Master cylinder conversion

[scooder]

Originally Posted by Heard

Tom,
I recently went through this. The only 1 1/16" mc I found was from Wilwood. Unfortunately, it just didn't move enough fluid to work correctly and I ended up using a 1 1/8" one from Summit.

When I say 'correctly', I spent a lot of time studying how a mc works and what is SUPPOSED to happen if one circuit fails. So, while the 1 1/6" mc worked OK under normal circumstances, it would NOT work in the event of a failure of either front or rear brakes. There was just not enough pedal travel in my '36.

IMO, I think the 1 1/8" one works great. The pedal effort/travel is fine for me.

But Mart is correct. Plumbing is a nightmare all to itself. I spent a lot of time on the Net and at the local parts houses trying to get all the fittings I needed. It was not fun.

Heard

I fully understand what your saying here.
I fitted a 1" dual master on my truck, this being the mustang size that's ment to be the ticket. Pedal travel was to much for my liking. When fiddling with it I cracked open the union to the rear brakes to see what would happen in a leak on one circuit situation, well the pedal went almost to the floor! Not good, has any one else tried this? It appeared to me that as I thought, that mustang one is to Small. And if they all travel this far some cars are basically gonna be left with no brakes when one circuit leaks. I say some as a lot of hotrods don't have the same amount of travel available on the pedal.
What's on mine now? A stock Ford single master, bolts in easy, plumbs easy, bleeds easy, looks right has the correct size bore, pedal travel is like I like them, about 1 1/2". If it fails, the hand brake (e brake) is spot on and works great. Better than rely on some thing that won't actually work when you most need it.
Martin.

[V8COOPMAN]

Originally Posted by V8COOPMAN

Good info rich! The only thing to possibly be careful of with a 1" bore in this case is the fact that it's going to require a longer pedal stroke to displace an equal volume of fluid as that displaced by a 1-1/16" bore, especially if one side of the cylinder ever fails. That can be a problem with the pedal geometry in these old Fords. Just sayin'! DD

Originally Posted by scooder

I fully understand what your saying here.
I fitted a 1" dual master on my truck, this being the mustang size that's ment to be the ticket. Pedal travel was to much for my liking. When fiddling with it I cracked open the union to the rear brakes to see what would happen in a leak on one circuit situation, well the pedal went almost to the floor! Not good, has any one else tried this? It appeared to me that as I thought, that mustang one is to Small. And if they all travel this far some cars are basically gonna be left with no brakes when one circuit leaks. I say some as a lot of hotrods don't have the same amount of travel available on the pedal.
What's on mine now? A stock Ford single master, bolts in easy, plumbs easy, bleeds easy, looks right has the correct size bore, pedal travel is like I like them, about 1 1/2". If it fails, the hand brake (e brake) is spot on and works great. Better than rely on some thing that won't actually work when you most need it.
Martin.

scooder ........This is exactly the situation I was alluding-to in my previous post. This CAUTION is only meant for the folks that may not understand how a dual master cylinder actually works when one side of it "goes south". DD

[john in illinois]

I tried a stock early Ford single master cylinder. It was 1 1/8 or 1/16. The pedal required too much force. When I went to 1" the brakes responded much better. This was in a model A and the pedal arm ratio may be different on other cars. I have not tried a simulated failure of one circuit. That is really a good idea.

Richard Lacy uses 15/16" in his kits.

John

[Mart]

I changed the master cylinder on my roadster from a mustang 1" unit to a 70's E250 ford van 1-1/16" unit. The pedal is nice and firm now and right in it's "sweet spot". Before the pedal was too far down. The The van unit is substantially bigger though. I just took the view that original ford master cylinders were 1-1/16" so the replacement cylinder should be the same diameter.

[scooder]

Mart, you may be ok with the E250 m/c if you have plenty of available pedal travel. It really did shock me how much extra "nothing" there was when I cracked off the back circuit.
I'm sure that in a very high amount of master cylinder convertions to twin circuit master cylinders, the extra plumbing, adapting and such is just a complete waste of time, money and effort. As in a circuit failure, the pedal will hit the floor before anything happens!
Not directed at you Mart, as I know how you think, your not a bubble pack kit form type of bloke.
the belief that as something is available in a kit, or in a glossy magazine or because that's what so and so sells, does not make it right! Stuff is sold purely because people will buy it, that's it.
Rich done his home work and studied what's going on and made an informed (well researched) choice. He is correct.
Double D also knows this.
I actually tested it.
Make um safe.
Martin.

[rich b]

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I had kinda the same experience on my '47, with the 1" bore Mustang cylinder I had lower than optimum pedal applied position and if you opened one side, it would go all but on the floor before applying the other. This did not seem like a comfortable set-up; so I picked up one of the E-250 masters that Mart mentioned. First thing I found was that this master has a longer stroke; but I thought I would play with it a little so I made a pedal pad extension so it didn't go below the floor and bled the system. The pedal apply position ended up to where it should be and when I opened either side of the system, I was surprised to find the pedal remained a reasonable distance above the floor. Have to see how this works when the car gets on the road.

I also put one of the E-250 masters on the '35 chassis I'm building; don't have the body on, so it will be interesting to see how the pedal travel works out.

I think there are quite few people with dual master set-ups that could be in for a rude awakening some day (especially the ones who don't feel it is necessary to include an operational e-brake in their build).

[rich b]

Originally Posted by JSeery

Why would you want to use 1/4" lines?

While the application pressure ends up equal with either size lines, the 1/4" lines flow more during application and release. Not so fussy with discs; but more so with drums.

Look how they plumbed production cars before they went to diagonal split
or four disc set-ups. 1/4" main lines feeding into 3/16" branches.

Early Ford Lockheeds really like 1/4" all the way just the way Henry built them.

[Mart]

One way to tune the master cylinder is to insert a washer behind the clip holding the piston in the bore. The thickness wants to be gauged so the recuperation port just about remains uncovered. By minimising the travel before the piston gets to the other side of the port means the pressure starts building higher in the pedal travel. Also the pedal free play wants to be at the minimum for the same reason. Caution is required though, because too thick a washer or no free play will stop the recuperation port from working and make the brakes stick on when things warm up.

Mart.

[Mart]

A bit of advice re ports. Napa carry the eaton weatherhead line of adaptors and the more common dual cylinders have typically a 1/" 20 port and a 9/16" 20 port. Adaptors are available to get these both down to accept a 1/4" inverted flare fitting (standard early ford fare.

Do not use the alternative method of using an oversize flare nut that puts the 1/4" pipe straight into the port. I have only ever had one brake line failure and it was in the dual MC with one of these oversize nuts. Luckily I sensed the pedal lowering as I used the brakes and limped the car home at low speed. I could see fluid dripping from the union. I reworked it with the proper weatherhead adaptor and a new pipe and all was well.

The adaptors are available for 3/16" pipe too. I have the numbers somewhere if I can find them I will post them.

I do agree with my good friend Martin (Scooder) 9 times out of 10 the dual cylinder will offer no effectual advantage. I have never tested my system to see if one circuit would still work if one end or the other went out.

I have a single circuit cylinder in my 33 and have no burning desire to swap it out. Having the dual cylinder in no way should be an excuse to keep the brakes in anything other than tip top condition.

Mart.

[john in illinois]

This is a very good thread with several issues I have not thought about. I still have to do all the brake installation on my AV8 and will use this information.

Thanks,John

[Ol' Ron]

I've done two brake systems over the past few years. Have done many hydrolic conversions in the past. I came to the conclusion that just adding a hydrolic cylinder doesn't improve the braking of the car. Using the 39-48 system doesn't improve the braking of the vehicle, it only makes it easier to push on the pedal. Many guys will tell you the old rod/cable systems worked just as well, when in good condition. With hi-way speeds of today you should consider up grading to disks in the front and save the old systems for parades.

[V8 Bob]

Dual master cylinder discussions come up often, and usually with some confusion and/or lack of understanding of how or why they work; kind of troubling as they have been available since at least 1962, and USA mandated in '67

There are three basic items that have to be taken into account when installing a dual master on a non-stock/custom application; bore size, M/C stroke length and pedal ratio. The M/C has to be able to be fully stroked before the pedal runs out of travel, period. If total stroke cannot be attained, the safety function of a dual M/C may not be available in the event of a system failure. The brakes also have to be assembled, adjusted (if applicable) properly and in good condition.

I know for a fact dual masters work as designed, as I spent most of my working life dynamically testing dual brake systems, and they will work 10 out of 10 times if set up properly. (Sorry Mart) Much better to have a partial loss of pedal and one axle braking, v.s. NO brakes in the event of a line/cup/seal failure. No amount of maintenance can insure a hydraulic failure will never occur.

[Mart]

Agree with everything you say Bob, They will work properly 10 out of 10 times if set up correctly. The point I was trying to make is that when retrofitting to an early ford or a previously mechanically braked setup converted to hydraulic they are probably not setup properly. An OEM car maker will design the pedal/cylinder/rest of system to make sure the required travel is available. That may mean making sure plenty of spare pedal travel is available beyond the normally used travel. More easily accommodated when starting with a clean sheet of paper design.

A modified early ford setup hasn't had that extra travel designed in and that was why I made the statement.

I hope I'm wrong and if someone should suffer a partial failure they do manage to come to a stop safely. But unfortunately I was sort of agreeing with a previous point that people may believe they have increased the safety level of their vehicle but in reality that belief may be unfounded.

Mart.

[Talkwrench]

Originally Posted by V8COOPMAN

Good info rich! The only thing to possibly be careful of with a 1" bore in this case is the fact that it's going to require a longer pedal stroke to displace an equal volume of fluid as that displaced by a 1-1/16" bore, especially if one side of the cylinder ever fails. That can be a problem with the pedal geometry in these old Fords. Just sayin'! DD

This is why in the end I kept the single circuit original setup. In saying that I have a new USA made m/c all new lines I made, new wheel/ cyls too. And have just recently added a VH 44 power booster, It works well.

[V8 Bob]

Originally Posted by Mart

A modified early ford setup hasn't had that extra travel designed in and that was why I made the statement.

I hope I'm wrong and if someone should suffer a partial failure they do manage to come to a stop safely. But unfortunately I was sort of agreeing with a previous point that people may believe they have increased the safety level of their vehicle but in reality that belief may be unfounded.
Mart.

Mart, I am using a 1" bore disc/drum Mustang M/C on two vehicles; a '51 with stock pedals, and on my '32 with '33/'34 pedals; also a 1" F-250 disc/drum M/C on my '40, and all three masters will bottom out before the pedals, so I know it's possible with old Ford pedals. The pedal has to return fully with it's own spring, along with minimum push rod clearance of about 1/16", and careful use of carpet padding to enable full stroke.
Confirming a full stroke is possible, then bleeding one axle at a time and checking brake operation (as mentioned earlier) will ensure the safety advantage of a dual braking system.

[scooder]

If carefull carpeting makes a difference, your getting damn close to the floor! That's to close for me, add a smidge of unadjusted wear, little bit of fade, it's at the floor!
Why not fit a bigger bore master cylinder and have some much needed comfort room? Surely you can understand this would be better and safer?
Martin.

[V8 Bob]

Originally Posted by scooder

If carefull carpeting makes a difference, your getting damn close to the floor! That's to close for me, add a smidge of unadjusted wear, little bit of fade, it's at the floor!
Why not fit a bigger bore master cylinder and have some much needed comfort room? Surely you can understand this would be better and safer?
Martin.

It's called compromise. There are several factors that have to be weighed when designing an apply system, and among them are comfort, seating location, pedal efforts and M/C operation.
Close to the floor is fine as long as you can fully stroke the master. Wear and fade won't change the total stroke available, as many OE vehicle's pedals will also be "close" to the floor during a full stroke check. Floor carpet doesn't have to be 1" thick to be comfortable, especially around the pedals.
Going to a larger M/C bore will increase pedal effort, without ratio change, and has to be considered. Keeping a manual system around 50 lbs. or less pedal force for most braking is a good target.
A few vehicles will allow a long brake pedal to stop well above the floor without looking or being awkward, but most will not.

[V8COOPMAN]

[QUOTE=V8 Bob;1013445]It's called compromise. There are several factors that have to be weighed when designing an apply system, and among them are comfort, seating location, pedal efforts and M/C operation.
Close to the floor is fine as long as you can fully stroke the master. Wear and fade won't change the total stroke available........ QUOTE]

Everything V8 Bob states above is gospel. The most-IMPORTANT part of the statement is a TOTAL and clear understanding of what the term fully stroke the master means. As Bob says, if your installation is not capable of "fully stroking the master" BEFORE the pedal mechanically runs-out of travel, the DUAL-master-implied redundancy will not be possible if pressure is lost on one circuit in the dual system. DD

[funrunr]

V8 Bob, did you have clearance problems with the F250 MC in your 40? I used a 69 mustang in mine and had to cut the cover and weld flat. Otherwise is too tight to the floor and cannot remove the lid/cover.
Other than that the brakes work fine and have disc/drums.

[scooder]

Bob, sorry missed the bloody obvious full stroke.I'm not nit picking here, I'm just making sure we have the hole picture.
If the master cylinder bore is to small, is it possible that it will work "fine" with both circuits operating as they should, but in a one circuit fail, the master cylinder can't displace enough fluid to operate the one circuit now doing all the work. Irrespective of the ability to full stroke?
I'm still uncomfortable with using a smaller bore master cylinder than the original one, all else being equal.
I get your compromise bit, and I spose it's what your used to. I only drive old stuff, and work on old stuff. I'm used to brakes that you have to stand on, and I'm comfortable with this. When I have the misfortune to drive something "new" (read built from 1980's on) I'm shocked at the brake sensitivity. Read kiss the windscreen.
So pedal pressure isn't really a "given" what's ideal to some is unacceptable to others.
What say you.
Thanks
Martin.