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Supreme Being
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Last Login: Wednesday, February 01, 2012 7:08 PM
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| Hello all, One of the few deviations from stock that I made on my 56 Merc as I restored it was to add a dual master cylinder with a 7" dual diaphragm power booster. The car is just recently completed but in moving it around I find that the brake pedal has little travel and is rock hard. That's all good but the car stops poorly and the pedal does not feel "boosted" at all. All brake components are new, the engine makes good vacuum. The vacuum source for the booster is the nipple at the base of the carb facing to the rear and I have used 1/2" hose to connect to the booster. The valve that the hose hooks to on the booster works correctly . I was wondering if an incorrectly adjusted push rod (between booster and master) could cause this conditions ? Any ideas or thoughts are welcome. Pete
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Supreme Being
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Last Login: 2 days ago @ 8:07 PM
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First of all, vacuum should be manifold vacuum, not venturi(carb) vacuum. Different type of signal. Secondly, do you have play in the rod going from off the brake pedal to the booster.
54 Victoria 312; 27T 255 Flathead, 48 Ford Conv 302, 56 Bird
Forever Ford
Midland Park, NJ
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Supreme Being
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Supreme Being
Group: Forum Members
Last Login: Wednesday, February 01, 2012 7:08 PM
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| I will reattach the hose to manifold vacuum to see if it makes a difference. The vacuum at the large port at the rear of my Holley 1850 is full time not ported but I take it that there is not enough volume at that location to operate the brakes? These are all new parts ( booster and master) and the push rod is adjustable. There is play between the brake pedal and the booster And you are correct the pedal feels no different with the car running than when it is not as in no boost
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Supreme Being
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Supreme Being
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I don't want to clog up the diagnostic conversation but my first question would be, were the brakes fully functional before the addition of the master cylinder/booster? If so, how much vacuum is your engine making at idle? Then, if the vacuum is adequate, is the power booster a used/new or rebuilt unit with a check valve?
Mark Hebard
57 Black Tbird 312/auto
65 Galaxie 500 2drhdtp 352/Cruiso
66 F100 Custom Cab ShortyStyleside 390/C6
Monterey Bay, California
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Supreme Being
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Last Login: Wednesday, February 01, 2012 7:08 PM
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| Bingo, my set up came from oldIrishDave. I have been in touch with him and it is he that suggested push rod length. To me it feel like a dead booster. The pedal feels like a block of wood, otherwise the brakes work just fine
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Supreme Being
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Forum Member
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| Hi Guys; Glad this came up. I'm looking to replace my old original master cylinder to a double pump master cylinder. Can anyone tell me what would be the best? I won't be using any booster, just the basics, and does the front valve go to the front brakes and the rear to the rear? Advanced thanks. ------------------------------------------------------------------------------------------ Old Y Block
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Supreme Being
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| Be sure and check for vacuum leaks. I have a friend that just had the same problem, was missing the rubber cap from one of the vacuum ports. Replaced the cap and problem was gone. I used the same booster from old Irishman's and it works great. Mike http://www.y-blocksforever.com/forums/Topic37961-3-1.aspx?Highlight=brakes
1956 Fairlane Victoria (ORREO)
Overlooking Beautiful Rimrock AZ
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