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  1. #21
    Join Date
    Feb 2011
    Location
    Devon
    Posts
    267
    Hi Mark, fairly sure I have a new Girling 0.75 master cylinder somewhere, if you decide you need one let me know.

    Geoff

  2. #22
    Join Date
    Jan 2002
    Location
    Marlow
    Age
    67
    Posts
    1,724
    Hi Mark, I had a Scorpio bellows operating a Twin Plate Mcloud clutch, I changed this to a single plate that Mcloud's said would have the same throw and it took two goes to get the correct shim and engine out three times.

    Cheers Clive
    On On

  3. #23
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    320
    My golden rule when trying to solve a problem is if you are adding complexity you are going further away from a solution not closer to.

    What is a smaller diameter master going to do? It will give you a higher line pressure (relative to foot pressure) and reduced fluid displacement.
    Will the change in mount position increase or decrease you leverage? If it increases it you will end up with even higher line pressure but correspondingly less fluid displacement. If it goes the otherway you may end up back were you started.

    If your pedal is currently going solid you ate pushing against something equally solid, all you are going to do is push harder on this.

    When I did mine I located the bearing on the mount on the front of the gearbox and hooked up and bled a master cylinder. This was with the gearbox on the floor and the master cylinder on the end of a flexible pipe. I checked the distance from the bellhousing to engine mount face o the bearing face with bearing retracted, made sure it was the same as the clutch fingers to the same face (plus a clearance). Then I pumped the master cylinder and made sure the bearing extended. More importantly I then pushed the piston back to make sure it returned. Only when all this passed (which it did first time) did I move on and mount the gearbox to the engine. Still out of the car at this point.

    Then with the 'box in gear I applied pressure to the master cylinder (bolted a mastic gun to the back of it!) and pumped until I the clutch disengaged (I could turn the gearbox output shaft) then released the pressure and made sure the clutch re engaged, only then did I proceed.

    So what is wrong with your setup?
    1) your pedal is not actually solid but hard. Ok more presure will help, but that must be one kick ass clutch, I was able to move mine by hand!
    2) you are pumping the pedal until it contacts something solid (either clutch or bearing end stop), if it's the clutch then it seems the fingers are not pushing the bearing back so either your clutch is broke or your hydraulic circuit is not letting fluid return.
    3) something I've not thought of. Yet!

    Some questions.
    1) What is the dimension from the engine rear face (bellhousing mount) to clutch fingers?
    2) What is the dimension from the bell housing front face to the bearing face retracted?
    3) What is the same dimension with the bearing extended?

    Should you give up and change to a mechanical, non-concentric slave as some have suggested? Why would you do that? I think every production car in existence today uses a concentric slave so there is definitely nothing wrong with the concept.
    There is much going for it. It has less moving parts and force direciton changes so is mere efficient (more of your leg power will be transmitted to the bearing) with less lost motion meaning for a given pedal force you will get a shorter pedal throw which was important to me in the cobra with its confined footwell
    The reason home buidlers have isues is because they get ithe wrong not becaus the conce is flawed. I woder what thsee problems are.

    And I still think some pictures or diagrams of your measurements would really help here.
    Last edited by GDCobra; 06-10-18 at 03:02 PM.

  4. #24
    Join Date
    Dec 2009
    Location
    Barton Mills,Bury st Edmunds,Suffolk
    Age
    48
    Posts
    216
    Thanks GD, I will send the measurements later and I can confirm that McLeod said measurements were spot on.
    mark chambers
    Dax de Dion 350 Chevy

  5. #25
    Join Date
    Dec 2009
    Location
    Barton Mills,Bury st Edmunds,Suffolk
    Age
    48
    Posts
    216
    Thanks Geoff not sure where this is going at the moment thanks for the offer, Mark.
    mark chambers
    Dax de Dion 350 Chevy

  6. #26
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
    Age
    54
    Posts
    9,351
    I have to say I agree with GDCobra, if the clutch is solid and you cant move the pedal at all what differance is changing the master cylinder going to make ?

  7. #27
    Join Date
    Dec 2009
    Location
    Barton Mills,Bury st Edmunds,Suffolk
    Age
    48
    Posts
    216
    Ok, so McLeod ask for certain measurements to determine which CRB will suit your application I have a Borg Warner WC series 5 speed manual that was from a 1992 V8 Camaro all rebuilt and ready to go with a bellhousing to bolt behind a SBC. So if your clearance from clutch fingers when all fitted and torqued to outside of bellhousing is more or less than 3" decifers which CRB you need? This in ours is 63.55mm/2.502" and is the A measurement, then gearbox face to release bearing face retracted is measurement B and is 59mm / 2.323 so you then subtract B from A giving you 4.55mm / 0.179. To get this bolt on bearing to function correctly you need a minimum of 0.100" to a maximum of 0.250". So McLeod have confirmed that this is spot on, so why is it not working?
    So pedal ratio? The best is 6:1 but I've done the approximate measurements and I have 5 1/2" pedal travel the centre of pedal to pivot is 10" and the cylinder is approx 3" above the pivot point with a 0.875. 7/8" cylinder with about 1" of travel,its following this that the man from McLeod says change to a 3/4" cylinder and I have no mechanical leverage?
    Anyway box is out again and we are going to rig it up to see if bearing is releasing/ retracting but when I removed the clutch i was amazed at how the fingers on the clutch cover released and I'm thinking that this may be the problem? Going to talk to real steel and Dax on Monday !
    mark chambers
    Dax de Dion 350 Chevy

  8. #28
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    320
    Quote Originally Posted by mark chambers View Post
    Ok, so McLeod ask for certain measurements to determine which CRB will suit your application I have a Borg Warner WC series 5 speed manual that was from a 1992 V8 Camaro all rebuilt and ready to go with a bellhousing to bolt behind a SBC. So if your clearance from clutch fingers when all fitted and torqued to outside of bellhousing is more or less than 3" decifers which CRB you need? This in ours is 63.55mm/2.502" and is the A measurement, then gearbox face to release bearing face retracted is measurement B and is 59mm / 2.323 so you then subtract B from A giving you 4.55mm / 0.179. To get this bolt on bearing to function correctly you need a minimum of 0.100" to a maximum of 0.250". So McLeod have confirmed that this is spot on, so why is it not working?
    So pedal ratio? The best is 6:1 but I've done the approximate measurements and I have 5 1/2" pedal travel the centre of pedal to pivot is 10" and the cylinder is approx 3" above the pivot point with a 0.875. 7/8" cylinder with about 1" of travel,its following this that the man from McLeod says change to a 3/4" cylinder and I have no mechanical leverage?
    Anyway box is out again and we are going to rig it up to see if bearing is releasing/ retracting but when I removed the clutch i was amazed at how the fingers on the clutch cover released and I'm thinking that this may be the problem? Going to talk to real steel and Dax on Monday !

    I'm guessing from the above that you didn't get my point about removing complexity!
    Distance A, distance B? It means absolutely nothing to me. The only thing you need to worry about with the bearing is if you have enough space to fit it and then (and only then) if the bearing has enough stroke to operate the clutch.

    Please, please please, give us a diagram of your dimensions, it will make a whole lot more sense than quoting the blurb from McCleod. What is the distance between the clutch fingers and the bearing face (retracted) when all is bolted together (before any movement of the clutch pedal?

  9. #29
    Join Date
    Dec 2009
    Location
    Barton Mills,Bury st Edmunds,Suffolk
    Age
    48
    Posts
    216

    Hydraulic release bearing dimensions

    Hi Gd Cobra i hopefully have attached a diagrammatic overview of the set up should make sense i will try and forward one of the master cylinder but that is a fairly standard position and fit above the pedal box on the drivers side upper foot-well. Look forward to your response.
    Attached Images Attached Images
    mark chambers
    Dax de Dion 350 Chevy

  10. #30
    Join Date
    Dec 2009
    Location
    Barton Mills,Bury st Edmunds,Suffolk
    Age
    48
    Posts
    216

    Other images

    GD Cobra here are the other pictures just for reference of the bearing on gearbox,cylinder location and pedal box, thanks Mark.
    Attached Images Attached Images
    mark chambers
    Dax de Dion 350 Chevy

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