Technical Removing Residual Valves...

I've been slowly rounding up the parts needed for the brake upgrade on my '60 Sunliner 'vert, as money allows y'know... LOL. Other than some lines, hoses and the other inevitable small parts that always seem to turn up, the last piece of the puzzle appears to be the master cylinder.

The PO had already split the brake system using a typical late '60s-70s Ford master, but it's for a drum application with residual valves in both circuits. As I'm going with 4WDB, those need to be gone. Now the usual fix is to use a Corvette-style master, but I'd like to keep the 'Ford Flavor' so that will look out of place. That style of Ford master in a 4WDB configuration was never all that common and the ones that were used have seemed to have gone obsolete and are NLA.

So the master I have is configured right, except for those valves. In my research into this, I ran across a post on another site where the guy pulled them out of his drum-brake master. The method used was to run a screw into the fluid port in the brass seat then simply pry them out. The valve is behind the seat and can be fished out. As long as you don't damage the sealing surface on the seat, just press it back in and you're good to go. Looks simple....

Anybody else done this? Any reason why this wouldn't work?

 

The one time I did this, I tapped the hole in the seat and used a machine screw and spacer to jack it out. It was so simple even I could do it

 

The seats can also be removed by carefully using an easy-out.

 

I have done it the same way Doublepumper used. worked quiet well for me also.

 

A screw , in a slide hammer , and they come out easily !!!

 

So disc brakes use abbreviated description even though drum starts with a D as well? Had me confused for a while there.

 

What bore master cylinder do you need?

Pulling them out does work, but you do need to be careful.

I would actually tap the hole for screw threads, rather than just jamming a screw in there.

You want to do this in a controlled fashion.

 

"Controlled fashion?? Controlled fashion?? This whole board is out of control!!"

 

I have done the same. Tapped the brass seat then long, I want to say 8-32 screw and a stack of washers. They come out easy. Pull the rubber flapper valve and spring then Lightly tap the seat back in and you are done.

 

The late model Ford mast will work if you can stand the plastic reservoir. I used the 67 Corvette manual master on the Fairlane.

 

years ago when overhauling the MC in a drum/drum car with a dual cylinder, the kit came with new residual valves, and seats, and yeah, you were instructed to use a screw to get the seats out. I guess modern kits may or may not come with new seats, or the kit might just no longer be available.

Have fun, I think you'll get it figured out and working

 

Thanks for the replies, I now know this isn't some sketchy fix with hidden pitfalls. Looked simple and pretty much idiot-proof, but you never know...

 

Well, here comes another food fight.

A DRUM/DRUM MC is not designed to operate FOUR WHEEL DISC. The reservoirs are not large enough and the bore size(s) will be different.

You want a FORD style cast iron DISC/DISC MC?

What are the brakes off of? Power or manual?

 

I'll have to disagree, as a proper functioning brake system the actual amount of fluid transferred from the reservoir when you operate the brake pedal is very small. Then fluid returns to the reservoir when brakes are released. The larger reservoir just provides more if there is a leak before sucking air.

Brakes operate more on pressure than volume of fluid. Yes some volume is used when pressurized, but pressure does the work.

 

I always thought the larger reservoir on the disc side was to accommodate the larger amount of fluid held in the calipers as the pad wear. Especially for Joe Public that doesn't look under the hood and check levels like responsible hot rodders do

 

^^^^^ This. To be sure enough make up fluid is available as pads wear is the only reason. Caliper pistons do not return home like wheel cylinders do.

 

That's it... that's the 'brake adjustment'. Now finding a disc/disc master with equal size reservoirs beside the corvette unit isn't all that easy, particularly in the Ford earlier style masters. I've found plenty that are claimed to be disc/disc ready but are using the 'regular' big/little reservoirs, and if you dig into the fitment guide for some of them, they can also be used in a disc/drum system so those are suspect. The only Ford disc/disc master of this style with equal reservoirs I've personally seen is the one used on the Versailles, Granada and Monarch and they're obsolete and NLA. Not that it matters; Ford rotated the mounting bolts about 30 degrees from horizontal and if not installed on its matching hydrobooster it'll be leaned over.

But I have seen equal-sized reservoirs in some earlier drum-only master applications, which one reason I asked the original question. I still have to check bore sizes, but I'm confident I can find a suitable unit... once the residual valves are removed.

There are later-model masters that will work as-is, but I don't want a plastic reservoir...

 

FWIW. I screw around with OT Fox Chassis Fords.

'85 Lincoln Town Car MC is 1" bore (7/16"-24; 1/2"-20)
'85 SVO Mustang is 1-1/8" bore (9/16"-18; 1/2"-20)

Both use the conventional large/small reservoir, and the SVO used 73/54mm calipers.
Reservoir volume is not a problem. I didn't want to change the under hood look either so I used the Lincoln Log MC on my OT Fairmont with Cobra brakes(2x38mm/1x38mm)
If you get lucky you may be able to find a rebuilt Lincoln TC unit which looks like the older Fe units but its AL, save a few pounds.

 

OK, let me try it this way -

Why does OEM use a larger reservoir? How much fluid is needed to push a wheel end caliper piston over a wheel cylinder pistons?

But I have seen equal-sized reservoirs in some earlier drum-only master applications

Well that is called a drum/drum dual reservoir MC. You have differing types of dual piston MC's and for good reason -

-DRUM/DRUM
-DISC/DRUM
-DISC/DISC

Where does MC bore size come into play, pedal ratio, manual or power assist?

I have no dog in this food fight. Just trying to warn.

... OUT ...

ADDENDUM - (Fr. For I Forgot)

The DISC/DISC MC bowl sizes may vary (large front rsvr - smaller rear rsvr) as the rear disc does not have an overly large piston(s) as do the front and do not need the extra volume.

This is why you need to attempt to balance the braking system (FRT to RR bias - brake sizing) as does OEM when performing a DISC/DISC upgrade.

 

For legal reasons. It’s like “Caution Hot Coffee” kind of a thing.

 

Not sure if this is what you are looking for, but Oriellys shows one available for an 80 Versailles made by Brakebest...........

 

That's for the 'base' disc/drum brakes. The optional disc/disc use a different master....



The bottom pic shows the deal-breaker....

 

That looks like it has enough flange to drill two holes on the horizontal line that crosses the bore.

Either that, or make an adapter plate.

 

OK, let's take this in pieces....

There are four basic mechanical differences in most master cylinders. They are:

Reservoir size. This doesn't really matter, that's been explained already.

Bore size. Again, this really doesn't matter the way you think. If there was any large difference between front/rear brake application in terms of fluid volume displacement or pressure, a two-size stepped bore would be needed and those aren't common at all.

Piston stroke in the master. This is directly related to bore size. For a given amount of stroke, a smaller bore will displace less fluid, a bigger one more. A smaller bore will also develop higher pressure with a given amount application force, the bigger one less with the same force.

These last two items are what you 'size' when determining master selection. The bore needs to be large enough to displace enough fluid to apply the brakes, but small enough to avoid too-high pedal application force, also without bottoming out before full application is achieved. There is no 'standard' for drum, disc or mixed systems, each one can have different or same requirements depending on other factors. Manual brakes you try to reduce the pedal effort, power-assist brakes can tolerate higher effort as the assist will take up the difference. Most drum brake assemblies are a self-energizing design allowing for less pedal effort, discs don't do that so need more effort.

This leaves the last difference between a drum circuit and a disc circuit in the master, and that's the residual valve. If it's a drum system, the valve is used to supply a 'pre-load' pressure at the wheel cylinder to reduce stroke before building pressure. Remove the valve and it's now a disc circuit, no preload needed. So if you take a drum/drum master and remove the residual valves, it's now a disc/disc unit.

And to sow further confusion, let's talk about those OEM-style brass 'proportioning' valves all the aftermarket disc kit suppliers want to sell you for $50, with the attending hassle of plumbing them in. What do they actually do? These have three supposed functions: the proportioning valve, a pressure-differential valve/switch for a warning light, and a 'metering' valve.

The proportioning valve is there to supposedly 'balance' front/rear braking. The problem here is the OEM's have literally dozens of variations of these assemblies, each tailored to specific applications. AFAIK, the aftermarket only sells two 'generic' versions. The chances of the 'proportioning' being accurate for your combination is somewhere between slim and none IMO. In reality, all you're really trying to do is prevent the rear brakes from locking up before the front brakes, which if that occurs will cause the car to swap ends. Sizing the brakes properly will prevent this.

The pressure-differential valve is only there to turn on the warning light in split systems in case of pressure loss in one circuit or the other. Unless you install a light, it's useless. I have had these cause other issues...

Leaving the 'metering' valve. This is there to slightly delay the application of the front brakes to allow the rears apply first, theoretically preventing front brake lock before the rears. This may or may not be useful, I've removed these valves from systems before with no noticeable difference in braking performance. If this is something you feel you really need, a two-piece piston assembly in the master will do the same thing without the complication of the full valve assembly. The only requirement here is the master has to be configured with the front half operating the fronts and the rear half for the rears. Ford commonly has this reversed on their masters, this seems be typical on others too. This is where a 'converted' drum master with two equal reservoirs will be a better choice.

 

I looked at that, but why bother when a converted drum/drum master will do the same thing for less money/hassle? The only real gain here is a bit larger reservoir, no problem if you check the fluid level regularly.

 

Really? Where?

Well, actually there are.

Well, not really.

Enough.

Somebody needs to break out a brake theory/text book, especially concerning a METERING VALVE, bore diameters and piston travel.

Personally, if one wants to bust his ass and cause a lot of damage, that is his/her/it's/mutant's choice, The scary part is that this modified braking system might be on the road where I and/or family is driving.

You guys proceed. I have been scared enough.

 

Just can't leave well enough alone and keeping rattling cages ...

The MC you showed is for HYDRO-BOOST. That is why the bolt-on pattern. Most FORD DISC/DISC SYSTEMS are HYDRO-BOOST and that is for a reason.

I really think all here should get together and write FORD ENGINEERING to inform them that they have been over complicating braking systems design all along. Maybe even suggest a one design MC for all applications. Bet that would make the bean counters happy.

 

I though those old Fords came with nice wide 11" or 12" rear drums.

I always had the best braking performance with disc up front drums in the rear.

 

Maybe This Will Help, Maybe Not ...

- 1300HP MERC COMET BRAKE FAILURE -​

https://www.reddit.com/r/cars/comments/vups2d/1300hp_mercury_comet_crashes_due_to_brake_failure/

And A Follow-Up -

​

 

Not to complicate things, but maybe ECI, Wilwood, etc can set you up.
Plastic reservoir aside, the folks who make a living off it ight be the route to go.
As an aside (because I surely don’t know) if you take out the valves in the MC you have, what else needs to be done?