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Old 03-10-2018, 02:19 PM   #1
robertsjm711
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Clutch & Basic Hydraulics

I am working on the clutch on my 1953 3100 w/ 5.3 & Muncie M20. I having some issues with the clutch pedal and would like some thoughts, if possible.

I am using a Howe hydraulic throughout bearing with stock LS/Chevy pressure plate/clutch, Wilwood pedal/master combo w/ .75 bore, 1:7 ratio pedal.

My issue is the pedal motion distance. To get the clutch to completely disengage, the pedal has to be very high, ~3". The pedal hits the ~45 degree firewall before it would if it was a 90 degree, I assume this was designed for. I now own the combo after installing it so using it or some of it would be best if possible, I need to keeps cost to a minimum if possible.

My initial though was to somehow reduce the pedal travel, but this may reduce usability.

My thoughts were:
1. Change the pedal ratio - making or modifying some pedal assembly. Cons - can't mod current pedal, will change effort & other factors; pro - challenge to build and can make changes during build, flexibility?

2. Change the master cylinder bore size. Cons - can't use what I have, unknown "side effects"; pros - with bigger bore = less pedal motion/more release bearing motion/less bearing force (?? still reading up on this)

3. Create a recess in the firewall to allow for some of the needed motion. cons - might look odd; pros can use all current stuff & easy to create

Does anyone have any suggestions or thoughts?
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Old 03-10-2018, 05:51 PM   #2
mongocanfly
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Re: Clutch & Basic Hydraulics

did you check the spacing gap for the throwout bearing?.....a buddy of mine used a hyd tb and it came with a shim pack to set the proper spacing.....
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Old 03-10-2018, 06:06 PM   #3
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Re: Clutch & Basic Hydraulics

Yup, sure did. It came with that too, and I followed the directions exactly. When I pushed the clutch I don't remember noticing a delay, but will double check it today. Good thing to check.
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Old 03-10-2018, 07:06 PM   #4
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Re: Clutch & Basic Hydraulics

could you have air in the system?
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Old 03-10-2018, 07:34 PM   #5
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Re: Clutch & Basic Hydraulics

It’s possible, I bled it but that’s not a bad thing to re-do.
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Old 03-12-2018, 06:14 PM   #6
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Re: Clutch & Basic Hydraulics

From the pic you provided, the clutch pedal looks to be very high....much higher than the brake pedal....when you push in the clutch pedal does it disengage the clutch at the top or do you have to push it all the way to the floor ?
Seems you have access to see the fingers/TO bearing contact area.....get your buddy and have him push in on the clutch pedal and you can see how the TO bearing is contacting the pressure plate...
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Old 03-12-2018, 06:47 PM   #7
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Re: Clutch & Basic Hydraulics

Yeah, that's my issue, needs to come down ~3" or so. It doesn't disengage until it is just before the floor. I do remember measuring many times the 0.06" clearance between the throughout bearing & pressure plate. The shims are 0.50", and when pressing the clutch I can start to feel resistance pretty close to the top, maybe an inch or two.

The distance doesn't feel or seem that bad, its the starting point that will make it uncomfortable.

I'll be able to see the clutch in action today or tomorrow and see exactly when it engages. I was able to bleed it out and did have a couple bubbles, but it didn't help my issue.
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Old 03-12-2018, 11:05 PM   #8
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Re: Clutch & Basic Hydraulics

I would say that you need to change the pedal ratio to get the pedal down farther to start with.
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Old 03-13-2018, 11:29 AM   #9
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Re: Clutch & Basic Hydraulics

Have you considered a larger bore master cylinder? If you can move more fluid, you could then likely lower the pedal with an adjustable push rod.
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Old 03-13-2018, 11:37 AM   #10
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Re: Clutch & Basic Hydraulics

I have considered a larger cylinder, but was hoping to find someone with first (or second) hand knowledge. I think by going larger it creates less pedal motion, more release bearing motion & less bearing force.
Does this make the pedal stiffer? Or other unintended consequences? Not that it would necessarily be bad, just don't want to spend $$ on a guess.
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Old 03-13-2018, 11:30 PM   #11
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Re: Clutch & Basic Hydraulics

A larger bore clutch master will result in less pedal travel to achieve full motion of the clutch slave (hyd TOB). But that will do absolutely nothing for the very high starting position of the clutch pedal. You also have to be careful with the hydraulic TOB as to not over stroke it and cause damage. Often times an adjustable stroke limit stop is recommended on the clutch pedal to prevent such from happening.
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Old 03-13-2018, 11:49 PM   #12
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Re: Clutch & Basic Hydraulics

Yes, that pedal is adjustable and is at its upper limit. It absolutely has the ability to lower but haven’t for testing. Without it being that high it wouldn’t disengage the clutch. If I get a larger master bore and it reduced the travel, I can lower it.
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Old 04-12-2018, 06:19 PM   #13
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Re: Clutch & Basic Hydraulics

Just to give an update and close this out, I just installed a 1” bore master and it did as expected, reduced throw and incresed effort. I was able to adjust my pedal to be even with the brake and still have enough distance to disengage the clutch.
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