Overcenter spring for clutch pedal

Tech questions that don't fit above forums

Moderator: Team

Post Reply
sidestep
New Member
New Member
Posts: 42
Joined: Mon Aug 25, 2014 12:45 pm
Location: Montara Ca

Overcenter spring for clutch pedal

Post by sidestep » Thu May 05, 2016 7:17 pm

Late '50's GM application. When adjusted with the proper amount of tension, un hooked from the rest of the system, should the pedal pull to the floor and stay there after reaching the halfway point of its travel, or should it retract on its own and return to the pedal stop? My service manual does not state which is the correct operation. Currently I have it where it stays to floor, once hooked up to the rest of the linkage it will return with the help of the pressure plate spring. Any help or references to literature on the matter would be greatly appreciated.

Rizzle
Expert
Expert
Posts: 906
Joined: Mon Feb 04, 2008 10:34 pm
Location: St. Catharines, Ont

Re: Overcenter spring for clutch pedal

Post by Rizzle » Fri May 06, 2016 12:26 pm

I'm going to take WAG and say it holding the pedal down makes more sense, to assist the leg holding the clutch pedal down. Since the PP diaphragm spring returns the pedal back to a point where the pedal spring pulls the pedal back to top (I am assuming you mean by "and stay there after reaching the halfway point of its travel" that it returns to the pedal stop if less than ~1/2 stroke is achieved?), the spring should not load up the throw-out bearing at rest.

sidestep
New Member
New Member
Posts: 42
Joined: Mon Aug 25, 2014 12:45 pm
Location: Montara Ca

Re: Overcenter spring for clutch pedal

Post by sidestep » Fri May 06, 2016 12:35 pm

Rizzle, I believe you are correct. Last night skimming thru a different service manual they stated the use of Borg and beck 3 finger style pressure plates required a fair amount of pedal effort and the over center spring assisted in holding the pedal down, disengaged, say at a stop sign. Thanks for taking the time.

BigBlocksOnTop2
Pro
Pro
Posts: 388
Joined: Thu Mar 21, 2013 12:03 pm
Location: Chancellorsville Battle Field, Chancellorsville, Virginia

Re: Overcenter spring for clutch pedal

Post by BigBlocksOnTop2 » Fri May 06, 2016 2:45 pm

Its correct and is working as designed. One thing to remember is, if using a diaphragm clutch, remove that over the center spring. Not doing so, when making a high rpm gear change, the pedal will stay on the floor until the motor rpm decreases.

sidestep
New Member
New Member
Posts: 42
Joined: Mon Aug 25, 2014 12:45 pm
Location: Montara Ca

Re: Overcenter spring for clutch pedal

Post by sidestep » Fri May 06, 2016 4:00 pm

BBOT-- it is a diaphragm pressure plate McLeod super street pro. I have a second return spring that is attached to the z bar on one side and too a block mounted bracket on the other. Do you think this will aid in full release at higher rpms?

Rizzle
Expert
Expert
Posts: 906
Joined: Mon Feb 04, 2008 10:34 pm
Location: St. Catharines, Ont

Re: Overcenter spring for clutch pedal

Post by Rizzle » Fri May 06, 2016 6:18 pm

BigBlocksOnTop2 wrote:Its correct and is working as designed. One thing to remember is, if using a diaphragm clutch, remove that over the center spring. Not doing so, when making a high rpm gear change, the pedal will stay on the floor until the motor rpm decreases.
I had never heard of this (I did not grow up in the era of mechanical clutches) so it looked it up. (thank you for mentioning it BTW, I learned something 'new' today)
It seems to be a common question on whether to remove the over-center spring for diaphram clutches, and it seems that if you have an adjustable, positive pedal stop to prevent over stroking the diaphragm spring (which causes the spring to work backwards), the over-center spring can be left in place. Without another spring, removing this spring can result in the throwout bearing constantly being engaged.

However, since OP said he had a second return spring on the z-bar (I am again guessing this is not set up to work as the over-center spring) he can only benefit from removing the over-center spring as you suggested.

sidestep
New Member
New Member
Posts: 42
Joined: Mon Aug 25, 2014 12:45 pm
Location: Montara Ca

Re: Overcenter spring for clutch pedal

Post by sidestep » Fri May 06, 2016 8:40 pm

I had a center force dual friction pressure plate in the car a while ago. Went to pull 2nd at 7000 and the clutch pedal stuck to the floor. Ever since then I added a second spring. If I'm better off without the over center spring I'll remove it. Thanks guys, very helpful and informative. Ray S

bill jones
Guru
Guru
Posts: 2485
Joined: Sun Sep 05, 2004 6:38 pm
Location: salt lake city, ut
Contact:

Re: Overcenter spring for clutch pedal

Post by bill jones » Sun May 08, 2016 10:41 pm

-if you are using the cross bar tube from the frame to the side of the engine---that has the two linkage arms welded to that bar---it's a good idea to reinforce those weld joints so they don't crack or break away during spirited shifting.

BigBlocksOnTop2
Pro
Pro
Posts: 388
Joined: Thu Mar 21, 2013 12:03 pm
Location: Chancellorsville Battle Field, Chancellorsville, Virginia

Re: Overcenter spring for clutch pedal

Post by BigBlocksOnTop2 » Tue May 10, 2016 5:15 pm

sidestep wrote:BBOT-- it is a diaphragm pressure plate McLeod super street pro. I have a second return spring that is attached to the z bar on one side and too a block mounted bracket on the other. Do you think this will aid in full release at higher rpms?
I just got back to ST. If it is the spring I think that it is, it is there only to keep the release bearing off the clutch fingers and also to keep the adjustment rod from falling off the clutch fork.

sidestep
New Member
New Member
Posts: 42
Joined: Mon Aug 25, 2014 12:45 pm
Location: Montara Ca

Re: Overcenter spring for clutch pedal

Post by sidestep » Wed May 11, 2016 7:19 pm

Yes I have a very small spring that is attatched to the fork on one end and the lower rod on the other to pull the slack out of the system and keep the throwout bearing of the pressure plate. I have added a clutch return spring from a 1966 mustang I drilled a hole on the lower arm of the z bar and cut a bracket that is mounted to the side of the block where the motor mounts would go (sbc). I'll pull the over center spring and leave the other one in place and take it for a ride.

Post Reply