Juice brake question

37 Cab

37 Cab

Well-known member
I know this is a long shot but here goes. My 37 had a brake conversion don't by previous owner. Brakes have never been very good. It has 40 backing plates with top and bottom adjusters. I have adjusted them twice and blead them twice. (no air) Still, the pedal is low. I now suspect the master cylinder is either bad or too small. It is a dual reservoir type with the lines coming from the outboard side with the cylinder pointed to the rear.
My question is, Can anyone recommend a master cylinder with a large enough bore to support the 40 brakes? I am not sure but the one I have may be mustang?? Only because I have heard that was a common one to use. Don`t know the bore size without removing it but I think mustang used a 7/8 bore??
I am looking to fix this problem once and for all this winter so a rework is not out of the question. Any and all advice is much appreciated and some pictures or part numbers would be very helpful. Also.. I believe the pedal assembly is still a 37.
 
You really need to measure the bore on the master you have. Early Mustangs were all 1", Mustang 11s were 15/16" and some late '80s/early '90s were 7/8".
The "39-'48 Lockheed masters had a 1 1/16" bore, but a 1" works fine in many dual conversions using the Lockheed drums.
 
The Lockheed brakes are somewhat difficult to adjust, are you sure you are doing it properly?
 
I had a similar situation with my 35. My dad made the conversion 50 years ago or so and I'm assuming they worked well for him all that time. After I restored the car...including master and brake cylinders...the pedal was always fairly low and sometimes I'd have to give it a couple pumps. I bleed the system a couple times and no change. When I broke an axle last year, I replaced the back brakes and adjusted them correctly (this time). I noticed the pedal was higher than it has been. I decided to adjust the front brakes correctly (this time) and now I've got a ton of pedal...it's perfect. Moral of the story is that, in my case, incorrectly adjusted brakes caused a low pedal.
 
This is the procedure I followed. Made no difference.

Step 1: Loosen the anchor pin large lock nuts (usually 3/4") on both shoes of one wheel just barley enough to permit turning the 1/4" anchor pin adjusters. Now, turn both of the 1/4" adjusters so the locator marks face directly towards each other. This next point is important .... All further adjustments are made by turning the anchor pins (1/4") and eccentric (11/16") downwards.
Step 2: Back off the upper eccentric cam adjusters on both shoes until the wheel rotates freely.
Step 3: Now turn one of the upper eccentric (11/16") until the wheel cannot be turned.
Step 4: Now turn it's 1/4" anchor pin adjuster downward until the wheel just turns freely. This lowers the shoe and moves the toe of the shoe away from the drum and results in fuller shoe contact.
Step 5: Now go back to Step 3 and do it and step 4 again to the same shoe. Repeat as necessary until turning the 1/4" anchor pin adjuster will no longer free up the wheel. Back off both anchor pin adjuster and upper eccentric just enough so the wheel has a slight drag. Tighten the anchor pin lock nut (3/4") without letting the anchor pin adjuster move. Now do the other shoe the same way.
 
Mid 70s E250 had a dual circuit 1-1/16" master cylinder. I used one to replace the 1" Mustang cylinder on my roadster. Be warned, though, it is quite a lot bigger than the relatively compact mustang cylinder. I'm not sure if the bolt spacing for the mount is the same. (I made new mounts for another reason).

In checked 1977 Ford E250 at rockauto and that is the one I used.

Mart.
 
Just an observation : I've been watching these forums for a number of years and just about every time I see a thread about "unsatisfactory" brake pedal, the master cylinder has been "updated". I'm starting to wonder if bore size, stroke and other factors aren't more important than we have thought. There was a thread here a couple of weeks ago from a guy who was very dissatisfied with the brand new brake system in his '51 Ford with a new dual master cylinder. I have a '51 Ford that I replaced everything on as well, except that I kept the stock master cylinder. I can lock up all four wheels anytime I want. (I might not be able to do it 3 or 4 times in a row, but I can not see how a situation like that could ever arise; I'd be too busy cleaning my pants from the first time.)
 
tubman said:
Just an observation : I've been watching these forums for a number of years and just about every time I see a thread about "unsatisfactory" brake pedal, the master cylinder has been "updated". I'm starting to wonder if bore size, stroke and other factors aren't more important than we have thought. There was a thread here a couple of weeks ago from a guy who was very dissatisfied with the brand new brake system in his '51 Ford with a new dual master cylinder. I have a '51 Ford that I replaced everything on as well, except that I kept the stock master cylinder. I can lock up all four wheels anytime I want. (I might not be able to do it 3 or 4 times in a row, but I can not see how a situation like that could ever arise; I'd be too busy cleaning my pants from the first time.)
Click to expand...

Main problem in many cases is not fully understanding the brake system, correct bleeding procedure, and the importance of pedal return springs and proper clearance of the push rod(s).
The addition of a dual master is an important safety upgrade, not performance, as the brakes will operate exactly the same, good or bad.
JFYI, I'm running a Mustang dual master in my stock-braked '51 with no issues. :)
 
I'm not saying it is a bad thing, just that one should be careful when selecting parts and setting up the system. I think we're on the same page here except I think having a proper single master may be better than having an unsuitable dual unit.
 
You may be right. For sure bore size and stroke are important. I put the car on the lift today and after looking the pedals are not 37. I was thinking of the lever at the park brake where the cables used to attach. The pedals and bracket appear to have been designed for a 3 bolt master cylinder. This is my first old Ford so I don`t know what they are from. 39?
I was trying to describe the master cylinder in hopes someone could suggest what it came from. Did some looking there too. The pushrod is attached under the snap ring via washer so the rod comes off with the master cyl. and is then removed. The kind used on some cars on cars without power brakes. I didn`t take it all the way off but was able to get my caliper onto the bore outside the snap ring. It measured just over .900 so no way this is a 1" master. Probably 7/8". I would like to stay with the more compact master and go to a 1" bore with the lines coming out the same side as they are now. Does anyone recognize the one I have? Not sure which side the mustang unit brake lines are on. ?? If I order a mid 60s Mustang master are drum and disc brake cylinders the same?
Here are some pictures I took. need help identifying just what I have. Everything I look at seems to have the lines on the opposite side. I can redo the lines but would like to avoid if if I can.
Thanks guys. I appreciate your help.

IMG_1943.jpg

IMG_1946.jpg

IMG_1947.jpg

IMG_1949.jpg

IMG_1950.jpg

IMG_1951.jpg
 
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I think someone mentioned some American motors masters had left side outlets.

found it

Should be 10-1373 or 101373 '70 Gremlin 1" bore left outlets; double check this info, of course.
 
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Perfect Rich. Never would have thought to look at American Motors. Found this one for a 68-74 Javelin with a 1 1/16" bore.
RAYBESTOS MC36456

Thank you!! Are my pedals a 39 set up?
 
Bitchen cabriolet and Rare ! I know this has been a issue I have seen on a number of cars with low pedal and poor braking is the drum diameter . Did you check to see if the drums have been turned to much? Over 12 .062?
 
37 Cab said:
...
My question is, Can anyone recommend a master cylinder with a large enough bore to support the 40 brakes? ...
Click to expand...

I am planning to upgrade from single to dual cylinder master but am putting it off until I feel comfortable flaring and bending 3/16" tubing...which is necessarily a part of the conversion.

I will use Wilwood masters, probably 1" bore, but 7/8" and 1 1/8 are available. They are expensive but have a greater workmanship quality over castings plus the advantage of remote reservoirs. Outlets are either side.

Have you considered using 10psi residual pressure valves which are necessary for drum brakes front and rear, and not always built into the master cylinder? Residual valves will provide a higher pedal as wheel cylinders will be held out slightly rather than retracting completely.
 
vulture said:
Bitchen cabriolet and Rare ! I know this has been a issue I have seen on a number of cars with low pedal and poor braking is the drum diameter . Did you check to see if the drums have been turned to much? Over 12 .062?
Click to expand...

Have not checked the drums yet but since I now know the master cyl is too small I will do that next. Wouldn`t arching the shoes... Nevermind. Don`t know that has been done either. Some of the work done to my car before I got it makes me think I saved it rather than acquired it. Got it mostly sorted now but it has been a journey. Almost like they put it together just to look at it. Don`t know when it was done as I didn`t get any history on the car but it has been together for a long time.
 
When you consider that hydraulic brakes use an in-compressible fluid to deliver the force of the driver's foot to a master cylinder which delivers a fixed amount of fluid to 4 brake cylinders, I find it amazing that is is possible to take a bunch of parts from 40 years and 8 manufacturers to produce a system that is sort of equivalent to what Henry put out with rods and/or cables.

IMHO

Not that I would drive at 70 with Henry's brakes!
 
You have a few issues.

The master cylinder is too small.
It is on a very poorly designed home made adaptor bracket.

If it were my car:

I'd throw away the dual master. I would buy a decent new early ford type master cylinder. I'd buy all the standard Ford banjos and fittings to run the pipes in 1/4" like stock 39.

The belief that changing to a dual master will give a safety benefit may be ill founded. This has been discussed before on this forum. If one side fails, you will probably not have enough extra pedal travel available to get the remaining brakes on effectively.

I bought a very presentable Early Ford type single master cylinder from Rockauto for my 41pu recently. It looks well made even though imported.

If you decide to go with a dual:

Get a 1" or 1-1/16" master.
Get a commercially available adaptor to bolt it to the pedal box. Or:
Make a 3rd standoff to brace the adaptor plate to the lower bolt hole in the pedal box.

It would be interesting to get under your car to see what happens if the pedal is pressed hard by an assistant. I think you would be surprised by the amount of flex in that bracket. Supporting on two bolts not in line with the line of force is a big no-no.

I'd strongly advise getting a stock single circuit master and running that.

The car is well looked after, a lift is available, pipework and fittings can be inspected and maintained.

The dual master is fitted by manufacturers knowing that no-one will look at it for the next 10, 15 or 20 years. When you take that neglect factor out of the equation, a single master, especially one following original factory design is (in my opinion) the best bet.

Mart.
 
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