1. Boiler_Gawd

    Boiler_Gawd New Member

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    Hello

    My first thread

    I have a 1968 Monaco 500 Convert. i just want to ask the guys who have converted from Power drum brakes to Power disc brakes, have any of you been able to lock up your front brakes or just the rears... I may expand on this as answer come in ..
     
  2. traintech55

    traintech55 Senior Member FCBO Gold Member

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    If you did the installation correctly, you should never be able to lock up disc brakes unless you are on ice.
     
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  3. mopar440

    mopar440 Active Member

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    Or didn't install the right proportioning valve, or a incorrectly adjusted universal one
     
  4. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    Also, did you upgrade to a disc brake booster? It makes a difference in braking performance as the disc booster has about 25% more boost. As noted above, discs should not fully lock up.

    Dave
     
  5. Boiler_Gawd

    Boiler_Gawd New Member

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    IMG_20200405_172227.jpg Hi everyone!

    Booster has been upgraded , 8" Leeds dual diapharam , KH pin calipers , Wildwood valve in the back drums
     
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  6. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    Nice clean looking installation. Are you having braking issues, or are you just curious? For the record, 8" dual diaphragm boosters were common on B-Bodies, the are a little lighter in terms of boost capacity than the 9" units usually found on C-Bodies. A C-Body is significantly heavier than a B-Body and hence the larger booster. The GM master cylinder should work fine as long as the bore size is the same as a Mopar unit.

    Dave
     
  7. Boiler_Gawd

    Boiler_Gawd New Member

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    I am finding I can't lock up the front brakes. , But that can be from uneven pad contact on the rotor ,as everything is brand new, I might let it bed in a little and see what happens , plenty of brake for general driving , just was wondering if anybody else can lock up the fronts as I can't yet , the bore is 1-1/8"
     
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  8. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    You can get a longer pedal stroke with increased clamping power to the discs with a 1" bore master cylinder which was typical of many Mopars of that era.

    Dave
     
  9. Boiler_Gawd

    Boiler_Gawd New Member

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    Hey Dave

    I was under the impression in 1968 they had a 1-1/8 " bore
     
  10. traintech55

    traintech55 Senior Member FCBO Gold Member

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    Please go back to post #2. You should not be able to lock up disc brakes.
     
  11. CBODY67

    CBODY67 Senior Member

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    Usually, do NOT try any max-effort braking with new brake pads/rotors. Do the bedding-in first (there is a procedure of many stops, from differing speeds and decal rates). It's about getting the surface of the discs polished and also curing/cooking-out the resins in the pads themselves. How "rough surface" the discs are (or are refinished to) can lengthen the process a bit, too.

    USA vehicles were typically biased such that the rear brakes would lock-up first This still allowed for steering control as sliding rubber can't generate forces to change direction of the vehicle. Seems like the Chevy Citation was the first GM car designed to lock the front brakes first?

    Disc brakes need more pressure to operate well. The smaller dia master cyl would give more "hydraulic leverage", usually.

    CBODY67
     
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  12. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    The '68 had a 1" with standard disc brakes and a 1 1/8" with power discs. Trick is that the 1 1/8" ran behind the 9" booster and I suspect that there will be a performance difference as a result. Be sure that the portioning valve is properly adjusted. Some of the hot rodders are using the 1" Mopar drum brake master cylinder to boost braking performance, but I do not think that is a particularily good idea because of the smaller reservoir on the drum unit. In any case you do not have that option with an after market booster. www.summitracing.com has a variety of two bolt master cylinders, you might be able to use if the problem can not be corrected any other way.

    Dave
     
  13. Boiler_Gawd

    Boiler_Gawd New Member

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    Fluid displacement is not an issue, but will leave it a little longer and see what happens,

    Just a side note, talked a few Mechanics, and they told me you should be able to lock up the fronts in a emergency situation....