Over Center Spring question

[Jay Williamson]

I’ve seen a lot of discussion regarding the over center spring. I have a 67 R/T 4 speed that has had the over center spring removed and I hate it. Obviously someone put an aftermarket diaphragm clutch in and it makes my clutch pedal sit about 2-3” lower than the brake pedal. My question is…Is there any harm in leaving the over center spring in there? It’s not going to come up any higher than the stop will allow, right? Thanks for your advice or opinion

 

[hunt2elk]

If you leave the big spring in place with a diaphram style clutch, the issue is that the pedal could stay at the floor when driving it hard, not a good deal. Sounds like you just need to adjust your clutch rod?

 

[Jay Williamson]

So the spring makes the pedal come up right? Why would it cause it to stay on the floor? I would think the spring would have the opposite effect

 

[steve340]

The spring is sometimes called the clutch assist spring - this helps to depress the clutch and is the reason some pedals will stay on the floor.
It really relies on the old Borg and Beck style pressure plate "pushing back" on the clutch mechanism to get it off the toe board.
I have had cars with diaphragm clutches with and without the assist spring and they worked fine.
You could fit the spring and see if your car is OK.
In my experience there is no guarantee the clutch/brake will line up if you fit the spring.

 

[dadsbee]

It's called an "over center" spring for a reason. It returns the pedal once it's over center. Below center it helps with the pedal force and a b&b clutch plate will push the pedal back past center and then the spring takes over. Unhook your linkage and push the clutch pedal down... don't have your hand under it at the floor! Then you'll know why it can stay down with a diaphragm plate.

 

[4mulas]

I think you just need to adjust your clutch properly, and make sure you have the proper linkage/rod. Pedal Shouldn’t be so low.

dadsbee post clearly explains the over-centre spring

 

[moparedtn]

My experiences with the diaphragm clutches (most recently, a CenterForce DualFriction) have been that
in order for the clutch to be adjusted properly with them in my car ('68 GTX), the pedal winds up being
about where the OP describes.
I've also tried leaving the o-c spring in place on a diaphragm and sure enough, that sucker stayed down
first time I romped on the car; it took stopping the car to get a toe under the pedal to return it and I did
NOT like the feeling it gave as the clutch returned to the "right side" of things.

We had a whole big discussion about this in one of my threads on here....results being if I ultimately wanted
the pedal to come the rest of the way back up without using the over-center spring, then I was going to
have to customize a lighter spring up under the dash somewhere to pull it the rest of the way up.

I currently have a B&B type in the car (a Ram unit, which I don't care for) as a result. I would LOVE to find
just a good old fashioned stock type 11" B&B clutch for the ol' 18 spline.

 

[Jay Williamson]

It's called an "over center" spring for a reason. It returns the pedal once it's over center. Below center it helps with the pedal force and a b&b clutch plate will push the pedal back past center and then the spring takes over. Unhook your linkage and push the clutch pedal down... don't have your hand under it at the floor! Then you'll know why it can stay down with a diaphragm plate.

This makes sense now. Thanks for the explanation. Sounds like the diaphragm clutch will not push the pedal past center

 

[hunt2elk]

I have diaphram clutches on all 3 of my cars and the over center springs are removed. All my pedals come up to where they should be. Did you try adjusting yours?

 

[Mick56]

Without any type of spring to pull the pedal back up, you need to make sure the throwout bearing is not resting on the clutch fingers, and spinning all the time.

 

[steve340]

Do you have the spring on the release fork?
I have seen a lot of cars that this has been left off.

 

[gkent]

I think you just need to adjust your clutch properly,

Yup !!

 

[Jay Williamson]

I was able to adjust the linkage. Only aboutcanothe4 1/4” adjustment left on the rod

 

[Jay Williamson]

Do you have the spring on the release fork?
I have seen a lot of cars that this has been left off.

Yes

 

[Daves69]

I was able to adjust the linkage. Only aboutcanothe4 1/4” adjustment left on the rod

Did it bring the pedal up to where you want it? An Abody rod may provide more thread if the angle is acceptable.
BTW, The longer you make that rod with adjustment, the deeper the release bearing pushes the cover fingers toward the disc hub. A pedal stop may be something to consider.
I've heard of brake shoe return springs custom bent to replace the heavy OC.