Master cylinder conversion

M

metro1

Senior Member
I am going to change my single cup master cylinder to a dual cup on my '59 Galaxie. I have watched several videos on this procedure and it seems simple enough but my present one has 4 mounting holes and the new one has 2. I suppose I'll have to make an adaptor plate for this. I'm sure others have done this already. Any ideas would be helpful.
 
I did this conversion on my '57 Fairlane many yrs. ago. When you get the old one off, it will be obvious which holes to use. I used a '67-'73 Mustang master cyl. meant for cars w/drum brakes front & rear. - F F
 
No power brakes. All 4 drum. When I bought this car the previous was still occasionally driving it. The rear lines had been replaced but not the front. I noticed there was a slight leak where the right front steel line connected to the rubber line. It was towed to my house. Several weeks later I was going to move it to start work on it. When I pushed down on the brake pedal the line popped open at the leak and the petal went to the floor. A lucky break for all! I bought the copper/nickel line from Federal to go with a 2 cup master cylinder. In my opinion that should make the brakes safer.
 
I found when I converted my 55 the top two holes needed to be filled with a bolt and nut to hold a brace on the inside. Look twice on yours to see if it may be similar.
 
Ole Don said:
I found when I converted my 55 the top two holes needed to be filled with a bolt and nut to hold a brace on the inside. Look twice on yours to see if it may be similar.
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Good point! I can't remember if I had to do that or not on my '57. F F
 
[FONT=&quot]A dual reservoir is safer, in my opinion. I've done the conversion on two of my cars - one non-power drum and one power disc/drum. Keep in mind, though, a single reservoir system is also pretty safe when all of the components are in the condition they should be (which is not too far from new.) I should point out to the OP that the problem he encountered with his brakes doesn't illustrate a deficiency with single reservoir brakes so much as brakes in bad or neglected condition. [/FONT]

[FONT=&quot]Both of my conversions were purchased as systems from professional brake component companies that specified them for my specific vehicles. That would be my suggestion to someone doing the conversion, though some folks seem to figure out which alternate master cylinder to use on their own. On some vehicles, under hood clearances can be a problem, so it's nice to have that figured out by the company selling the MC. I can't remember where I got the drum conversion from, but I bought my disc/drum conversion from a place called ABS in California. They have conversions for all kinds of vehicles. [/FONT]
 
Don't forget to check for proper pedal travel when converting to a dual master cylinder! Otherwise your high dollar setup will not work any better than the the old single master! When you lose pressure on one end or the other on a dual setup, the pedal has to go almost all the way to the floor before there is any braking action. If there is not enough pedal travel or too much play in the linkage, you will not have any brakes. Even a thick aftermarket floor mat can cause total loss of braking when a line fails.
 
Measure how far the rod sticks out of your OG master, use the same measurement with the dual master and you'll be close to a proper adjustment.
 
55blacktie said:
Adapter plate not necessary. You need only two holes. You'll know which two holes to use.
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All four bolts secure the entire clutch and brake bracket to the firewall,after you install the dual master you need to reinstall the other two bolts,look under the dash and you will see why they need to go back in. ;)
 
Make sure you get the correct diameter MC for a non power assist. I believe you will need a 7/8”. I made an aluminum plate and painted it black to mimic the old MC on the firewall.
 
Good point. Stock manual-brakes mc should be 1-inch. Wilwood and Dave (Drop em, Stop 'em) recommended 15/16ths for my 55 Tbird-manual brakes/w Wilwood 4-piston Dynalite calipers in the front/original drums in the rear.
 
I made a plate and painted it black when I installed a Wilwood MC. Just looked more finished.
I’d show a photo but can’t figure out how. Can’t even put a photo for an avatar….comes up error..
 
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