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Technical 1935 Ford w/power brakes question

Discussion in 'The Hokey Ass Message Board' started by gearheadbill, Jul 24, 2018.

  1. gearheadbill
    Joined: Oct 11, 2002
    Posts: 1,313


    There are so many really good mechanics here on the HAMB that I can't think of a better place to ask. Hopefully this is not so o/t that it gets bounced. I'm not looking for text book technical info; just practical. I've never had an old car with power brakes before, so this new for me.

    I have a 35 Ford resto-rod with modern power assisted brakes. The system has a small brake booster under the floor, a reserve canister between the intake and booster and working check valves. The car has a mild SBC that has 11hg vacuum at idle/in gear, 14hg in idle/park but will run up to 22hg under throttle then back to around 14hg when decelerating. My understanding is that 18+hg is needed to effectively utilize the booster.

    To my simple brain the reserve canister should store vacuum like a compressed air tank, only negative air pressure (suction) rather than compressed air pressure and the vacuum should be able to be stored/replentished. If not, what the heck good is the reserve can? The motor make plenty of 18+hg vacuum, just not all the time. Why won't the reserve canister store the highest level of vacuum?

    I hope this description makes some sense. Thank you. View attachment 3978522
    Last edited: Jul 25, 2018
    Casey Riley and chryslerfan55 like this.
  2. ford40
    Joined: Jun 7, 2009
    Posts: 94

    from pa

    Why do you need a reserve canister? there is a check valve in the booster.
  3. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,599


    those vacuum #s seem low that may be the problem.if it has mild cam should be higher
  4. 35WINDOW
    Joined: Jul 7, 2005
    Posts: 454


    Apparently you are having issues-what are they? From what I've seen, a Canister will store vacuum, but will work for only a stroke or two before it is depleted-
    I have a '35 too (with Disc brakes and a 7" dual diaphragm Booster)-my engine does not make enough vacuum either, so I went with an electric vacuum pump (a Hella UP30)-they are made for electric cars, although they are also used on Ford Mustangs (Cobras),Ford Diesel Pickups, Volvo and a host of other cars-look on Ebay under electric vacuum pumps-there are a bunch-if you do this, pair that with a regular vacuum pump shutoff switch-hope his helps-

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