OK,,,I am back to the best source anywhere for good advice again. I have a 58 Ford Courier, stock rear drum brakes, discs in front from a 68 big block LTD. I had a brake booster/master cylinder combo on it years ago that was from a Ford Fairmont. It would stop on a dime, but the pedal went almost to the floor. No adjusting/bleeding/etc. would cure it because I learned the pedal pivot ratio was wrong for power brakes. I tried to help it by putting a bigger bore master cylinder on it,,,more fluid with less travel. I am quite sure it is a 1 1/16" bore. That helped some, but there was still a lot of pedal travel. Took the automatic out later and put in a 5 speed and the clutch linkage hit the brake booster, so I took that off and kept the same master cylinder. It stops fine with a good pedal but it pushes hard. Stops fine, but it takes a good leg. I checked a master cylinder for a mid 70s Ford with manual/disc/drum brakes and that shows a 1" bore. Will that 1/16" smaller bore help. I would like to go a little smaller, but haven't found a cylinder with smaller bores yet. Any suggestions? Help appreciated as always.
I use a 7/8” MC bore and 15/16” rear wheel cylinders with a stock 56 pedal assembly wheels is near 5-1. It’s almost like power and better than when the car was all drum. I have plenty of pedal. I also use Wilwood 4 piston calipers which may may a difference. There are many different diameter caliper internals which may be part of the problem. Good luck.
I have a 1" bore master in my '59 Ford and it works quite well. How about a '68 LTD master? Although I believe it puts the lines on the inside towards the engine. My master is speced out for a '72-ish disc/drum Mustang.
Speedway motors in Nebraska has an excellent article about master cylinder and wheel cylinder and caliper size. Go read it.
@birdman1, hope this is the correct article about master cylinder sizing: https://www.speedwaymotors.com/the-toolbox/changing-bore-size-on-a-master-cylinder/30895 Phil
I have looked up 68 LTD cylinders and they are 1" bore also, but they don't show 68 with manual front discs, only power. And with them, 1 port comes out the side, the other out the bottom with a bleeder on the side where the 2nd port would normally be. I would prefer not to have to make new lines if I could. I put this 1 1/16" cylinder on it long, long ago and somewhat forget, but I think it is a Chevy, maybe Corvette cylinder. The ports are on the engine side. I can buy a 73 Torino 1" cylinder for under $30, so I might try that. I called a brake place and they said just dropping from 1 1/16 to 1 would help some. Thanks for your help!
Check out Wilwood's site. lots of good info there. I use a 15/16" Wilwood on my manual brake system, o/t grocery getter & it works great. The smaller the MC bore the more mechanical advantage you will have. Your 58 is gonna be heavier than my o/t Falcon, so do the research. Brakes are too important to just "wing it".
Ok, I have found a Ford Fairmont Mc with 7/8 bore. Not sure if that might be too small. Need to decide between that one or the 1 inch Torino one. Both are inexpensive, so might try the 1 inch. Any input?
The Fairmont was a pisspot of a car compared to a Galaxie. I always try to get the donor master as close to the size of the car it will be going into. My master I got at Speedway for around $43 at the time and it is speced out against a Fairlane or Mustang, also light cars but in my case stops the car well.
My opinion would be try the one inch. That's what I use on my chevelle, which has disc in front and drums in back (manual)
Power 1" or larger. Manual 15/16" or smaller. If I could change my pedal ratio from 5-1 to 6-1 it would be like adding a vacuum booster.
this truck has a 7/8 bore dual master in it, gm calipers up front stock 11" drums in the rear. pedal is very responsive, best brakes on an old truck you could ever have. I can outstop my wifes DD mini cooper with it. larger bore masters run less pressure, more volume, and that leads to softer pedal feel, using more mechanical pressure to create pressure, hence why power boosted cars have large dia bore. booster does the work of your leg. Residual valves help caliper take-up room, and same with drums needing a bit of residual presssure to make short take up in the slack. The proportioning valves most people run are very unsuited for a good brake system, most are meant for power systems not manual anyways. My 53 bel air has a proportiong block and I hate it, the 56 pickup has a wilwood adjustable proportioning valve in the rear brake lines to control bias, front and rear lines have residual valves, The truck stops like a sports car, everyone who has driven it has praised the brakes and are astounded by how well they work.
Going from a 1.0625" (1 1/16) bore to a 1" bore will require 11.5% less input force to create the same output pressure. The downside is that it will also require a corresponding increase in pedal travel to move the same volume.
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