Newer ford dual mastercylinder on 40 ford brakes

[HemiDeuce]

Originally Posted by HemiDeuce

I drove my Roadster with the new Master Cylinder today and I worked great.
The pedal was nice and high and the extra 1/16" on the bore of the Master Cylinder made a nice difference in the stopping power.
I very happy how it worked out.
HemiDeuce.

Just a quick update on the Wilwood Master Cylinder that I reported on in the previous post.
After driving my 32 Roadster to the LA Roadster Show I discovered that the rear brakes were not receiving very much pressure from this new master cylinder. Whether it is designed this way, or the master cylinder defective I'm not sure. I replaced this master cylinder with a 1" bore 1967 Mustang dual bore cylinder and the brakes work much better.
The search continues for a 1 1/16" bore dual master that we can use with our early Ford and Lincoln brakes.
HemiDeuce.

[Gary in Mozarks]

Originally Posted by FRANK PKNY

I can tell you from expierence that a single master cylinder set up should never be used. I lost my brakes years ago in a dump truck and went straight through a intersection off the road and into a building. Luck had me and I survived and no one got hurt. Ever since then I have always converted my brakes to a dual system. Better to be on the safe side. Frankpkny

Frank,

I had a simular situation many years ago. A friend of mine was showing off, (burning rubber big time) in a 500 hp 55 chevy with a single master cylinder. I watched in horror as he proceeded to plow into the back of a UPS truck because a brake line ruptured over his rear differential. I ALWAYS convert.

[Gary in Mozarks]

Here is a picture of my 39 ford dual master cylinder installed using a ECI adapter kit. I ran the brake light switch off the rear line.

[19ED30]

Bump ,,, this is a interesting thread , I am looking at a 1 1/4 bore for my 32 ford with 40 brakes , anyone use a Dual master cylinder this big ???

[JSeery]

Originally Posted by 19ED30

Bump ,,, this is a interesting thread , I am looking at a 1 1/4 bore for my 32 ford with 40 brakes , anyone use a Dual master cylinder this big ???

Is there any reason you are wanting to use a large bore master cylinder? It reduces the brake stroke required, but it also reduces the brake pressure to the wheel cylinders. The larger the diameter of the mater cylinder bore the lower the braking pressure.

As an example of line pressure:

line pressure = leg pressure on pedal x pedal ratio divided by cross-section area of master cylinder.

Just for an example, us 150 lbs of leg pressure and a 7:1 pedal ratio.

for a 1 inch bore cylinder - (150 x 7) / .7854 = 1337 psi line pressure

for a 1 1/8 in bore cylinder - (150 x 7) / .9940 = 1056 psi line pressure

for a 1 1.4 in bore cylinder - (150 x 7 ) / 1.2272 = 856 psi line pressure

[42merc]

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Most of the theory has been thrashed before.
The reason we're going to the larger bore M/C is because of the limitations associated with the existing '39-'48 Ford limited pedal ratios & travel.
Small bore = more pedal travel, you don't have enough travel with stock old Ford pedal setups.

[JSeery]

Everything with brakes is a balancing act, pedal travel, pedal ratio, bore size, etc. It all works as a system and each component needs to be correct for the combination to work correctly. Still 1 1/4 is a large master cylinder bore size, I would think that through before typing it.

[V8COOPMAN]

In other words, it may take pushin' with both feet to get things slowed-down. DD

[deuce lover]

Originally Posted by 42merc

Most of the theory has been thrashed before.
The reason we're going to the larger bore M/C is because of the limitations associated with the existing '39-'48 Ford limited pedal ratios & travel.
Small bore = more pedal travel, you don't have enough travel with stock old Ford pedal setups.

Last sentence IMO is not true.Last 4 cars I built I used a 7/8" bore dual MC and worked perfectly.That MC work fine with disc/disc,disc/drum and drum/drum.In each case I used the 39 Ford pedal assy w/adapter to the dual MC.

[40cpe]

Originally Posted by deuce lover

Last 4 cars I built I used a 7/8" bore dual MC and worked perfectly.That MC work fine with disc/disc,disc/drum and drum/drum.In each case I used the 39 Ford pedal assy w/adapter to the dual MC.

Would you please share the application or part number for that master cylinder? Thanks, Gene

[19ED30]

The way I was reading this thread was, on early Ford's had a 1 1/16 bore mc, ( single reservoir ) Front w/c 1 1/4 , rear w/c 1 1/8 . If you where to convert to a dual Mc & if you use a Biger bore ,would be less peddle movement & more brake pressure to wheel cylinder ( a little help like a power brakes )
I check my car out every 2,000 miles change oil ,service every thing , on lift,
When I was 16 I was street Racing my X race car ,late @ night ,quite fast at the time & lost brake , It had a single M/c reservoir , If I would have been @ the drag strip , I would have not been able to stop ,with out a crash , I did use the old under dash hand brake to stop ,
Even to this day ,I even run dual hand brakes in my Blown Altered,(no front brakes ) 4 calipers on the rear,
1 hand brake for each set , parachute's just slows you down .
My 32 has its Original steel , I drive daily 300-500 miles a week , Pepole always pulling out in front of you , Off topic, but does any one remember rule of thumb,
For every 10 mph ,you put 1 Second between you and the car you're following ,So if you're running 70 it should be seven seconds !!! Does this rule apply anymore ,,
because everybody is up my A$$!!
I do not like to driving aggressive, I'm not saying I'm the best driver but I'm sure there's not too many around me that can drive like I can !!
Not quite 50 yet

[V8COOPMAN]

The "TWO SECOND" rule applies and works well, no matter the speed. SOME folks may need to think this out to finally realize that it works. "THREE second" rule applies in rainy conditions. DD

[42merc]

Originally Posted by deuce lover

Last sentence IMO is not true.Last 4 cars I built I used a 7/8" bore dual MC and worked perfectly.That MC work fine with disc/disc,disc/drum and drum/drum.In each case I used the 39 Ford pedal assy w/adapter to the dual MC.

In my applcation it is true.

Had F100 drum all around on my '40, yes all around, 15/16" M/C worked well.
Went to a front disc kit on the front, could get only 1/3 pedal with the 15/16" M/C. Changed to a 1" M/C, now have a good 2/3 pedal.

I do not want to go to a larger bore because of the effort required.

This is what works for me.

[19ED30]

42 Merc, yr quote

I do not want to go to a larger bore because of the effort required.

You are using Disc & drum ?
On my 32 , 40 drums on all four , & you are saying the Biger bore Mc will required More effort from my leg (pushing power )
I would think Less because of more Volume,
Is this not correct?

[FlatheadTed]

Something to be aware of is some 40 wheel cylinders are not drilled correctly at the inlet port and bleed hole ,they have a 1/4 " hole instead of a 1/16 and the cup straddles it specially when fully adjusted backed of , As I understand it the GM two reservoir master cylinder is the one to use 1 n1/16 or 1-1/8,don't know the part number .I worked on a 32 Roadster the car could not be pushed around due to the disc brakes being on slightly heating the brakes up .This had the residual valve that could be moved from port to port so we moved it to the back problem solved , Another part that's not well under stood is what type of lining should be used on a given brake system rods verses hydraulics ,a 40 brake system often power boosted linings are used and result in poor braking .If you have rods try and get them working if they are driven under 60MPH .The rust in cylinders on cars that are not driven frequently is a problem .Ted


Qaute I run singles on my own cars... but this is one of those on-going controversial subjects... (DOT 3 vs. DOT 5, mechanical vs. hydraulic, etc.) I can furnish my 1932 and 33-34 conversions with either type, but 35-36's and 37-38's are limited by space constraints... which is also an issue when a 39-later is converted to a
dual MC.

[JSeery]

Originally Posted by 19ED30

42 Merc, yr quote

I do not want to go to a larger bore because of the effort required.

You are using Disc & drum ?
On my 32 , 40 drums on all four , & you are saying the Biger bore Mc will required More effort from my leg (pushing power )
I would think Less because of more Volume,
Is this not correct?

Did you read my post #45? No, Bigger bore means more leg pressure, smaller bore less leg pressure. Not sure why so many seem to have this backward. The larger the bore in the master cylinder the lower the line pressure and the more leg force that is required. The only reason to go to a larger master cylinder diameter is if you are having brake pedal stroke problems. The larger cylinder diameter will move more volume of fluid (at a lower line pressure) and require less pedal travel. You really need to understand how all of this works together, the system has to be matched, you can't put just any master cylinder with any pedal ratio, they work together.

This is not one of the subjects that is just an opinion, it is the facts of physics. It doesn't matter if it's an engine hoist, floor jack and car brakes, this is how fluid physics works. A floor jack with a smaller piston and cylinder will lift a weight easier, but it takes more strokes. A larger piston will lift the weight much faster, but requires more effort for each stroke.

[42merc]

Originally Posted by 19ED30

42 Merc, yr quote

I do not want to go to a larger bore because of the effort required.

You are using Disc & drum ?
On my 32 , 40 drums on all four , & you are saying the Biger bore Mc will required More effort from my leg (pushing power )
I would think Less because of more Volume,
Is this not correct?

I'm using a '72ish Mustang disc-drum M/C with a 1" bore. Disc on the front, F-100 fronts on the rear, 11"x2" drum with a 1-1/6" wheel cylinder.

Refer back to J Seery & his info about bore size & pedal effort.

Larger M/C bore needs more foot pressure & granted there is more volume.

[deuce lover]

Originally Posted by 40cpe

Would you please share the application or part number for that master cylinder? Thanks, Gene

Raybestos 39037. Napa's number is the same also.I only use DOT 4 fluid also.What's nice with this MC is that the ports face the frame side rails if your MC is pointing to the rear.Makes a nice clean brake line run.

[Bassman/NZ]

I use a 67 Mustang dual, the one intended for drum brakes, not discs. I spent forever trying to get pedal, same as you. Then one day I had a lightbulb moment and reversed the lines into the dual. Voila! There it was... instant brakes. Turns out the rears need to come in first when the pedal is depressed, I had assumed it was the fronts that needed to come in first. My brakes have been great ever since. My brakes are '39 fronts, '47 pickup rears.

[al pa.]

47 merc,front disc,rear stock drum,corvette style dual m.c.,with proportion valve,and residual pressure valves.bench bled m.c.,and hooked up both front and rear lines.did NOT bleed rear,then hook up front lines as described earlier.bled right,rear,left rear,right front,left front.Only getting half pedal.Any ideas what to do now? thx.