master cylinder bore

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ronw

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What size bore M/C bore do I need for 68 dart big block with manual front disc and 2 1/2 x 10 drum on the rear? I'm using an adapter plate in order to use the new aluminum style M/C. I'm looking at auto zone NM 1822. Thanks ron
 
I'm running a similar one (1.032" bore) on my Dart with manual disc's ('74 & later style calipers) and drums in the rear. It works fine. I have no problems stopping.
If you're running the early style calipers I'm not 100% certain that it will work.

Ted
 
15/16" on my Duster. Stops well and I like the pedal feel. Had manual brakes on my old Mirada and they were hard as a rock.... hated that, but can't remember what bore mc was on it.
 
1968dartman said:
You want either 3/4 or 7/8 at the most for that setup.
Click to expand...

From what I understand the small bore masters (under 1 inch) were for power brakes and the larger ones are for manual brakes. That's what I have seen in some parts catalogs.
 
^^Intuitively, that seems backwards. Smaller bore= better braking with less foot pressure^^
 
But with more pedal travel. More travel is easier to modulate, making smooth stops easy, and keeps the passengers from getting whiplash. I have a 15/16, but with a booster, and I love it.
 
Dr. Diff sells the newer lightweight m/c's with a 15/16" bore. That's what I run on my duster, but I'm running dr.diffs 13" front disks and 11x2.5" rear drums.
 
Manual brakes you want a smaller bore. 7/8"-1". I have a brand new Wilwood 7/8" bore master for sale if you're interested, pm me.
 
Well I'm wise enough to know when I might be wrong and this is likely one of those times. So I'm going to switch to a smaller bore master. I'm curious to see if there is an improvement.
I did some searching and I found an aluminum body unit with 15/16" bore.
http://www.summitracing.com/parts/dhb-m39476
That master has 3/8x24 threads so here's the adaptor fittings if you've got the larger fittings on your lines like I do.
http://www.summitracing.com/parts/dhb-m39476

Ted
 
My Dart has four wheel disks and I ran the factory ( I think 7/8") until it started leaking. It was replaced with a 1 1 /32" and I hated it, the pedal was like pushing on a concrete floor and the car didn't stop as well. So I replaced it with a Dr Diffs 15/16" mc, it stops a ton better but not as well as the factory 7/8" mc. I wish the good doc made one in 7/8".
 
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