Master cylinder conversion
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Cross-Country
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Master cylinder conversion
I'm converting the original master cylinder on my '53 F100 to a late 60's Mustang dual reservoir drum/drum type using an adapter bracket. I'm keeping the original drums for now, so not using a proportioning valve. This seems to be a popular conversion, so I'm hoping members can answer a question. Which port on the master cylinder goes to which pair of brakes, or does it matter? Thanks for sharing your experience --
Parts Nerd Extraordinaire
Joined: Sep 2010
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From: Western NY
That era mustang had a few different master cylinder setups with various permutations of powered/manual and disc/drum... it would probably help to know which exact master cylinder you are going with.
Laughing Gas
Joined: Mar 2002
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From: Newton Illinois
I do not think that it will matter but I would use the side with the larger reservoir for the front, if you switch to front disk you will then be set, make sure and use 10PSI residual pressure valves on both sides.
One problem with not running a proportioning valve at all is that if you loose a brake line you will lose brakes to all 4 wheels despite the dual master cylinder.
One problem with not running a proportioning valve at all is that if you loose a brake line you will lose brakes to all 4 wheels despite the dual master cylinder.
Hotshot
Joined: Oct 2009
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From: Burbank, WA
Originally the rear reservoir, or the one closest to the firewall and pedal, was for front brakes, and vice-versa. If you're mounting it in the stock location under the floor, you'll be turned around backwards, so the one closest to the pedal will now be forward and should go to the front brakes. Does that make sense?
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I do not think that it will matter but I would use the side with the larger reservoir for the front, if you switch to front disk you will then be set, make sure and use 10PSI residual pressure valves on both sides.
One problem with not running a proportioning valve at all is that if you loose a brake line you will lose brakes to all 4 wheels despite the dual master cylinder.
One problem with not running a proportioning valve at all is that if you loose a brake line you will lose brakes to all 4 wheels despite the dual master cylinder.
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Laughing Gas
Joined: Mar 2002
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From: Newton Illinois
Thanks. Since it's a master cylinder for an all drum system, both reservoirs are the same size. I'm confused over the need for a proportioning valve. The stock Mustang 4 wheel drum system didn't use one. It did have a differential pressure valve that grounded the brake warning light circuit if there was a failure. I was under the impression that the front and rear were isolated from each other within the master cylinder, but I'll look into that.
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Phantom of the Phorum
Joined: Jan 2011
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From: Kentucky
Originally the rear reservoir, or the one closest to the firewall and pedal, was for front brakes, and vice-versa. If you're mounting it in the stock location under the floor, you'll be turned around backwards, so the one closest to the pedal will now be forward and should go to the front brakes. Does that make sense?
My MC is for a 1968 Mustang, 4-wheel drum, no booster. Duralast #NM1485. My understanding is they have residual-valves built-in from the factory.
It actually fits a slew of Fords:
Mustangs:
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I found this video to be helpful in understanding how the master cylinder effectively isolates one chamber from the other when either one fails. The isolation takes place by closing compensating ports in the master cylinder and is independent of proportioning or pressure differential valves in the system. I think I would want the primary piston, which builds pressure first to activate the brake light switch and go to the front wheels
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