Upgradng brakes to dual reservoir master cylinder

Early C Bodies - The Slab Side Years

  1. BillGrissom

    BillGrissom Active Member

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    Apr 23, 2011
    Sacramento, CA
    While replacing the booster in my 65 Newport, I decided to upgrade to a dual reservoir master cylinder, which was standard ~1968+, per federal mandate. It is considered safer since the front and rear brakes are on separate circuits, and hopefully you will notice when one side fails. Later cars had an "imbalance switch" to sense such failures. You can get those as part of an after-market "combination valve" (~$80). I have one from a 1968 Satellite I might plumb in someday. BTW, the latest cars use an X-pattern dual system where each reservoir operates a front & rear wheel. That is better since hard to stop on rears alone.

    The booster shown was listed for my car on rockauto, at a great clearance price of $70. My original booster was a Midland-Ross (V-band clamp). I stored the new single-pot MC that came with it for museum use. You can get 4-bolt dual MC's that bolt direct, but I prefer aluminum for less weight and corrosion. Those are all 2-bolt, so required a $35 adapter plate (Dr Diff on ebay). Many people use an 80's Dodge truck MC, but mine is from a ~95-99 Breeze ABS since I used that on my Dart and Valiant and got cheap (~$25). The ABS version has just 2 ports, as we need. Even newer MC's mostly have bubble-flare ports instead of inverted flares (like 1965), but you can make bubble-flares with your "double flare" tool (youtube). The MC bore is 7/8"D vs 1"D for the original, so the pedal will be easier but travel more. That could help if I install front disks some day.

    I re-used my "distribution block" by plugging the rear port (3/16" inv flare plug) and putting a 1/4" to 3/16" inv flare adapter in the top port. I attached the new rear tube from the MC to the existing rear tube using a 3/16" inv flare coupler. You can find all in bubble packs at Autozone (their adapter incorrectly says "NPT"). Do not install a 3/16" tube in the top port, even with a nut that fits, as it will not seal on the 1/4" inv flare. You could also use a 3/16" inv flare tee. I don't know why my factory distribution block was unsecured. I am guessing it is original. I see no holes to mount it. Was the assembly line running too fast that day? The right front tube crosses over at the front instead of on the firewall like in my A's, which I expect is factory. I bent and flared the new 3/16" tubes myself, using leftover tubes.

    alum MC.jpg

    Distribution block.jpg
  2. commando1

    commando1 Old Man Wearing a Hat on the Porch FCBO Gold Member

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    Mar 10, 2011
    FUHOA Reservation, Sebring, Florida
    The nice part of your post is that so many people go to AutoZone and say " I need <fill in the blank>" to a complete freakin idiot.
    They expect everything in one box plus free installation.
    And they learned nothing.
  3. Catfish

    Catfish Senior Member

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    May 3, 2013
    Baker, MT
    I still cannot decide what master and booster to run. Seems everyone has a different opinion and they all seem to work. Nice write up.
    Last edited: May 14, 2013