Stock crankshaft/V/8 clutch

marc silva

marc silva

Senior Member
Just wondering why is it that everything I have read says that you can only use the V/8 clutch with a counter weighted crank shaft? I would think that if the flywheel and clutch were balanced that it would work on the stock crankshaft.

As always, your knowledge is appreciated.
 
marc silva said:
Just wondering why is it that everything I have read says that you can only use the V/8 clutch with a counter weighted crank shaft? I would think that if the flywheel and clutch were balanced that it would work on the stock crankshaft.

As always, your knowledge is appreciated.
Click to expand...


You probably need to switch reading sources. That info is not true. A V8 pressure plate conversion (flywheel must be modified) can be used with a stock Model-A crankshaft very satisfactorily.
 
I think where that all got started is when you use a counterweighted crank, it is good to also lighten the flywheel to offset the added rotating mass of the counterweights.

As you machine the flywheel, it is easy to go ahead and modify it to also accept a V-8 Clutch.

As Brent said, there is no reason you could not use a V-8 clutch with a stock crank.

Just my opinion,

Chris W.
 
II also had a friend a few years ago that had a 31 stripped down Roadster; he had this Roadster since he was in high school; it had a Riley 2 Port overhead, a 7 pound aluminum racing flywheel with no ring gear and it was push to start.

Ron
 
Brattons and Snyders is correct. That's where I read it. Thanks for the clarification. Besides machining the flywheel for mounting do I have to lighten as well or can you use the stock weight?
 
If you are referring to the flywheel it needs to be machined down about 30 lbs. You can use only the V-8 clutch or the Model A clutch they are not interchangeable.

Mike
 
To use a V8 clutch on a Model A flywheel, you have to machine off the top "collar" part of the flywheel that is above the flat, face of the flywheel. That will take of about 15 or so lbs. There is not really any reason to take off more unless you go to a counterbalanced crankshaft.
 
That is what I was wondering. Wasn't sure if just machining off the lip to get the mounting surface flat was all you had to do.
 
With the roads we have today you do not need all the lugging power that the original flywheel weight offered. With the ring gear a original flywheel weights about 55 pounds. The flywheel in my A weights 37 pounds , including the ring gear, after it was cut down , surfaced, drilled and tapped for the 9N pressure plate, and balanced. Balancing is very important.

The newer pressure plate is much smoother, softer to operate, and the engine RPM is much faster on the increase with the lighter flywheel.

The ideal combination of course is to have a counterbalanced crankshaft, in my opinion, there is improvement worth while with a standard crankshaft by lighting the flywheel.

Ron
 
Marc Silva,

Two years ago when I set up a friend engine I used one of Bratton,s new V8 pressure plates. It has just been fine with no problems so far.

Ron
 
Has anyone used the diaphragm pressure plate like a 1949 Chevy pickup uses? My friend's 49 pickup sure has a nice easy pedal, and that's what I'd like to try if I modified a flywheel.
 
You need to know there are 2 types of 'V-8' pressure plates.

There are the ones you want with the fly weights. So they used the lower spring rates, but as the RPM increase the force on the pressure plate increases.
The new pressure plates which I believe are from the tractor are not the fly weight type. These have the heavy pressure like the original A type.

As for the need for a counter weighted crank.

The key to the A engine is to understand Ford was very particular about precision machining on the line. With the crank and associated parts they were very very tightly matched and balanced. The center lines on the cranks were held to super tight standards. The rods were +-1 gram at each end and piston rod units would be within 4 grams on each engine.

So on the line Ford was build like a race car.

So the original engine is nothing like the rebuilt engines everyone is used to generally speaking. The engines today would be rejects on the line during the Model A production period for not being accurate enough. Rods are usually kept within 5 grams of each other total weight. Crank grinding is all over the place unless you go to a shop that knows and loves the A crank. The new pistons can have a pretty wide weight variation. I think you get the picture.

So if you make the parts of the engine like factory you will have a decent engine that likes to rev up and is easy on the bearings.

So adding counter balancing is not a necessary expense. Accurate building is.

Now clearly, if you have the money, going the extra steps of counter balancing can do something positive for the engine. Most people will not drive their cars long and hard enough to make financial sense to go the extra steps. That is a personal decision.

In any event, you need to seek out the facts to best understand what you need to do.
 
Tom Wesenberg said:
Has anyone used the diaphragm pressure plate like a 1949 Chevy pickup uses? My friend's 49 pickup sure has a nice easy pedal, and that's what I'd like to try if I modified a flywheel.
Click to expand...

I use diaphragm clutches in all of my engines.
I have a 2800 lb Hayes racing model in my 2 door.
Very easy pedal. Very similar to a stock early Ford Long type clutch.
 
Tom Wesenberg said:
Has anyone used the diaphragm pressure plate like a 1949 Chevy pickup uses? My friend's 49 pickup sure has a nice easy pedal, and that's what I'd like to try if I modified a flywheel.
Click to expand...

Tom I used a Mustang diaphragm clutch in one of my A's . I used it because I had to use a different disk with 1987 F150 transmission. The clutch disk was thinner than the A. So I used the pressure plate also. It works real well, so I think the Chev would work also. But you would need to check how thick the chev clutch disk is. A difference in thickness would cause the clutch to not release or slip.
 
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marc silva said:
Just wondering why is it that everything I have read says that you can only use the V/8 clutch with a counter weighted crank shaft? I would think that if the flywheel and clutch were balanced that it would work on the stock crankshaft.

As always, your knowledge is appreciated.
Click to expand...
You can call me about this. I have done more than a hundred and have sold them to use with stock cranks and everything else including shop made balanced and Scat cranks. I just sent one to the UK today.
 
I have put the lightened flywheel on stock cranks and stock flywheel on counterweight cranks never had a problem
James has probably done more than anyone give him a call
Colin
 
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