Page 1 of 2 12 LastLast
Results 1 to 20 of 30

Thread: Master cylinder packing pieces (shims)

Forum to discuss Austin Healey Sports Cars

  1. #1
    Jedi Knight Lin's Avatar
    Join Date
    Apr 2002
    Location
    Bradenton, FL
    Posts
    946
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    4
    Thanked in
    3 Posts

    Master cylinder packing pieces (shims)

    Hi folks,
    I am getting ready to replace the clutch and brake masters cylinders on my 60 BT7 as preventative maintenance. I have done this a number of times since the 1970s. The Moss catalog (and others) shows a packing piece or shim that is actually two pieces that fits between the master and the pedal box. I never recall seeing shims on the clutch pedal master, but I have always replaced the original shims on the brake master. Are there supposed to be shims on the clutch master also? What do these packing pieces (shims) do, other than move the master cylinder and therefore the pedal ever so slightly toward the front of the car?

    Your thoughts are appreciated.

    Lin
    1959 AN5 Bugeye - now with my son 😀
    1960 BT7 3000 MKI
    1987 Alfa Romeo Spider Quadrifoglio

  2. #2
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    507
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    13
    Thanked in
    13 Posts

    Re: Master cylinder packing pieces (shims)

    I don't know for sure but I have always thought they were only for adjusting pedal height. My '57 100-6 has shims under the brake master but my '60 3000 has them under the clutch master in order to have even pedal height. The shims I have are all about 1/16" and that translates to 3/16" or more in pedal height change, so some cars need shims on one or the other to get the pedals even.

    I could never figure out any other reason for them, but if there is another reason I would love to know.

    Dave

  3. #3
    Jedi Knight Lin's Avatar
    Join Date
    Apr 2002
    Location
    Bradenton, FL
    Posts
    946
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    4
    Thanked in
    3 Posts

    Re: Master cylinder packing pieces (shims)

    So... adding the shim drops the pedal, right?
    Lin
    1959 AN5 Bugeye - now with my son 😀
    1960 BT7 3000 MKI
    1987 Alfa Romeo Spider Quadrifoglio

  4. #4
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    507
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    13
    Thanked in
    13 Posts

    Re: Master cylinder packing pieces (shims)

    Correct. If your pedals are even now, probably just replace them where they are but if one is off this is the time to adjust.

    I don't know if adjusting with the packing pieces is needed because of variables in manufacturing the car or variables in manufacturing the cylinders? So, if you are replacing the cylinders there may be a need to adjust?
    I buy new cylinders from Pegasus and they come with a threaded adjustable push rod that won't work on a Healey and the Healey push rod is not adjustable, so the shims are the only way I know to adjust pedals.

    dave

  5. #5
    Yoda HealeyRick's Avatar
    Join Date
    Apr 2004
    Location
    Massachusetts
    Posts
    5,792
    Thanks Thanks Given 
    16
    Thanks Thanks Received 
    36
    Thanked in
    32 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by red57 View Post
    I buy new cylinders from Pegasus and they come with a threaded adjustable push rod that won't work on a Healey and the Healey push rod is not adjustable, so the shims are the only way I know to adjust pedals.

    dave
    My source is Pegasus, too. They still stock Girling cylinders.
    Rick

  6. #6
    Luke Skywalker vette's Avatar
    Join Date
    May 2002
    Location
    Pa.
    Posts
    1,711
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    13
    Thanked in
    11 Posts

    Re: Master cylinder packing pieces (shims)

    I have shims on both my brake & clutch master cylinders and my pedals are even. They were that way when I bought the car 20 years ago. It is a BJ7. Moss' cataloge shows the shims on both the clutch and the brake and it is the same part number.
    About TV Shows-
    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

  7. #7
    Yoda steveg's Avatar
    Join Date
    Sep 2007
    Location
    Altadena, CA
    Posts
    3,755
    Thanks Thanks Given 
    90
    Thanks Thanks Received 
    142
    Thanked in
    121 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by red57 View Post
    ...I buy new cylinders from Pegasus and they come with a threaded adjustable push rod that won't work on a Healey...
    dave
    Dave - please explain why. Thank you.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow


  8. #8
    Luke Skywalker vette's Avatar
    Join Date
    May 2002
    Location
    Pa.
    Posts
    1,711
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    13
    Thanked in
    11 Posts

    Re: Master cylinder packing pieces (shims)

    My opinion has been that because of the none adjustability of the geometery of the pedal and rod that these shims were needed to keep the pistons from traveling into the bores too far. Just an uniformed opinion.
    About TV Shows-
    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

  9. #9
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    507
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    13
    Thanked in
    13 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by steveg View Post
    Dave - please explain why. Thank you.

    Not sure what part of my post you are questioning;


    I buy from Pegasus because they have the best choices of bores in stock and are cheapest (at least they used to be).

    On the push rod, I guess I should have qualified - if you want to use the threaded push rods that come with the Girlings from Pegasus you would have to add clevis ends & make sure the length is right. IMO, easier and better to just use the non-adjustable Healey ones.
    IMG_2417.jpg

    Top is Healey, bottom is as received from Pegasus

    Dave

  10. #10
    Jedi Knight Lin's Avatar
    Join Date
    Apr 2002
    Location
    Bradenton, FL
    Posts
    946
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    4
    Thanked in
    3 Posts

    Re: Master cylinder packing pieces (shims)

    Vette,
    interesting theory. Any one else have any thoughts on this? Vette’s line of thinking would certainly explain why both masters would be shimmed, but if that were the case wouldn’t all master cylinders of this type irrespective of car maker be sold with these shims? I would like to understand this one.
    Lin
    1959 AN5 Bugeye - now with my son 😀
    1960 BT7 3000 MKI
    1987 Alfa Romeo Spider Quadrifoglio

  11. #11
    Yoda steveg's Avatar
    Join Date
    Sep 2007
    Location
    Altadena, CA
    Posts
    3,755
    Thanks Thanks Given 
    90
    Thanks Thanks Received 
    142
    Thanked in
    121 Posts

    Re: Master cylinder packing pieces (shims)

    Dave,
    Was questioning the idea that adjustable pushrod setup won't work in the Healey.

    Bought my car in '99 and it had one of the cylinders with adjustable clevis; I added another Pegasus and bought a clevis from a local hardware store. Not knowing better, I adjusted both so there is a little play before the piston is engaged. Never had any problems.

    According to Pegasus, the Girling M/C stroke is 1-3/8". I checked my clutch - and the stroke until the pedal hits the floor is 1-1/8".
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow


  12. #12
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    507
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    13
    Thanked in
    13 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by Lin View Post
    Vette,
    interesting theory. Any one else have any thoughts on this? Vette’s line of thinking would certainly explain why both masters would be shimmed, but if that were the case wouldn’t all master cylinders of this type irrespective of car maker be sold with these shims? I would like to understand this one.
    Lin
    Vette may well be right but some other thoughts.....

    Auto manufacturers put huge efforts into cost controls and it doesn't seem likely to me that they would design something that required automatically adding shims to every car if you could simply use a longer pushrod to eliminate the need for any extra pieces/labor/etc. Cost of parts and labor for shims would have caused the bean counters a fit.

    There may be other thicknesses (though Moss doesn't list optional thicknesses) but in my collection of shims gathered over the years, they are all the same roughly 1/16" thickness - if this was for internal performance of the cylinder, I would expect either a selection of shims or an adjustable threaded rod like other cars have.

    I also would expect something in the shop manual if there was a critical internal cylinder performance issue, like preventing the piston from bottoming - some directions on how to determine how many/how thick a shim to use. So, I think they set them in the factory and were never intended to be changed or eliminated, thus no mention in the manual.

    Dave

  13. #13
    Jedi Knight Lin's Avatar
    Join Date
    Apr 2002
    Location
    Bradenton, FL
    Posts
    946
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    4
    Thanked in
    3 Posts

    Re: Master cylinder packing pieces (shims)

    Steve,
    how are you measuring the stroke?
    Lin
    1959 AN5 Bugeye - now with my son 😀
    1960 BT7 3000 MKI
    1987 Alfa Romeo Spider Quadrifoglio

  14. #14
    Yoda steveg's Avatar
    Join Date
    Sep 2007
    Location
    Altadena, CA
    Posts
    3,755
    Thanks Thanks Given 
    90
    Thanks Thanks Received 
    142
    Thanked in
    121 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by Lin View Post
    Steve,
    how are you measuring the stroke?
    Lin
    Measured the length of the scrub mark on the pushrod at 1-1/8".

    screenshot.1898.jpg screenshot.1897.jpg
    At rest -vs - Pedal to the floor
    Last edited by steveg; 09-16-2019 at 02:28 PM.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow


  15. #15
    Member
    Join Date
    Dec 2012
    Location
    Tamworth
    Posts
    44
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    2
    Thanked in
    2 Posts

    Re: Master cylinder packing pieces (shims)

    The parts book lists shims for both the clutch and brake pedal. Two shims (top and bottom) for the brake pedal and "as required" for the clutch pedal. This seems to suggest the brake pedal actually requires the shims and the clutch pedal only requires shims to match up with the level of the brake pedal. Just a thought.

    Regards,
    Greg

  16. #16
    Luke Skywalker vette's Avatar
    Join Date
    May 2002
    Location
    Pa.
    Posts
    1,711
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    13
    Thanked in
    11 Posts

    Re: Master cylinder packing pieces (shims)

    I think the use of the shims by the factory fits right in with the thinking at the time. Remember that Donald Healey built this car to race and rally. He built it light and cheap. He didn't know he was going to go into partnership with Austin when the car was laid out. This car is NOT what i call a purpose built car. It was built by using production parts from any sort of manufacturer that Donald could find. Something on the order of what Shelby did with the AC/Cobra. So the original master cylinders fit. The pedal geometer got laid out and the cheapest way to get the travel of the push rod right so as to ensure that the system would not fail or bind was to shim the master cylinders. A lot cheaper than mocking up an adjustable rod with clevis. Also another scenario could be that when Healey built it, there were no shims. The Austin started manufacturing it and while on the line it was discovered that there could be a potential problem here.... so the easiest and cheapest fix was shims.
    About TV Shows-
    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

  17. #17
    Yoda HealeyRick's Avatar
    Join Date
    Apr 2004
    Location
    Massachusetts
    Posts
    5,792
    Thanks Thanks Given 
    16
    Thanks Thanks Received 
    36
    Thanked in
    32 Posts

    Re: Master cylinder packing pieces (shims)

    Quote Originally Posted by vette View Post
    Also another scenario could be that when Healey built it, there were no shims. The Austin started manufacturing it and while on the line it was discovered that there could be a potential problem here.... so the easiest and cheapest fix was shims.
    I'm kind of liking this theory. The Moss catalog doesn't show the master cylinders being used in any other British cars other than the 3000, nor is the pushrod. That makes me think they were mmade for the Healey and not an off the shelf item. If that were the case, a post-design fix would make sense. I know the bottom spacer can be a bit fiddly to install, always dropping down when I try to install the M/C so I can't see it being designed that way. Kind of an interesting brain teaser.
    Rick

  18. #18
    Jedi Knight Lin's Avatar
    Join Date
    Apr 2002
    Location
    Bradenton, FL
    Posts
    946
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    4
    Thanked in
    3 Posts

    Re: Master cylinder packing pieces (shims)

    Vette,
    Following your thinking, which problem were they then trying to solve? I am guessing (and that is all that it is) that the shims on the brake pedal were used to adjust the height of the brake pedal relative to the accelerator pedal. I suppose then that the shims could be used - or not - to adjust the clutch pedal height to the brake pedal. Probably a little less a concern than the relationship of pedal height for the brake and accelerator pedals.

    Alternatively, they may have been trying to solve the problem of the piston travel in the cylinder - but if that is the case, wouldn't the shims have been specified for use for both pedals rather than optional for the clutch? I certainly don't know. I guess we will never know definitively.

    What I do know is that like Rick said the bottom shim is a pain in the a__s to install - as if it wasn't hard enough just getting to the masters!

    Lin
    1959 AN5 Bugeye - now with my son 😀
    1960 BT7 3000 MKI
    1987 Alfa Romeo Spider Quadrifoglio

  19. #19
    Luke Skywalker vette's Avatar
    Join Date
    May 2002
    Location
    Pa.
    Posts
    1,711
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    13
    Thanked in
    11 Posts

    Re: Master cylinder packing pieces (shims)

    I don't know that I can attest that the shims can be used to adjust the height of the pedals. I have shims on both my masters and my pedals are even. It seems to me that there is enough play in at least the clutch pedal that it would take a lot of shims to effect the height of the pedal. Granted I may have some play in my metal pieces but I don't think very much if any because I would have checked that when I first assembled the car which although years ago wasn't that many miles ago. The play in my clutch pedal is all in the movement of the rod. So the shim only effects how deeply the rod moves into the cylinder. I remember some years ago I did remove the shims on the clutch master cylinder to see what it would do. It had no perceivable effect so I replaced them as they were. I believe the master cylinders will work without the shims but maybe at the time Austin was building the cars it was considered close to it's operating tolerance, ( too much penetration into the cylinder) so for safeties sake they installed the shims. I know Moss list the shims for both the clutch and the brake but I am not aware of what the shop manual says. I do know that the shop manual is fraught with omissions so ......
    About TV Shows-
    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

  20. #20
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    507
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    13
    Thanked in
    13 Posts

    Re: Master cylinder packing pieces (shims)

    So, I'm gonna try again, because I don't think what I've been saying is being heard and some of what I've read doesn't make sense to me. I am currently restoring a BT7 and just a month ago installed the pedal box and masters (new masters and new pushrods and new clevis pins) - when I installed both without shims, the clutch pedal was 3/16" high compared to the brake so I put shims under the clutch master and the pedals are now even. This is why it's fresh in my mind so I took some pictures to help explain what I mean.

    First, Steveg said in post #11
    "
    Not knowing better, I adjusted both so there is a little play before the piston is engaged." I think you may be remembering another car or your pedal box has been modified because
    there is no stop in the pedal box or pedals, they can swing as far up as you might want (they do sort of run into the return springs when lifted real high but it's not any kind of positive stop). The only stop for upwards movement is the washer and snap ring in the master that keeps the pushrod and piston inside the master. So, the pedal return spring pulls against the snap ring and washer (stop) and the only 'play' is between the stop washer/snap ring and the piston in the bore. So there is nothing to adjust to - if you have a threaded pushrod and keep turning, you will just keep raising the pedal height (or lowering it depending on which way you are turning it). Here is a picture a spare pedal box out of the car with a brake master in place and hooked to the pedal - you can see the clutch pedal is free to swing waaaay up from where you would want it - there is no stop on either pedal. (I have 4 of these pedal boxes and they are all the same)
    IMG_2438.jpgIMG_2439.jpg

    Second, Vette said in post #19
    "
    It seems to me that there is enough play in at least the clutch pedal that it would take a lot of shims to effect the height of the pedal."
    Again, the shim is 1/16" and the distance from the fulcrum to the clevis is approximately 2 3/8" for the clutch and 3" for the brake and the distance from the fulcrum to the center of the pedal pad is 11". So a disclaimer: I am not good at math, but this clearly is more than 3:1 ratio, thus .062 x 3 = .187 (3/16") or more so a 1/16" shim would mean at least a 3/16" or more pedal height change. Someone with better math skills would be able to say exactly what the clutch is vs brake... but that's not me.
    IMG_2444.jpgIMG_2447.jpg

    So, obviously I haven't read any factory literature about them so can't cite a source but just because Moss shows something doesn't always mean they are right either .

    Dave
    Last edited by red57; 09-17-2019 at 03:38 PM. Reason: typos

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •