Hard clutch pedal

[genolan]

I have a Rousch 427r with a TKO600 and the clutch pedal has always been pretty stiff. I have knee issues and wanted to get a lighter clutch any recommendation. I bought the car used and have no record of what the current setup is.

[spdbrake]

Switching to a twin disk clutch will help your leg considerably. Stay with a street twin disk category which will hold twice the torque of your current clutch most likely and be a lot lighter to operate. You will have to go to an internal slave/throwout bearing. Most require a stop bolt on the clutch pedal (where internal slaves get most of their complaints. Folks skip that step & the slave hyperextends and starts leaking)

While you're in there change the aft crank seal: Fel-Pro BS 40645
and the forward input seal on the TKO: Timken 3638 Seal
Pilot bearing: M-7600-A

[genolan]

Thanks, does the trans drop out easy or do you need to pull the motor and trans together?

[Tommy]

A more modest reduction in pedal pressure may be possible with different pedal geometry or a smaller diameter master cylinder for the clutch. Both of these approaches can reduce the force required to move the pedal but will require the pedal to be move farther than before. Someone familiar with your brand would have to provide detailed guidance on the feasibility of either approach.

[Cashburn]

Yes to the twin disc. We install on 80% of our builds. Can keep the external slave too.

[spdbrake]

Yes it can be done. There are several steps to be taken in preparation .
Radiator hoses, motor mounts, sidepipes, fuel lines, supporting the engine due to Aft CG.
Still much less than pulling the motor for sure.


This adapter works well if you are using jack stands or placing your floor jack on top of a toolbox or table if using a two post lift
https://www.summitracing.com/parts/WMR-W41044

[spdbrake]

Originally Posted by Cashburn

Yes to the twin disc. We install on 80% of our builds. Can keep the external slave too.

Jay,
What twin clutches are you using. I wasn't aware of any that weren't too thick even with an adjustable fork pivot ball.

Thanks for any info you can provide.

[genolan]

Originally Posted by Cashburn

Yes to the twin disc. We install on 80% of our builds. Can keep the external slave too.

Jay can you give me a make and model number for the clutch you recommended to reduce the amount of pressure on my leg

[Cashburn]

https://www.summitracing.com/parts/mcl-6913-07c

[Cashburn]

Originally Posted by spdbrake

Jay,
What twin clutches are you using. I wasn't aware of any that weren't too thick even with an adjustable fork pivot ball.

Thanks for any info you can provide.

We've used McLeod and Centerforce.

[spdbrake]

Excellent!! Thank you

I'm thinking of using the 6913-07 as it's the same unit minus the adjustable fork ball stud and throwout bearing. I have both already.
https://www.summitracing.com/parts/m...3-07/make/ford

[genolan]

Besides replacing the clutch any other methods to reduce pedal pressure? I just put in a new wilwood master and slave .75 bore

[spdbrake]

You can go to a 7/8" slave and the pedal will be easier. But the throw may not be enough to disengage the clutch.
Random made up numbers here: All things being equal you are at a 1:1 ratio. 3/4 master and 3/4 slave. So say your current master moves 50cc in 1.0" of travel in the piston, then your slave will take in 50cc and also move 1.0" of travel.
Switching to the 7/8" slave it will move approx .75" if 50cc is supplied.
If disengagement is an issue in this configuration, you can still disconnect your master pressure hose. Adjust the clevis rod on the master so it shanks out internally at approx the same time the pedal arm touches the carpet. This is to ensure you are getting benefit of the full capabilities of the 3/4" master. You may also end up with a tall clutch pedal. (does not sit even with the brake pedal)

[genolan]

Is there a clutch assist spring on the pedal?

[HTM101]

A larger master cylinder bore will increase pedal pressure. Pedal pressure to move my RAM single disc clutch has always been leg strengthening. Two months ago I replaced my .75" Girling clutch master cylinder, with a .625" Girling. The pedal effort is now substantially easier.

A Google search on the subject of master cylinder sizes will substantiate my statement. Here is one of them.

https://techtalk.mpbrakes.com/master...nce-and-effort

[HTM101]

A larger master cylinder bore will increase pedal pressure. Pedal pressure to move my RAM pressure plate and single disc clutch has always been leg strengthening. Two months ago I replaced my .75" Girling clutch master cylinder, with a .625" Girling. The pedal effort is now substantially easier.

A Google search on the subject of master cylinder sizes will substantiate my statement. Here is one of them.

https://techtalk.mpbrakes.com/master...nce-and-effort

[genolan]

Originally Posted by HTM101

A larger master cylinder bore will increase pedal pressure. Pedal pressure to move my RAM pressure plate and single disc clutch has always been leg strengthening. Two months ago I replaced my .75" Girling clutch master cylinder, with a .625" Girling. The pedal effort is now substantially easier.

A Google search on the subject of master cylinder sizes will substantiate my statement. Here is one of them.

https://techtalk.mpbrakes.com/master...nce-and-effort

Since the slave is easy to replace does the same rationale apply to the slave bore size except in the opposite direction larger makes pedal easier.

[genolan]

Summing it up a 1/8 reduction in master cylinder or a 1/8 increase in slave cylinder will reduce pedal pressure by approximately 16% . Question are either solution the same or is one better than the other. The slave is way easier to change than master.

[genolan]

Does anyone know the part number for a slave clutch that has a 7/8 inch bore and bolts right on ?

[spdbrake]

Originally Posted by genolan

Besides replacing the clutch any other methods to reduce pedal pressure? I just put in a new wilwood master and slave .75 bore

Gary, The Wilwood slave (pull type) is a 7/8" unit.
https://www.wilwood.com/MasterCylind...temno=260-1333
Can you you clarify what you installed?