Dual Master Cylinder

rafter

rafter

Member
I want to up-grade to a dual master cylinder on my Model A hydrolic brake system. I'm wondering if a 78' Ford F250 PU master will work. It's a dual cylinder with a bore of 1 1/16". Any reason why it shouldn't work? Is there something better I should be looking at? Thanks, Rafter
 
I think the Early Ford v8 guy has problems with installing dual master cylinders on old Fords. I can not remember his name but he is an expert and sells kits for conversions. I hope he sees your post. Everybody seems to respect his opinion and he is a nice person.
 
l build battery boxes with a duel stage master cly. use early mustang cly. you can get these drum drum or disc drum(for hotrod guys)
 
rafter said:
I want to up-grade to a dual master cylinder on my Model A hydrolic brake system. I'm wondering if a 78' Ford F250 PU master will work. It's a dual cylinder with a bore of 1 1/16". Any reason why it shouldn't work? Is there something better I should be looking at? Thanks, Rafter
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A tab bit more info may help answer your question more accurately, like what kind of brakes you have, as Model As had mechanical brakes. If they are '39-'48 Ford brakes, the '78 F-250 master should work fine, as it has the same bore as the early Ford master. If it's disc/drum, all the better, as the front brake (larger) chamber is obvious. Just use a new/rebuilt master, not an original one taken from a '78 F-250! :)
 
With Ford juice brakes 39-48 style a 68 Mustang Master Cylinder works very good. Get the non power version and you won't need extra proportioning valves. There is an easy way to leave all the model A pedal set-up in there as well.

You need to find or make another lever like the current manual rod attaches to. If you take and bolt the new m/c to the passenger side of the square cross member where there is already a hole for a RHD brake rod towards the front side of the car and attach the new lever and make a brake rod you are done. Minor filing of the existing hole through the cross member may be needed. Plumb and drive.


Good Luck,

Tim
 
rafter said:
I want to up-grade to a dual master cylinder on my Model A hydrolic brake system. I'm wondering if a 78' Ford F250 PU master will work. It's a dual cylinder with a bore of 1 1/16". Any reason why it shouldn't work? Is there something better I should be looking at? Thanks, Rafter
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I would check two more things. What is the pedal ratio of the truck and what is the diameter of the truck wheel cylinders. Sure sounds like you may be onto something.

Charlie Stephens
 
I would check with early V8 Ford guy before I did anything. He has been in the business a long time. I can not remember why he does not like dual master cylinders. I could be all wrong to about this subject.
 
rafter>>>I want to up-grade to a dual master cylinder on my Model A hydrolic brake system.>>>

Good idea! Also good idea to get a new or rebuilt rather than a "used" as suggested above. If you've got 4 drums, just about any dual will work when properly plumbed.

Jack E/NJ
 
sturgis 39 said:
I think the Early Ford v8 guy has problems with installing dual master cylinders on old Fords. I can not remember his name but he is an expert and sells kits for conversions. I hope he sees your post. Everybody seems to respect his opinion and he is a nice person.
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I have posted in the past some of the issues with so-called "dual" master cylinders. This is one of those subjects that people do not agree on. Depending on how your MC and pedals are set up, the 1-1/16" bore is the same as what was originally used with Ford and Lincoln-Bendix brakes, as well as F-1 and F-100 Bendix brakes. The issues are that the pedal ratio must be compatible so that FULL MC piston STROKE is achieved and the brake shoe clearance must be kept at a minimum so that stroke is not "wasted" by excessive clearance. Otherwise, if the dual MC does not have built-in residual valves for drum brakes (usually 10 lbs) they need to be added in each line as near to the MC as possible. The reason these things are important is that the so-called "dual MC's" are not two independent circuits, but are co-dependent on pressure being present in each end to operate under normal conditions. If pressure is lost in either end, the MC piston must travel much more to recover brakes in the surviving end. Without sufficient pushrod travel, this cannot happen and there will be no brakes. Ford pedals are limited by the length of the pedal stems and by how much travel can occur before the pedal hits the floor/mat/carpet or whatever.

Proper bleeding procedure must be followed in order to remove all air from the system, and due to the design of the "dual" MC's, it is not as simple as bleeding a single MC.

I would encourage anyone/everyone to read a Motors Manual or comparable technical book that explains exactly how these dual MC's operate (they are actually "tandem" and NOT two independent systems...) so you can have realistic expectations regarding what will happen should a system failure occur. Done right, they are fine, but you still need a good handbrake backup.

Another issue is availability of space as compared to a single MC and access through the floor. "Dual" MC's typically require a much larger hole in the floor AND due to typically taller reservoirs and/or cover, installing one without major butchery can be a challenge.

I wrote this in about 5 minutes, so this is NOT a comprehensive, all bases covered post.
 
Thanks Richard. Could you provide a sketch? I have waited a long time for you to reply.
You must have been on vacation.

I guess I do not understand the term tandem. Does one piston push brake fluid into the other piston?

Thanks again
 
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I used one of a reg cab 70's Ford truck disk /drum it has porp valve in it already but I did put disk up front.Had no trouble mounting on frame.
 
Richard (EV8G)>>>If pressure is lost in either end, the MC piston must travel much more to recover brakes in the surviving end. Without sufficient pushrod travel, this cannot happen and there will be no brakes.>>>

Sadly, this situation exists even for some modern factory-installed duals. I had a 1993 wagon that popped a rear line while slowing for a red traffic light at the bottom of a hill. Pedal to the floor and no front brakes either. Handbrake wasn't enough to stop the wagon from running the red light. Luckily no other car was going thru the intersection green light as I sailed thru. Poor design engineering.

Jack E/NJ
 
Jack E/NJ said:
Richard (EV8G)>>>If pressure is lost in either end, the MC piston must travel much more to recover brakes in the surviving end. Without sufficient pushrod travel, this cannot happen and there will be no brakes.>>>

Sadly, this situation exists even for some modern factory-installed duals. I had a 1993 wagon that popped a rear line while slowing for a red traffic light at the bottom of a hill. Pedal to the floor and no front brakes either. Handbrake wasn't enough to stop the wagon from running the red light. Luckily no other car was going thru the intersection green light as I sailed thru. Poor design engineering.

Jack E/NJ
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This situation would only happen IF there were other serious problems or failures with the brake system. Yes, the pedal will travel farther when one system fails, but should not go to the floor. That's fact, not opinion, based on FMVSS 105/135 brake system compliance that vehicles must meet using hydraulic brakes since 1967.

In your case, worn out pads and/or rotors, loose wheel bearings that allow too much caliper piston retraction, an internal problem (leak) with the master, etc, could have caused the total pedal loss. With a displacement issue, an extra pedal pump usually will bring that system back to working order. If the brakes are all in good working order, a hydraulic failure will allow FULL braking in the remaining system, although with longer pedal travel. :)
 
Possibly Bob. But at the time, the only issue found by a Meineke shop was the ruptured line due to corrosion at a line hanger, granted they may not have carefully checked everything else out. As for the extra pedal pump, 3 or 4 frantic attempts were made before going to the handbrake equally frantically. After stopping and trying to compose myself, several more pumps did bring some pedal back --- enough along with the handbrake to feel safe and composed enough to limp along to the shop.

Jack E/NJ
 
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