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Technical Master Cylinder Advice Needed

Discussion in 'Traditional Hot Rods' started by Steve Lowe, Jan 1, 2020.

  1. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    The way things are going down here, I wish I were Canadian. Is that why the outlets on your master cylinder are on the wrong side? Lols!

    Thanks for checking. My current adapter is 81 mm. Not perfect, but perhaps with a little modification? I can just make another adapter as well.
     
  2. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Without a Booster try an AC Delco #18M309 Master cylinder [24mm] or slightly over 7/8 bore
    This is a stepped bore M/C from an S10
    The 24mm bore should be small enough to get good brake clamping pressure without a booster
    The ports are on the LH side
     
  3. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    I'm glad to hear that! I've become a bit paranoid after failing at my 1st mc swap attempt and reading so many confusing stories. I guess, "Nothing ventured, nothing gained" RustyHope gets good reviews on P15D24 site. I like his setup using in-rotor hubs. The only thing bothered me a little was that you have to modify the steering knuckle and steering arms. Did that go easily?
     
  4. Tri-power37
    Joined: Feb 10, 2019
    Posts: 510

    Tri-power37
    Member

    Here is a list of masters used by g body Malibu’s that convert to manual brakes and different masters they use to get it done . The one in the picture is dodge shadow I believe. The one I use isn’t on the list because they discovered it later . Good news some are dodge.
    66CDEFEC-B4A5-4ED3-A138-562A1A91E992.png
    A9304DED-2610-4DC2-991F-0816F65D54EA.png


    AF4EB0AA-1309-4CD6-8FC6-FE3F50BA4DCF.png
    ABB2901E-720F-4C4E-9F59-B0979063448B.png
     
  5. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    1998 s10 mc's on Rockauto are listed as a 1"bore dia. Would a "step bore" be listed that way?
     
  6. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Parts suppliers don't even know what a stepped bore or quick uptake M/C is [they only know part numbers on a computer]

    The one I suggested was an earlier S10 with LH ports. designed for 4 cyl s10's without a booster.

    They also have another M/C for boosted brakes "ACDelco #18M310" this also has a working bore diameter of 24mm [7/8"]
    But the difference is the stepped bore or quick uptake bore has been increased to 36mm [non boosted M/C's have a quick uptake bore of 31.75mm]

    You get clamping pressure from the 24mm working bore but pedal travel is reduced by the 36mm or 31.75 quick uptake bore.



    These stepped bore M/C's are now starting to creep into historic road racing with normal calipers.
    They are really reassuring to have a high pedal when doing "desparado braking techniques"
     
    Last edited: Jan 3, 2020
  7. Tri-power37
    Joined: Feb 10, 2019
    Posts: 510

    Tri-power37
    Member

    The master we talked about earlier (mc390572) is not the stepped kind and can also be found by ac delco number 18m974 although they are 1 inch bore that is very close to 24mm
    1 inch is equal to 25.4 mm I don’t think the 1.4 millimetres will change things very much.
    I’ve never had anything to do with step bore master cylinders when I mix and match brake parts and I’d not suggest it as it just complicates stuff even more.
    Most times if you try and match the master bore to the wheel cylinder and caliper bore as best you can and find a compatible proportioning valve (no easy feat) it works out .
    It is a lot of mix and match.
     
  8. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    The M/C shown in your photos is hanging off a brake booster [post #15]. Steve Lowe stated that he is using a manual set-up.
    A 22mm [7/8"] M/C has a swept area of 0.6013 sq in vs a 25.4mm [1"] M/C with a swept area of 0.7854 sq in.
    The S10 22mm M/C has only 75% of the swept area of the one you suggest.
    If Steve Lowe has the Fr vs Rr balance correct [Calliper size vs Wheel Cylinders] changing to a smaller M/C wont affect the balance.

    There are plenty of threads on the H.A.M.B where the front brakes are converted from drum to discs and the pedal goes to the floor, so they change to a larger M/C and then they don't have the stopping power.

    Using a smaller diameter M/C gives the clamping /stopping power ,but the trade off is excessive pedal travel.
    The stepped M/C fixes the issue by taking up the pedal travel displacement .[near the top]
     
  9. guitarguy
    Joined: May 26, 2008
    Posts: 650

    guitarguy
    Member

    If your still by chance going to use the Cherokee master cylinder, Chrysler typically of that era (late 90's to early 2000's---I have no knowledge after that) and rearward to the 70's used the rear port for the front discs and the front port for the rear drums. I know it seems a little backwards, but many many moons ago when I was doing upgrades on non HAMB vehicles and getting cores out of junkyards (back then cores to turn in where a little expensive), I kept track because I did not know. I can not speak for any other manufacture though as it was all Mopar for me back then. Plus I was working in the Chrysler dealerships back then and was always on the lookout for parts that could be used on older vehicles.
     
  10. the oil soup
    Joined: May 19, 2013
    Posts: 277

    the oil soup
    Member
    from Tucson,AZ

    The only thing bothered me a little was that you have to modify the steeringknuckle and steering arms. Did that go easily?

    My truck is a B series so it may differ from yours but the steering knuckle/spindle only needed to be drilled and tapped for larger bolts to mount the new caliper brackets and as far as the steering arms, I had those drilled from the opposite side so the tie rod could be mounted from the bottom ( in cross section the hole is hour glass shaped ). I also had Sid's drop the axle 3" and this facilitated using dropped tie rod ends ( available through RustyHope or Speedway ). The stock drag link was built with a bend in it but I fabbed a new one that is straight with adjustable ends and is parallel to the tie rod. I also reversed the spring eyes.
     
  11. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    Yes, that's why I'm trying to find those who have had success with similar applications. Several Dodge / Plymouth truck enthusiasts support the 95 - 01 Jeep MC's. They report having good pedal and stopping ability with the 1" bore master. Of course all of this is anecdotal. Without professional testing facilities and equipment it's impossible to make accurate comparisons. I'll bet there's more than a few street rods with "upgraded" brake systems that were actually downgraded? I do see the advantage of a step bore in some applications and welcome more opinions on them. The Jeep master I have pictured and which is reported to have worked well for others is not a step bore. I'm hoping to keep it as simple as possible. DSCN2419.JPG DSCN2420.JPG
     
  12. Tri-power37
    Joined: Feb 10, 2019
    Posts: 510

    Tri-power37
    Member

    I think if others have used the 95 - 01 Jeep masters with the 1 inch bore successfully you should go ahead and try it. Sometimes it’s better to take a reasonable estimate of what might work and go for it than it is to discuss it to much
    If it isn’t optimal for you after install you can always get a smaller bore master or adjust your thinking in some other way . Or it may just work fine!
     
    Last edited: Jan 3, 2020
  13. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    Yeah, You're probably right. I could have installed 10 master cylinders in same amount of time I've spent trying to figure this stuff out. Still, it would be nicer to find a level mount master cylinder with english inverted flare connections. The Jeep master uses metric fittings and bubble flares which I don't have the tool for.
     
  14. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Steve..... This is a standard type M/C schematic
    Master+Cylinder+Operation.jpg
     
  15. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    This is a stepped bore M/C schematic [also known as a quick uptake M/C]
    Small+forward+bore+for+high+pressure+in+normal+braking.jpg

    And this is the Jeep M/C internals you posted.

    Jeep MC.JPG
     
  16. Tri-power37
    Joined: Feb 10, 2019
    Posts: 510

    Tri-power37
    Member

    Let the experiment begin? Tell us how you do.
     
  17. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    I think I understand the step bore principal? It's not easy to see in my photo, but the larger dia. piece that looks like a piston is only a seal. It goes up against a stepped down flange and can not move after the retaining ring is installed. I'm fairly certain mine is not a step down.
     
  18. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    Thanks! for all your help. I just found the exact same master cylinder that I have with a level reservoir. Of course! After I already bought this one. Lols! I tried finding just the reservoir separately, but no such luck. AC Delco 18M802.jpg Side view AC Delco 18M802.jpg
     
  19. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    AC Delco # 18M802
     
  20. Steve Lowe
    Joined: Nov 8, 2019
    Posts: 74

    Steve Lowe
    Member

    Late 90s Jeep Wranglers and Dodge Dakotas.
     
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