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  1. #1
    Join Date
    Oct 2008
    Location
    Near Gainsborough
    Posts
    75

    Brake vacuum booster AK Gen 1

    The brake performance of my car is adequate, but requires a heavy pedal pressure. The engine has quite a high lift roller cam, hence little engine vacuum assistance at the servo, I was wondering if anyone has had the same problem and how they got round it? I have a spare groove in my crankshaft pulley, so I could run an engine driven vacuum pump off something else, or there are electric pumps that switch on when needed to boost the vac. I would be grateful for any advice, TIA, Mick

  2. #2
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    1,742
    Have you seen what vacuum you are pulling at idel . The overlap will determine the vacuum. If your in the low teens at idle you might struggle below 10.

  3. #3
    Join Date
    Oct 2018
    Location
    Shipston-On-Stour
    Posts
    733
    On my cobra the idle vacuum is low but the servo does work OK. On my GT40 build I have opted for an electric vacuum pump. Bought on EBay, not tried it yet but it will hopefully work! Car Builder Solutions also do them. They are quite noisy apparently but then so is my Holley fuel pump!
    Might be worth checking your servo before investing and going to the trouble of fitting it all
    Dax with 1964 Dual Quad 427 and Toploader box

  4. #4
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    60
    Posts
    2,522
    Many diesel cars have a vacuum pump built into the alternator; so there's another idea.
    Cheers

    Myles D-W

  5. #5
    Join Date
    Jun 2014
    Location
    Swansea
    Age
    57
    Posts
    163
    I have an AK and have had no trouble with the brake servo and I have an MC1 cam, the vacuum at idle is about 15 to 18.

    However, I have recently but a remote servo on to help with a heavy clutch pedal and to help with the vacuum I have put a vacuum reserve tank in between the manifold and the remote servo. The clutch is nice and light now. A vacuum reserve tank may help with the brake servo. I bought mine from amazon https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1 .

    Hope this helps.

    Rob
    Rob

    AK Gen I - 4.6l Rover V8, Stage III heads, MC1 cam
    On the road March 2019

  6. #6
    Join Date
    Oct 2008
    Location
    Near Gainsborough
    Posts
    75
    Thanks for all the advice and suggestions. I do not know what actual vacuum I am pulling at idle, I just know it is a high lift roller cam with some overlap, so I expect it will be quite poor. Next time I have the car running I will try hooking up my vac gauge and see what it actually is and maybe have a look at the servo too. Cheers, Mick

  7. #7
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    759
    Is your idle vacuum going to be a problem even if it is low?
    The servo should act as a vacuum reservoir and presumably the vacuum will increase when RPM increase (even if the engine stops you should still have enough vac' for a couple of stops) during braking with a running engine the engine would most likely be on overrun and pulling good vacuum levels.
    Mine does not pull great vacuum at ilde but my, newly deployed, servo seems to work well, althoguh I reserve the right to change my mind on that at any future date!

  8. #8
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    60
    Posts
    2,522
    The first simple test is to buy a length of hose and attach the servo to another car - see it the brakes feel any different.
    Cheers

    Myles D-W

  9. #9
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    759
    Quote Originally Posted by mylesdw View Post
    The first simple test is to buy a length of hose and attach the servo to another car - see it the brakes feel any different.
    Wouldn't that be difficult and possbly dangerous to do, even with a long lenght of hose?

  10. #10
    Join Date
    May 2016
    Location
    Cheshire
    Age
    52
    Posts
    435
    Quote Originally Posted by GDCobra View Post
    Wouldn't that be difficult and possbly dangerous to do, even with a long lenght of hose?
    Not on a dual carriageway.
    ~~~~~~
    Sumo Mk3

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