Ironracer
Gearhead
what would be a better M/C hole? Car is a 74 Duster, factory power disks, and rear drums? I have an original push rod ..converting to manual...the 15/16" ? or the 1and 1/32"?
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Master Cylinder Bore?
- Thread starter Ironracer
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Ironracer
Gearhead
That's what I was wondering I can't stand the feel of the friggin Factory power brakes... most of my rides when I was younger were manual brake steering and trans
Ironracer
Gearhead
So the 15-16" gives you more pressure?
One gives more pressure, one gives a better pedal feel. I can never remember which.
Yes, gives you more leverage by not having to push so much fluid at one time.
Gives just a little bit longer of a stroke on the pedal.
Like the Lever and The Fulcrum
The closer you put the Fulcrum (small rock) to the Big Rock, the less effort it takes on your part to do the work.
The Lever stroke increases more as you move the fulcrum closer to the big rock.
Same theory with your manual brake system.
Ironracer
Gearhead
As a Carpenter, i was doing stuff back in the day, still do, with bottle jacks and 2x4s removing bearing walls and opening up 2nd stories w/ roof loads. when i first started framing, we were using string lines and water levels. However my pointy little narrow mind, is having a hard time directing leverage in a location and = that to volume and pressure of a brake hydraulic system! Lol duh
Had a '69 Satellite Drum Drum Car. Master cylinder was the 1 1/16th, swapped it out for the 15/16" bore master.
Huge improvement, the larger bore master the brakes would grab quick and the pedal was hard to push.
Swapped over to the 15/16" bore master, now I had a lot more control over when the brakes would come on, I could easily feather them without them grabbing hard.
Then the nice part it was much easier to push the pedal, much more of a pleasure to drive. Just felt way safer too, felt like I was in much more control of the car.
Huge improvement, the larger bore master the brakes would grab quick and the pedal was hard to push.
Swapped over to the 15/16" bore master, now I had a lot more control over when the brakes would come on, I could easily feather them without them grabbing hard.
Then the nice part it was much easier to push the pedal, much more of a pleasure to drive. Just felt way safer too, felt like I was in much more control of the car.
Ironracer
Gearhead
I did the 1980 FM J swap on my 66 satellite and kept it manual and I used a master cylinder from a 71 Challenger they worked pretty damn good I liked em
The bigger bore master is often used or suggested for the drag racers. More pressure sooner to help with high speed slow downs. But as mentioned, your pushing more fluid which is harder to move since it doesn’t compress.
Ironracer
Gearhead
10-4 on that! Thank you Rumble Fish! I'm interested in the most performance from my car, and I'm thinking about jumping up the 11.75 disks
....one day, eventually. So I probably get more driving pleasure, Hehehe, from the smaller bore? By more " Feel"?
I'm glad because I have the 15/16 bore for my manual disc conversion on Vixen. Comin soon to a theater near you. lol
Couple of things to consider.
- fluid does not compress.
- smaller diam m/c gives more pressure & therefore less pressure reqd on the pedal [ compared to larger diam m/c ]
- not all m/cs are created equal. Bigger discs often have larger caliper pistons. While the 15/16" m/c might be the 'right' size for pedal feel & pressure, it displaces less volume. The m/c needs enough volume for the job, & bigger pistons need more volume. So volume requirement needs to be checked out.
- fluid does not compress.
- smaller diam m/c gives more pressure & therefore less pressure reqd on the pedal [ compared to larger diam m/c ]
- not all m/cs are created equal. Bigger discs often have larger caliper pistons. While the 15/16" m/c might be the 'right' size for pedal feel & pressure, it displaces less volume. The m/c needs enough volume for the job, & bigger pistons need more volume. So volume requirement needs to be checked out.
The smaller bore master will give you more feel of the brakes and feel of the stopping power on the road. Chances are this is what your used to anyway.
The larger one will require more muscle from the leg and grab harder and quicker.
This is how I understand it to be.
I may also go your route. 11.75 discs.
I have the 9 inch drums on the car now so Willwoods may come instead.
moparmat2000
Well-Known Member
I agree. If your going with 2.75" calipers wouldent a 1&1/32" master give you the same feel as a car that had 2.60" calipers and a 15/16" master cylinder. All things being equal?
Ironracer
Gearhead
I'm running the stock 74 power disks "10"?) The upgrade to the 11.75 may never happen nowadays...
Another vote for 15/16"
Manual front K-H, rear drums. When I first swapped from a single pot on my 66 Barracuda, I put on a 1-1/16". The brakes never felt right. Several years later I put in a 15/16" totally happy with the brakes now.
Manual front K-H, rear drums. When I first swapped from a single pot on my 66 Barracuda, I put on a 1-1/16". The brakes never felt right. Several years later I put in a 15/16" totally happy with the brakes now.
Ironracer
Gearhead
Dig that! I should probably replace all the lines. They're original. You should have seen the original gas line at sending unit I pulled out of that damn thing look like you're staring down in the inside of a cave with stalagmites growing up horizontally out of the walls, in a mountain range. When I did the 66 Sat, I bought a tubing Bender, a double flaring tool (cheap ones) a 20$ roll.coil and bent em up myself. Sort of a pain in the butt it was rewarding I learned a few things like using your tubing cutter versus a mini cut off wheel on a Dremel makes a difference when you go to do your inverted flare. The tubing cutter " work hardens" the tube.. the main thing I learned though, even if you change them one at a time, like I did you, should probably keep bleeding the air out of the system as you go, because once you finally change all those lines, and they're all full of air, even if you gravity bleed the system, strange things happen, especially if the guy who sold you the car had somebody hang the calipers inverted. Took me a lot of research to figure out I had to cut a piece of wood to stick to them and then it pull them off and hang them upside down so the bleeder valve was oriented.blew a few wheel cylinders too..
That's part of why I love this hobby. Learning as we go and figuring out "unique " ways to get things done. Sometimes I'm more creative than others. That's when the neighbors hear unnatural words flowing from the garage., lol.
Ironracer
Gearhead
Yessir!
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