converting manual drum brakes to factory power front disc

[Marks1]

Hi everyone, so I got all the parts from Jeff, (droptop73), and they look great on quick inspection, though I may have one of the rotors turned due to a pretty heavy ridge on it. It's probably fine since Jeff said they worked great, but that's just me. Basically Jeff sent me the entire front assemblies needed to put stock front disc brakes on a car that had drums, spindles, hubs/ rotors, calipers etc. THANK YOU JEFF ! My question is I have manual drums now, so I want to use the fairly new master cylinder and proportioning valve Jeff included in the deal. It was for power front disc brakes (not manual front disc brakes, if that was even an option). Do any of you know what other parts I need besides the booster to complete the job ?? FYI my car in an H code, 351 2V with standard 3 speed manual trans.

 

[Sheriff41]

You'll need the vacuum nipple for your intake manifold and the hose from the manifold to the booster.
Consider changing your brake light switch on the pedal while you're at it.
Make sure the proportioning valve is moving freely so you don't get the constant brake light on the dash. Rebuild it if necessary.
Check to make sure the manual and power assist brake pedals are the same from the pivot to the pushrod; if not, you'll need to source a power brake pedal. (I'm not sure on this one but recall there is a difference.)

 

[Hemikiller]

You'll need a power brake pedal. You can get one for an automatic, as they're often cheaper and easier to find, then trim the pedal down to the same size as your current part.

The pedal hanger assembly can stay in place, but you'll need to drill out the the threads in the weld nuts to allow the booster studs to pass through.

Brake light switch is different. Hot tip - document the orientation and position of the switch and spacers.

Order a set of pre-bent brake lines for the front of the car. NPD carries them.

https://www.npdlink.com/product/bra...%2Bline&top_parent=200001&year=1973&year=1973
That's about it, other than the obvious steps of checking the front end for worn parts while you are there.

 

[boilermaster]

Marks1,
This swap should be done all at the same time, do not attempt to run (manual front disc brakes) with your current (manual drum master cylinder) .
Pretty sure your current master cylinder will have a residual check valve for drums installed in the master cylinders outlet.
A residual check valve needs to be in the master cylinder for the rear brakes (drum) but not for discs.
The check valve would cause your front discs to drag.
I believe the term Ford used back then was called (start up pressure), without start up pressure in a 4 wheel drum system, it would cause a very spongy brake pedal.
Also plan on checking master cylinder to booster clearance, that information can be found on this site.
Inspecting your CLUTCH pedal's support's bushings condition might save you lots of time in the future, consider doing this while you make the swap.

 

[Stanglover]

Well, this could end up with the "snowball effect".
Back when I did a booster add-on, I also went the whole hog and added bearings to the clutch pivot from Mustang Steve (Scott Drake make a set as well). This really smoothed the clutch operation. I went a step further and added oil-lite bronze bushings to replace the plastic bushing in all the linkages. Doable for sure, but a lot of work and totally worth it imo.
As for the booster, here are a couple of pics of the opening after I drilled out the old studs. Of course, I removed the entire hanger bracket. On the brake pedal, Mustang Steve supplied a replacement pin that I welded in 2" down from the manual pin. see pic. I think a pin can be bought that either screws in or has a nut and lock washer on the back.
I went with SSBC 4 piston brakes and actually ran these for years before adding a booster and to be honest, I didn't notice much difference. I do use an adjustable valve for the rear drum brakes, so they are totally separate from the front.
Did Jeff supply disc brake spindles? Maybe I missed that bit.

 

[Marks1]

Marks1,
This swap should be done all at the same time, do not attempt to run (manual front disc brakes) with your current (manual drum master cylinder) .
Pretty sure your current master cylinder will have a residual check valve for drums installed in the master cylinders outlet.
A residual check valve needs to be in the master cylinder for the rear brakes (drum) but not for discs.
The check valve would cause your front discs to drag.
I believe the term Ford used back then was called (start up pressure), without start up pressure in a 4 wheel drum system, it would cause a very spongy brake pedal.
Also plan on checking master cylinder to booster clearance, that information can be found on this site.
Inspecting your CLUTCH pedal's support's bushings condition might save you lots of time in the future, consider doing this while you make the swap.

Thank you for you insight Boilmaster. So I figured you couldn't use the drum brake master cylinder, and since Jeff gave me an almost new master cylinder, I figured I'd use it. The only problem is, Jeff told me it's a "power" master cylinder, and from what I understand, that requires I add a booster to use this master cylinder. I don't know if there was an option to have manual disc brakes. If there was, I would just buy a manual disc brake master cylinder, and stick with manual brakes, because right now, the brakes work very well and don't take a lot of pedal pressure. I don't mind manual brakes, my 65 Corvette doesn't have power brakes, and I find the stopping power to be excellent with low effort.

 

[Marks1]

Well, this could end up with the "snowball effect".
Back when I did a booster add-on, I also went the whole hog and added bearings to the clutch pivot from Mustang Steve (Scott Drake make a set as well). This really smoothed the clutch operation. I went a step further and added oil-lite bronze bushings to replace the plastic bushing in all the linkages. Doable for sure, but a lot of work and totally worth it imo.
As for the booster, here are a couple of pics of the opening after I drilled out the old studs. Of course, I removed the entire hanger bracket. On the brake pedal, Mustang Steve supplied a replacement pin that I welded in 2" down from the manual pin. see pic. I think a pin can be bought that either screws in or has a nut and lock washer on the back.
I went with SSBC 4 piston brakes and actually ran these for years before adding a booster and to be honest, I didn't notice much difference. I do use an adjustable valve for the rear drum brakes, so they are totally separate from the front.
Did Jeff supply disc brake spindles? Maybe I missed that bit.

Well, doesn't it always Stanglover ??!! LOL, seems like every project I do becomes bigger than I originally planned. Yes, Jeff sent the spindles, calipers, rotors, new brake lines, brake pads , and the aforementioned "power" master cylinder. Thank you for all of your help with this,

 

[Marks1]

You'll need a power brake pedal. You can get one for an automatic, as they're often cheaper and easier to find, then trim the pedal down to the same size as your current part.

The pedal hanger assembly can stay in place, but you'll need to drill out the the threads in the weld nuts to allow the booster studs to pass through.

Brake light switch is different. Hot tip - document the orientation and position of the switch and spacers.

Order a set of pre-bent brake lines for the front of the car. NPD carries them.

https://www.npdlink.com/product/bra...%2Bline&top_parent=200001&year=1973&year=1973
That's about it, other than the obvious steps of checking the front end for worn parts while you are there.

Hemi, I sure am glad you live in my area, just in case I ever really need you to help me with this project ! Great info and hot tip here, it really gives me the information I need to get this project right. Was there an option to have front disc brakes, without power brakes?

 

[Marks1]

well I see Mustang Steve offers a manual brake MC for disc brake/ drum combo. I guess I could just sell the MC Jeff sold me.

 

[basstrix]

Something for you to check are the metal brake lines that pass through the fender apron and connect to the flex lines which then connect to the calipers. I did this conversion on a 71 ranchero and had to replace those steel lines on both sides. I *think* the mustang is the same, but I'd have to pull a wheel on the mustang to be certain. Here's a picture of the drivers (left) side for reference.

 

[mrgmhale]

Thank you for you insight Boilmaster. So I figured you couldn't use the drum brake master cylinder, and since Jeff gave me an almost new master cylinder, I figured I'd use it. The only problem is, Jeff told me it's a "power" master cylinder, and from what I understand, that requires I add a booster to use this master cylinder. I don't know if there was an option to have manual disc brakes. If there was, I would just buy a manual disc brake master cylinder, and stick with manual brakes, because right now, the brakes work very well and don't take a lot of pedal pressure. I don't mind manual brakes, my 65 Corvette doesn't have power brakes, and I find the stopping power to be excellent with low effort.

Marks1 beat me to the punch. Kudos Marks1! Pretty much any time I see someone asking or chatting about going from drum to disc brakes I get on the soap box and make it clear that a person absolutely must make certain the Residual Pressure Check Valve (RPCV) for the front brake caliper hydraulic output port that was there for the old brake drum system is removed (for the front brakes only, you want it there for the rear drum brakes still). Better yet, get the proper Master Cylinder designed for use with front disc/rear drum brakes, and verify there is no RPCV is in the front disc fluid outlet, as there is likely at least a Master Cylinder bore diameter difference, and perhaps a reservoir capacity difference as well..

The only thing I think Marks1 and I may end up chatting about is the use of a power booster with a disc brake system. The drum brake in 60s and later (and some earlier) brake systems are "self-actuated," not the same as "self-activated." In short, when the brakes are applied in a drum brake system, the anchor pin where the brake shoes press against at the top of the brake assembly, keeps the secondary lining and show assembly from rotating when the primary shoe and lining assembly are pushed toward the drum via the wheel cylinder having pressure applied. As the primary shoe is pressed out into the drum, the secondary shoe and lining assembly is jammed into the drum, and remains jammed because the anchor pin is immovable. With a disc brake system there is no self-actuation process. The disc braking action depends on hydraulic pressure pressing the brake pads against the rotor, and the tighter the pads are squeezed the greater the braking action (to a limit, of course). There is nothing to self-actualize. So, in order to get the kind of squeezing pressure needed on the disc brake pads to really stop hard, a lot of force needs to be applied. Hence, why I feel it is better to have a brake booster whenever a person has disc brakes.

That said, I did have a car once that had unboosted front disc brakes, from the factory. I think it was my very bare bones 1969 Mach 1, in fact I am pretty sure that was the car with no brake booster and front disc brakes. It worked, but I could tell whenever I drove it that the disc brakes took some significant exertion to really slow the car down as opposed to other 69-70 Mustangs I would drive at times, where they had power disc brakes. I get that the booster is not "necessary," so this is not me saying Marks1 is not correct,. It is just me saying I far prefer a brake booster with disc brakes. It makes things so much nicer.

 

[Hemikiller]

Hemi, I sure am glad you live in my area, just in case I ever really need you to help me with this project ! Great info and hot tip here, it really gives me the information I need to get this project right. Was there an option to have front disc brakes, without power brakes?

Not on a 71-73 Mustang or Cougar. You could swap in a 74 Maverick manual disc master, supposedly that'll do the trick. You might have to run adapters on the ports.

https://www.rockauto.com/en/moreinfo.php?pk=113031&cc=1132210&pt=1836&jsn=2793

 

[mrgmhale]

Not on a 71-73 Mustang or Cougar. You could swap in a 74 Maverick manual disc master, supposedly that'll do the trick. You might have to run adapters on the ports.

https://www.rockauto.com/en/moreinfo.php?pk=113031&cc=1132210&pt=1836&jsn=2793

Not meaning to snag your post in this thread. But... I am certain it was my 1969 Mach 1 that had front disc brakes with no power booster. It would have come that way from the factory as the original owner (I was #2) was my dentist and had not a clue about anything about cars. Great guy, excellent dentist, but not a car guy other than buying nice sports and pony cars. At that, usually with few options. My 69 Mach 1 had a fold down rear seat, front disc brakes, power steering, auto tranny, and an AM radio. Nothing else. Ran nicely, I beefed up the engine and auto tranny something fierce within 2 years of owning it.n With 3.0:1 rear axle ratio it was not snappy off the line, but once it got to about 35 MPH there was stopping that high geared pony...

 

[Marks1]

Marks1 beat me to the punch. Kudos Marks1! Pretty much any time I see someone asking or chatting about going from drum to disc brakes I get on the soap box and make it clear that a person absolutely must make certain the Residual Pressure Check Valve (RPCV) for the front brake caliper hydraulic output port that was there for the old brake drum system is removed (for the front brakes only, you want it there for the rear drum brakes still). Better yet, get the proper Master Cylinder designed for use with front disc/rear drum brakes, and verify there is no RPCV is in the front disc fluid outlet, as there is likely at least a Master Cylinder bore diameter difference, and perhaps a reservoir capacity difference as well..

The only thing I think Marks1 and I may end up chatting about is the use of a power booster with a disc brake system. The drum brake in 60s and later (and some earlier) brake systems are "self-actuated," not the same as "self-activated." In short, when the brakes are applied in a drum brake system, the anchor pin where the brake shoes press against at the top of the brake assembly, keeps the secondary lining and show assembly from rotating when the primary shoe and lining assembly are pushed toward the drum via the wheel cylinder having pressure applied. As the primary shoe is pressed out into the drum, the secondary shoe and lining assembly is jammed into the drum, and remains jammed because the anchor pin is immovable. With a disc brake system there is no self-actuation process. The disc braking action depends on hydraulic pressure pressing the brake pads against the rotor, and the tighter the pads are squeezed the greater the braking action (to a limit, of course). There is nothing to self-actualize. So, in order to get the kind of squeezing pressure needed on the disc brake pads to really stop hard, a lot of force needs to be applied. Hence, why I feel it is better to have a brake booster whenever a person has disc brakes.

That said, I did have a car once that had unboosted front disc brakes, from the factory. I think it was my very bare bones 1969 Mach 1, in fact I am pretty sure that was the car with no brake booster and front disc brakes. It worked, but I could tell whenever I drove it that the disc brakes took some significant exertion to really slow the car down as opposed to other 69-70 Mustangs I would drive at times, where they had power disc brakes. I get that the booster is not "necessary," so this is not me saying Marks1 is not correct,. It is just me saying I far prefer a brake booster with disc brakes. It makes things so much nicer.

Gil, you may have convinced me it is worth all the work to make it a power brake car !!

 

[mrgmhale]

Gil, you may have convinced me it is worth all the work to make it a power brake car !!

IMHO I feel any time a disc brake system is in use it ought to have a power booster. That said, there are so many different kinds of boosters. My further suggestion is that unless you get a full kit with a booster and matching Master Cylinder designed for front disc brakes (Wilwood), you reach out to WCCC to have them help you get the correct equipment. Also, on our 1973 Mach 1, which came with 4 drum brakes originally, the prior owner swapped out the power booster, Master Cylinder, and all the Caliper & Rotor equipment from a wrecked 71-73 Mustang long ago. The brake lights do not come on with a very light braking effort, but they do come on once moderate pressure has been applied. The prior owner told me the brake light switch does not fit in its location quite right. I did some research and found there are two different brake switches for 71-73 Mustangs, one for drum brakes, and one for disc brakes. I went ahead and ordered the correct brake switch for disc brakes, but frankly I have not taken the time to swap the current switch with the new one - just because the brake lights do work, and I am not as limber as I once was re: getting up into the location where the switch is located. I only have a few more short weeks before Winter Hibernation is upon us. Now that I have shared this with you I feel inspired to just get it down this week, while I have little else to do. So, many thanks for the inspiration! heh heh...

Here is a link from WCCC I think you find useful:




The folks at WCCC really are top notch.

 

[Marks1]

IMHO I feel any time a disc brake system is in use it ought to have a power booster. That said, there are so many different kinds of boosters. My further suggestion is that unless you get a full kit with a booster and matching Master Cylinder designed for front disc brakes (Wilwood), you reach out to WCCC to have them help you get the correct equipment. Also, on our 1973 Mach 1, which came with 4 drum brakes originally, the prior owner swapped out the power booster, Master Cylinder, and all the Caliper & Rotor equipment from a wrecked 71-73 Mustang long ago. The brake lights do not come on with a very light braking effort, but they do come on once moderate pressure has been applied. The prior owner told me the brake light switch does not fit in its location quite right. I did some research and found there are two different brake switches for 71-73 Mustangs, one for drum brakes, and one for disc brakes. I went ahead and ordered the correct brake switch for disc brakes, but frankly I have not taken the time to swap the current switch with the new one - just because the brake lights do work, and I am not as limber as I once was re: getting up into the location where the switch is located. I only have a few more short weeks before Winter Hibernation is upon us. Now that I have shared this with you I feel inspired to just get it down this week, while I have little else to do. So, many thanks for the inspiration! heh heh...

Here is a link from WCCC I think you find useful:




The folks at WCCC really are top notch.

Gil,
I received an almost new, original style Power Master Cylinder in the package I bought from Jeff, (DropTop73) I think I'd like to stay as original as possible, since this is a factory disk brake setup, spindles, rotors, pads, calipers, hoses, Power Master Cylinder, etc. So I'd like to stay with a factory pedal, booster etc. Our car is almost completely original, other than the paint, so we've decided we are going to try to go survivor with it.

 

[turtle5353]

I have run the manual drum brake master cylinder for years with my disc brake setup. I have discs brakes all the way around and still have the original manual master cylinder.

 

[71coop]

Not on a 71-73 Mustang or Cougar. You could swap in a 74 Maverick manual disc master, supposedly that'll do the trick. You might have to run adapters on the ports.

https://www.rockauto.com/en/moreinfo.php?pk=113031&cc=1132210&pt=1836&jsn=2793

That will do the trick (I did it) but you still need to add a couple things. You need the Maverick MC, its well suited for this application. I bent my own lines between the MC and the stock distribution block. I had to add a residual valve and an adjustable proportioning valve in line with the rear brake lines, just in front of the rear end, where the floor pans curve up to make room for the rear axle assembly. Those were very easy to plumb under the car vs in the engine bay. Way less work that going full power, and in my experince, works really well.

 

[AcesArneson]

Mustang Steve sells a conversion kit if you're interested. I bought one but have not installed it yet. You'll need minimum 18" wheels to fit the 2015-2019 GT brakes on your 65-73
https://mustangsteve.com/product/s550-brakes-on-65-73-mustang/

 

[Marks1]

That will do the trick (I did it) but you still need to add a couple things. You need the Maverick MC, its well suited for this application. I bent my own lines between the MC and the stock distribution block. I had to add a residual valve and an adjustable proportioning valve in line with the rear brake lines, just in front of the rear end, where the floor pans curve up to make room for the rear axle assembly. Those were very easy to plumb under the car vs in the engine bay. Way less work that going full power, and in my experince, works really well.

Awesome to here of someone who actually experienced this conversion, Thank you Hemi and 71 Coops !! Out of curiosity, How do you find the pedal effort? I'm being told it's really high, but I don't find my manual four disc brakes on my 65 Vette Coupe to be high.