Brake question - Early Ford and NO residual pressure valves?

[Kevin Lee]

Picked up some brake line at lunch for my car today. Didn't think about residual pressure valves until I got back to work so I pick up the Bishop/Tardel book to see if a particular part is recommended and I can find no mention of them at all.

I'm working with Ford juice brakes - a mix of '39-'48 parts. Master cylinder under the floor. Pretty much the same setup as that roadster.

Now I stripped the brake lines from both the A frame I'm using and the '39 chassis I robbed the running gear from myself and don't remember seeing anything other than a couple of T fittings and the brake light switch at the master cylinder. So can I assume I just don't need them? Is it built into the master cylinder?

[alchemy]

Some (drum brake) masters have residuals built into them, but I've heard it doesn't hurt to have a separate one. Use a 10 pounder in the front and a 10 in the back. You are using a dual master aren't you?

Henry didn't need them because his master sat higher than his wheel cylinders. But your roadster probably has the master about a foot lower than the wheel cylinders, doesn't it? You need them to keep the fluid from draining all back into the master.


- alchemy

P.S. I have also heard that the aluminum residuals from Wilwood and the like are no good. I bought some brass ones from ECI and they are nice. Let them know what size lines you are using so they can send the correct size fittings on them.

[porknbeaner]

Kevin,
I'm tryimg to pull a number out of my head but it seems to me that drum brakes need about 7 lbs of residual pressure.
I don't know what master you're using but my '65s are both 4 wheel drums and neither has a residual pressure valve in the system. I'm assumeing that it is set up in my master.
Set 'em up without and then if the brakes don't work cut the lines and install some. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif
The most that would happen is that you would have to stroke it once before the brakes started working. Like you do when you have a little air in the line.

There that ought to prime the pump. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[36-3window]

what master cylinder are you using? some have the residual built in....39-48 fords do. if you ar not sure,put 10# inline

[Kevin Lee]

No dual master cyl. here. I crash my cars OLD SCHOOL. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif The master IS under the floor though and that floor has been dropped quite a bit - but you really think the stock location was above the wheel cylinders? I don't know man, that seems high even for stock.

Right now my guess is that it's just built in (headed to the Van Pelt site after I enter this) but even if it is I suppose adding another won't hurt. 10lbs of pressure is 10lbs no matter how many times you cut it off, right?

[36-3window]

yes, adding 10# residual valve in a system that has a master cylinder with one built in will not hurt a thing

[Kevin Lee]

I think it's ten pounds, Ben. And it looks like my resid. pressure is built in (39-48 master). So get the bender and flare tool ready. Anything else I should take into consideration?

[choprods]

It also wont do a thing....I say screw the Res'valves Just hook it up and bleed em!
I have none on mine and it has the master lower than all four wheel cyls. http://www.jalopyjournal.com/ubbthreads/images/graemlins/shocked.gif

[jerry]

the main reason for residual valves in drum system is to keep the lips of the wheel clinder cups out against the cylinder wall when the brakes are released. if you don't use them there is the chance of drawing air into the wheel cylinders.

if you have the master blow the level of the master there is the chance of all the brake fluid draining back into the master cylinder.


jerry