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By petew - 15 Years Ago
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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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By paul2748 - 15 Years Ago
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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.
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By oldcarmark - 15 Years Ago
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Is the booster setup new or used?What are you using as a pushrod-an adjustable length one or the stock one?As Paul mentioned you need manifold vacuum.If there is no outlet on the manifold for a fitting you may have to drill and tap for one.It sounds like you are getting no "power boost" for sure.Power brakes with non functioning booster will give a harder pedal than the non boost original setup.One more question would be are the wheel cylinders moving freely(not stuck seized?)
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By petew - 15 Years Ago
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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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By oldcarmark - 15 Years Ago
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If you have a fulltime vacuum source the booster should work.Have you tried adjusting the pushrod longer so there is less freeplay?My friend with a 54 Mercury added the booster kit to his and couldnt get it to work properly.After playing with the length of the pushrod and gradually making it longer he got it working properly.I assume there is a check valve on yours where the vacuum hose attaches to the booster?I have installed a similar dual master and booster( and disc brakes) on mine as part of my winter project.I have bled the brakes but because the motor is out I have not been able to see how this new setup works.I have added an adjustable proportioning valve and I know once I get it running I will have to spend some time sorting out the booster setup and adjusting the brakes.One last suggestion regarding your booster-it is possible you have a defective unit.The guy I bought mine from in the US told me he had to replace one recently because it was defective out of the box.I dont know where you bought yours but i got mine from "the old irishmans auto" who sells these setups on Ebay.
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By MarkMontereyBay - 15 Years Ago
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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
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By petew - 15 Years Ago
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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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By oldcarmark - 15 Years Ago
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OK So try that and let me know if that solves the problem.Might help me get mine setup better when the time comes.One thing I did on mine that you might consider doing.I drilled a second hole in the pedal about an inch lower than the stock one which lowers the pushrod end and makes it straighter going into the booster.I find the angle of the pushrod almost rubs on the firewall installed as is without the second hole.I also used a rubber floorplug from Dennis Carpenter which is exactly the right size for the hole in the firewall.Cut a hole in the centre and cut some slots radiating out from the centre.The pushrod goes through it and it provides at least some sealing rather than just having a hole there.
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By Old Y Block - 15 Years Ago
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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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By YellowWing - 15 Years Ago
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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
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By paul2748 - 15 Years Ago
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Old Y Block (3/3/2010)
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.
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Old Y Block
Drum brakes all around? If so, 65-66 Mustang is one that may work ( I think this is a dual master).
Discs in front? Most any later Ford with disc and MANUAL brakes. 75-80 Granada for one. Not sure if master bore is compatible
If drum brakes all around, does not make a difference which reservoir goes to where. If disc's, the larger reservoir does to the front (disc) brakes.
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By oldcarmark - 15 Years Ago
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If you dont mind I would like to make a suggestion regarding changing to a dual master cylinder.My buddy with a 55 Customline and all drum brakes put one of the booster/master cylinder kits on his and its like night and day as far as improved braking.If you are going to redo the lines to go to a dual master why not consider installing one of the booster kits?About $150.00 for new master and booster.Just a suggestion.
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By shakey pete - 15 Years Ago
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hi with the engine not running pump the brakes to exhaust all assist hold pressure on the brake peddal and start the engine if the peddal doesn,t drop you have no vaccum assist then you can try to find out if its lack of vaccum or the booster  shakey Pete
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By petew - 15 Years Ago
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Got it straightened out. My vacuum line was pinched and the push rod was out of adjustment (to short) . Adjusted that , fixed the hose and I have power brakes. Mind you it doesn't stop like my 2006 pick up but for 2 tons plus with drum brakes it's ok. I measured 20" of idle vacuum from my vacuum source at the 1/2" nipple located at the base of the carb and it seems to do the trick just fine. Thanks for all of your input. Pete
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By oldcarmark - 15 Years Ago
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Glad to hear it works.Now its time to add disc brakes to the front!LOL
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By petew - 15 Years Ago
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You know, I considered adding disc brakes but haven't seen a kit that maintains the 5 on 5 bolt pattern. Most are 5 on 4.5 . Guess I'm just being picky
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By Philo - 15 Years Ago
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Old Y Block (3/3/2010)
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 You didn't mention what body you're running but I'll tell you that I used a '67 Falcon drum brake dual reservor master cylinder on my '57. Bolts up to the two lower holes on the firewall. (Put bolts in the upper two now empty holes). I used the original pushrod and relocated the stoplight switch to the now unused opening on the original brass tee fitting on the frame rail. Both reservors are the same size, looks good and works great. The line for the front brakes goes to the rear reservor. hope this helps.
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By Old Y Block - 15 Years Ago
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Thank you for the reply. I want to put the duel master cylinder on a 55 Fairlane. I will look for a 67 Falcon master cylinder and give it a try. Thanks to all. Old Y Block
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By oldcarmark - 15 Years Ago
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Is mercury bolt pattern the same as my Fairlane?Anyone know?
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By PWH42 - 15 Years Ago
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Mark........I'm pretty sure the Merc wheels are 5 on 5,where your Ford is 5 on 4.5.
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By Frankenstein57 - 15 Years Ago
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Old car mark, glad I found your post. I am finishing up a 58 ranchero 292 for its maiden voyage, I have a similar problem. I am using a dual master with a 7" booster, I bought the setup from gearheads several years ago (bad experience), when the time came to install it the booster was broken where the rod comes out. Rather than try to deal with these people,I bought a replacement from speedway motors. I'm running Torino disc brakes on the front, stock drums on the rear, all parts new. I have the same feel, pedal is rock hard, no power assist feel. I'm moving the car around and I'm afraid I'm going to go through the shop wall.I also have an adjustable proportioning valve. I'll check the things mentioned in this topic and hopefully find the gremlin. By the way, the torino spindles are a good disc option for the 57,58 cars, I did have to mill 3/8" off the upper a arm cross shaft to get my camber back. Same spindles on LTD 2's, montegos, ect. Mark
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By Frankenstein57 - 15 Years Ago
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I think my hard pedal,no stop was due to some of the chinese fittings I plumed the system with. Repaired a couple of leaks and re-bled the system, should be ok. As far as milling the cross shafts on my a-arms, it might not be necessary with the torino spindle swap. Ford calls for 1 and1/2 degrees positive camber, we were shooting for 1/2 degree negative.
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