Which "drag race" master cylinder?

Brakes for your Classic Mopar

  1. tnts72

    tnts72 Well-Known Member

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    Anyone using the 131323M - supposed to be for a 70 340 Duster 15/16 bore Disc / Drum setup?? I was planning to install one in my 72 when I get the 11" discs up front and the 11" dana drums out back...
     
  2. Locomotion

    Locomotion Well-Known Member

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    Not using that size MC, but the theory is the bigger the brakes and pistons, the bigger bore and volume MC is needed.
     
  3. Motopsycho

    Motopsycho 69 Darts Rule

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    heres what i run on my duster
    has the adapter plate
    85 or dodge truck
    and run dot 4 brakefluid
     

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  4. stroked340

    stroked340 FABO Gold Member FABO Gold Member

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    Seeing as i just installed Wilwood brakes i'm using their "light weight" master part #260-4894:D:D
     
  5. Johnny Mac

    Johnny Mac www.blueprintengines.com FABO Vendor

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    Just to followup. The only aluminum one I could find was actually to a fwd dodge spirit or daytona. The reservoir has a slight downhill to it. Other than that it works great. 22 bucks I think. Many of the go to apps people used to buy I have found are now mad with cast iron bases. If you just want the small one, and dont care about weight, then those would work fine. But aluminum was what I was hunting for.
     
  6. furyus2

    furyus2 Well-Known Member

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    I have the 73 up A body disc brake setup on my 64 Sport Fury. Upgraded to the larger 11 3/4 rotor. Didn't stop very well. Went to the 76 up Aspen calipers, which are larger than the A body. Can't remember the exact size. No brakes with a 15/16 bore. Went to a 1 1/32 bore MC. Stopped much better. So calipers bore size is important. I also went with smaller bore rear wheel cylinders. That helped too. Sometimes you have to do a little trial and error.
     
  7. ir3333

    ir3333 Well-Known Member

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    a 1/16" inch increase in master cylinder bore size requires a 12% increase in leg for the same pressure
    a small 15/16" master and a 'cuda 2 3/4" caliper piston will stop effortlessly,almost like power brakes.
    ..if you go from 15/16 master to 1 1/16 you will require 24% more leg
     
  8. ir3333

    ir3333 Well-Known Member

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    Exactly backwards
    smaller master increases pressure but increases pedal travel .
    15/16 bore master and 2 3/4 piston (cuda caliper ) on an a body will stop effortlessly
    1 1/8 bore master and 2 5/8 piston (a body caliper) will make stopping very difficult
     
  9. ir3333

    ir3333 Well-Known Member

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    a 1" master with 100lb of leg will produce about 3600 psi with the a body 2 5/8 caliper
    a 1' master with 100lb of leg will produce about 4400 psi with the e body 2 3/4 caliper
    a 15/16 master will increase the pressure even more but there will be a bit more pedal
    travel.
    use the small master and larger disc caliper and you will have great brakes.
     
  10. inertia

    inertia Well-Known Member

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    ^^^^^^ Xs2.....
     
  11. turbofreek

    turbofreek batcrap crazy racing team

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    you guys make me sweat here. ive got wilwood on all 4s and the larger wilwood mc 1.19 no power booster. all is brand new not even filled with fluid yet. i am about to in the coming days or weeks bleed them and see how it works. am i gonna need to stand up on the pedal to get brakes to stop? should i go down to a smaller mc before even trying the big mc? very fast drag rwving but also a street cwr that will see lots of street miles on weekends.
     
  12. Johnny Mac

    Johnny Mac www.blueprintengines.com FABO Vendor

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    Mine is listed in metric. Just a sliver over 1 inch. Wilwood fronts. Wouldnt want it any stiffer.

    MC before this setup was the 1.125 with factory style disc. Again pretty stiff.

    Both stop the car fine at the track. Would I want to take a 500mile road trip? No.

    That being said....try what u have. I have rear drums. Dont use these opinions to take your setup apart...it may be just fine for your liking.
     
  13. BillGrissom

    BillGrissom Well-Known Member

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    First, I don't get all the "stops good" or "didn't stop good" due to a different MC. Tires stop the car and brakes stop the tires unless they overheat (drawback of drums). The MC just makes pressure. So, these guys must be talking about "pedal effort required to make a certain pressure". A smaller bore requires less pedal effort, at the expense of more pedal travel (depends on sponginess of hoses, air bubbles, slightly fluid compressibility).

    If you use a 4-2 bolt adapter plate ($30 ebay), you can use many MC's. I use one for a 95-99 Breeze (w/ ABS) on all my old Mopars. It has 7/8" bore. Many here use an 80's truck MC (post 28 ), or buy the same PN for 2x price at speed shops. Don't go too new or you must deal w/ "bubble flare" ports. Also plumb an adjustable proportioning valve in series w/ the rear tube.
     
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