck clutch . . .

 

I would think the PP spring rate , lever configuration ,the pedal ratio soul determine the pedal pressure & not the diameter of the clutch