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Hot Rods Who's running external clutch slaves

Discussion in 'The Hokey Ass Message Board' started by model A hooligan, Apr 28, 2018.

  1. no55mad
    Joined: Dec 15, 2006
    Posts: 1,765

    from nipomo, ca

    Yes the pedal pressure is definitely greater but not unbearable. Not as bad as the old competition clutches from the 60's. Because a longer fork was used, there was a mechanical advantage there to lessen pedal pressure. Maybe a 7/8" master would have worked but then maybe Wilwood didn't offer that. If you contact Wilwood, there tech help is very good.
  2. nrgwizard
    Joined: Aug 18, 2006
    Posts: 983

    from Minn. uSA

    If you can easily move the clutch pedal, by hand, thru 1/2 of the travel before you feel resistance, either you have too much freeplay twixt the TO bearing/clutch fingers/clutch fork (which you said you adjusted out); or you have a hyd leak/fluid-bypass somewhere *inside* the system. & I'd guess it's in the 1st half of the master cyl bore (the fluid is dumping back into the res before some check-valve is closing/being bypassed). To check, get a 2 good steel rules & position them so's you can watch & accurately measure the travel of both the pedal & the slave, esp at the point of resistance. I'm guessing that you're getting very little movement of the slave for the 1st half of pedal travel. Just because parts are new, doesn't mean they are made correctly. But at least it does make for more diagnostic fun. ;( .
    Als,o still could be some air in the system, so a rebleed might be warranted. I also had a ford ranger that had issues w/the slave. Took it to the dealer - they got to do it 3 times + about that many extra rebleeds 'till it got right. The 1st 2 replacement slaves were bad out of stock n OEM parts, too. The 3rd was ok, but due to Fords' incredible engineering efforts, they designed the clutch master to be upsidedown w/the bleeder at the bottom. Just to make sure bleeding was more fun... <shrug> . The tech was suitably impressed... :D . Similar thing happened when I r&r'd the brake master cyl, brand new one was leaking internally, got a different one, = ok, = good brakes.
    edit: Guess you type/post faster than I do.
  3. I got my MC lightly used from a guy. He said it worked fine and took it off when it was pretty much new due to him mistakenly thought it was bad but had a problem somewhere else.

    They do offer a 7/8 and a 1" master. Fulton also offers a full sized one that if I could shoe horn it in there may be better since it's output brake line is lower and would not create a high spot in the lines such as I have now.

  4. I had a ranger with hydraulic throwout bearing. Not the same as what I'm doing. But yes well aware of the downward pointing MC design flaw they had. What a pain! I carried a bleeder wrench in it and was going to cut a hole in the floor to do one man bleeds when I was out and about because I could only get about a week out of it before it needed bleeding.

    Also I feel a small bit or resistance the whole way with the pedal but it's so minor my arm can push it without problem at all. It gets a little firmer at the very end of the stroke. I agree, I don't think the slave is moving much in the first half. I'll have to remove my floor so I can see while inside the car
  5. Ok ive got a mid 80,s 3/4 ton chevy. and when I got it it had been setting and the clutch wouldn't release. I filled the resevior to the top and pumped and never got any release. no bleed screw on the slave cyl. I even pulled the trans thinking the clutch disk was stuck to the flywheel. Nope all of it including the flywheel was brand new. Finally searched Utube. Learned you have to remove the downward slanting master cyl from the firewall and tilt it and use the bleed screw on the master and bled it by hand. It now works sorta not always a clean release and is slow to engage between shifts
  6. Is this the stuff?
    Not sure why I need to hunt it down ????

    So the master 3/4" bore can take 1.40" stroke
    Amd the slave 7/8" bore can deliver a MAX of 1-1/8" travel.
    #1 - does 1-1/8 at slave location move the Throwout bearing enough?
    Remember the required movement of the T O bearing is where you need to begin.

    #2 that master @3/4 is going to most of every bit of its available 1.4 stroke to move the slave @7/8 to its full 1.25




    Attached Files:

  7. metlmunchr
    Joined: Jan 16, 2010
    Posts: 708


    Without going thru the math here, since some people don't seem to give a shit about math anyway, the 3/4 bore m/c with 1.4" active travel would be a perfect match with the 7/8 pull cylinder if the pull cylinder has a 1/4" internal rod. Full stroke of the m/c would give 1.12" travel at the slave.

    6:1 pedal ratio would require 8.4" pedal travel for full stroke of m/c. 5" of travel at the pedal is only going to give about 11/16 stroke at the slave, and that's not accounting for the dead travel as the piston moves forward to cover the port between the cylinder and the reservoir. Say for example the piston moves 3/16" to cover the port. That means the first 1 1/8" of pedal travel is used up before any fluid begins to move. The active pedal travel is then reduced from 5" to about 4", and the stroke at the slave would be reduced to about 1/2".

    7/8 bore m/c at the same 5" pedal travel would give about 0.9" stroke at the slave with a 35% increase in pedal effort, or about 0.7" of slave travel if it takes 3/16" piston travel to cover the port.

    Does a pull type slave have an internal spring to return it to the fully extended position? If not, then the release arm would need to be spring loaded to allow the t/o brg to sit as close as possible to the clutch fingers and still assure that it doesn't ride on the fingers. I don't see a spring to keep tension on the release arm.

    Another possible problem is the "bits of hose" at two locations. If these are short brake hoses then they're probably not a problem. But if they're any other kind of hose then they could could be acting like a pair of balloons in the line and reducing the amount of travel at the slave.

    Hydraulic clutches can be hard to bleed, and especially so if there's any inverted trap in the line. I dealt with the damn things for years on mobile cranes where the line from under the dash back to the slave could be 8 to 10 feet long. Only sure fire way I ever found was to take a big hypodermic type syringe and force fluid backward up thru the line from the bleed port at the slave to the m/c.
    46international and F&J like this.
  8. If you are by yourself, you can always put your phone camera on video and lay it under the car, go thru the motions and review the video to see what the slave is doing.

    Sent from my Nexus 5X using The H.A.M.B. mobile app

  9. Yeah, I did post what they was more than one time. You are right about the master needing every bit of stroke to work that slave. That's why I'm considering going up in MC size

  10. They are less than 12 inches of rubber and they are DOT brake line,that I hade professionally made. The slave does have a internal spring though it is not very strong at all. You are correct with your math with the amount of pedal movement and 1/2 movement at the SC. That does seem to be spot on with what I have going on.

    Also I most certainly do not have room for 8 inches of pedal movement
    Last edited: May 12, 2018
  11. Never saw that the stroke for either cylinder was ever mentioned, but I asked for it several times and then a couple more. Didn't see anything about the pedal travel distance or the masters actual stroke till the post about your boss's input. And certainly more than once I've asked what the distance is that the T O bearing needs to move and that is where this project needs to start from. And that its math, and that some things need to be known.

    Im sure you see the input metal muncher had, that's all the math based on the strokes and info that JUST showed up. As great as his post is and helpful as it is, without the missing info of the distance the TO bearing needs to move, and the lengths of the clutch fork modifications, or without the full size draw up of it that I told you how to do, there's not much any one on the other side of the screen can do to help.
  12. I suppose there isn't such a thing as too big a master cyl? The old ford trucks with the Hyd clutch release. they had two firewall mounted master cyls. And they where identical. One for the brakes and the other to activate just one slave cyl.
  13. Im not here to argue.
    Last edited: May 13, 2018
  14. Yeah I have a thread on here about that master. Very aware of it but didn't want it hanging on my firewall. I'm channeled and the valve cover would be close

    I don't know, I think if it's too big the pedal gets too hard. The Chevy master used 1 1/8 clutch slave. Im not sure what a bigger master than the slave yealds other than more slave movement.

    I did look at a lot of reviews for 1" master cylinders and a ton of folks said they bought it due to their 3/4 nit moving enough. I'm pretty sure it comes down to pedal movement. Some of my very first posts was it feels like if the pedal was in my lap and I pushed it to the headlight it would work. I've read a 1" master would work with 5 1/2 pedal travel which is about what I got it seems. So to me the only thing I can do is try it. Just not sure which, wilwoods has a bit longer stroke than the Tilton
    Last edited: May 13, 2018
  15. My post wasn't meant to be argumentative, but if you do find portions of argumentative try to ignore those and find the other parts of the post and fill in the missing pieces to the puzzle. I don't recall even seeing what style pressure plate or it's specs.

  16. That's fair, I can dig that.

    I don't really have the numbers. I can tell you it's a curved finger clutch and short bearing. It's a Luk clutch,that says fit 66 Malibu but I describe them as 'corvette' style with the raised curved fingers.its a 69 camaro muncie, and just a aftermarket 153t flywheel with a 'pioneer' fork that I shortened. I do not have the part number for the clutch. Thrown that box out a while ago.
  17. It's this. But I changed to a metal throw out bearing. It's the same size (length) bearing though

    Attached Files:

  18. This is the exact pedal. The other items you posted was correct

    Attached Files:

  19. ....Edited

    You'd want to move that hole up away from the pivot.
    Last edited: May 14, 2018
  20. Here's an article, within it is some valuable information on clutch release bearing travel distance. Maximize the movement by adjusting the cluch fork angles all kinds of cool stuff. Issues with solutions, and how to measure some critical stuff.

    I hope you find time to read it.
  21. mcsfabrication
    Joined: Nov 26, 2006
    Posts: 713


    Closer to the pivot would decrease length of stroke.
    What is the distance you can push the piston in the master without a line connected (piston bottoms out in the cylinder?)
    How much distance will the hole in the pedal push the rod before the pedal hits the firewall?
  22. 31- in going to check that out.

    Would making the pivot bother the master how the rod would be at an angle? I'm guessing no since you mentioned it may help
  23. Not sure,never looked. I'll have to disconnect the lines and pull it out. I planned on doing that this week.
  24. OK!, just back from Vegas trying to empty the in-laws house. So here goes where I left off last on Friday morn. I'm not saying math can't work. My reply about math being a man made thing was to model A hooligan. model A hooligan clearly said "how do I know" to you in regards to your asking him why he hasn't done the math.
  25. model A hoolagan, I last left you with how to check and get more travel from your puller set up. I see many have been helping on this as well. :) I left hoping some one would ask to see if your clutch disengages before doing more work and buying more parts if not needed. So I'll ask then. Have you checked to see if the clutch works as is. The fork doesn't need a full 1 3/8" travel. Not unless you want your pressure plate to go way over center. Remember, your fork is short now. Right?
  26. Oh hell, my bad on the brain fart.
    Yes, you'd want to move the hole away from the pivot to get the master to stroke more.

    The specs on that pedal say it's 12-1/4" long with 6:1 ratio. That means the tab hole to pivot should be about 2". If you can move the hole UP with a tab that would increase your stroke.

    The angle of the rod may matter or it may not. Depends on the cup and rod of the master.
    Last edited: May 14, 2018
  27. I just thought of this, could your TO bearing be too short? if you have the room for access, try to cut a U out of plywood and slip it between the bearing and clutch plate. See how that works. IIRC GM had 3 lengths of TO bearings.
  28. My fork has less than an inch of travel to it.
  29. Ive already mentioned I had the right bearing and it was adjusted to have all the slack taken out
  30. Going to order a larger master to try since I don't have more room for more stroke.

    Would a longer stroke or shorter stroke master be a better option. I figured the longer one (wilwood) can't be fully utilized anyway. Was thinking of the shorter tilton

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