So I'm just about ready to plum my drum brakes for my jalopy pick up, and would like to know how YOU professionals would do it. They are 53'-56' F100 drums up front with stock internals, mid to late 60's Ford 9" rear drums out back with stock internals, and dual resevoir master cylinder thats frame mount. I'm planning on steel lines front and back. Do I need a residule valve for the rear, if the wheel cylinder is below the master? And do I need proprtioning valves both front and back, and what kind of pressure for each end? Thanks for your input.
Just make sure that your MC is set up for 4 wheel drums; if not you will need the residual valve for the end of the MC that's not for drums as drums require some pressure to help keep the wheel cylinders from collapsing and requireing more pedal effort (movement) to get them to engage. You should only need 3-5 psi to keep the wheel cylinders happy. Of course I'm sure you'll get more "expert" advice on how to do this...
If you're using an older style drum master cylinder, you should be fine without adding any extra valves. The rear might have self adjusting brakes, the front probably does not. I'd either take the adjusters out of the rear, and get the older non-self adjusting star wheels etc for the back, or else get the newer hardware from a late 60s truck for the front. So the front and back are the same.
If your car is raised or lowered or set at an odd angle or if you are not running brakes that are stock or at the very least all from the same vehicle I would suggest an adjustable proportioning valve. If you are running a lowered vehicle with a significantly altered center of gravity for instance you can run more brake bias to the rear brakes. A lowered vehicle doesn't have near the tendency to dive when the brakes are applied and can use more rear brakes. It will give you better stopping power. A raised vehicle on the other hand has a tendency to lean harder on the front wheels and you want your rear brakes to not lock up so you would run less bias towards the rear brakes. let me give you a real world example: I am setting up the brakes on an early '60s gas class car. The front will set slightly higher than stock because of the engine setback and less weight on the front suspension. It is running 12" buick drums on the rear and period discs on the front. On the big end @ 120 give or take the nose is going to dive hard. That is going to take some of the weight off the rear. Now given the combination of big rear brakes and dive the brake bias will need to be mostly on the front brakes, if not the rears are going to lock up and slide, not your optimum situation. Does that make any sense at all?
Most/all pre-70's drum brakes require residuals, so check the master cylinder you are using (do you know what master you have?) for internal residual(s) at the outlet ports before adding 10# in-line residuals front and rear. You should not need proportioning with drums all around, unless brake/wheel cylinder sizes are way out of balance. What size are the rear brakes and cylinders? (Most 9" rears came with 10" or 11" drums) You state you will use steel lines, but what other kind of hard lines would you use? Just curious.
The master is from Speedway so it's new, and the drums are the same size 10". It's going to be on a roadster pick up that isn't really lowered other than a suicide perch with spring on top up front, and a high arch model A rear spring with a few leafs removed. Also the frame is Z'd in the rear only about 6". I didn't go for the slammed look, more of a late 50's hot rod stance. The steel lines refrence is because some people use fancy stainless steel lines wich require different flared fittings, and I don't know if there is a difference in setting them up compared to mild steel lines.
You can check the master for residual checks by probing the outlets with the dull end of a small drill bit, if there is a rubber disc behind the brass, there are checks, if it goes in you will need to add them in line. Be sure to attach your steel lines securely and mount the rubber hoses in the proper brackets. Make sure they do not rub on anything through full suspension movement and permit left and right turns lock to lock without getting pulled tight. If you are not familiar with adjusting drum brakes, take a little time and learn about them. It is not complicated; but needs to be done correctly. Also make sure the master cylinder push rod is set with the proper clearance. When you get everything going with no leaks, do a few test stops, increasing speed and braking pressure until you are comfortable with how the car reacts. The brakes will wear in and stop better as you put miles on them. If the brakes are not self adjusting, remember to adjust them. Be sure to hook up and adjust the emergency brakes and see that they actually work, you never know when they might come in handy.
Ok so I've concluded from everyones info that I need to run a residule valve, either in the master or in-line if one isn't in the master. So how about porportioning valve? If I have 11" drums up front and 10" drums out back do I need one, two, or none at all. If I do, what is the common setting(s) for pressure?
67 was first year for dual mastercylinders.get a manual brake drum/drum mastercylinder for a 67 mustang. most of the dual mastercylinders sold now are the large corvette type that are only for disc brakes.
It keeps the brake fluid up in the wheel cylinders instead of running back into the master. It's basically a "back-flow" preventer. That way you always have brakes ready to stop you.
So 10 for front and back? I was thinking of putting only one on the back at 10#'s and nothing on the front since that is where most of the braking happens.
I've put several drum/drum cars together over the years, never found the need for a proportioning valve. Of course, others will have a different idea on the subject. Just saying.
Ok I was hoping someone would chime in about not using them. I'm planning on trying it without them. Thanks for the input.
everyone has their own idea, and brakes are a really touchy subject, no pund intended. being frame mounted m/c rule of thumb, you should run res. valves. you'll be fighting the gravity and the wheel cylinder pressures, with bleed back to the m/c. i suppose you could try a drum drum m/c off something like a Cadillac, that would have big enough prop balance built into them, and be able to handle the amount of fluid transfer that your large diameter wheel cylinders capacity have. as mentioned above id still run a adjustable prop. valve, so you can adjust the rear line pressure. i like to use the wilwood ones. they have one that i use that incorporates a brake light switch, prop valves and is adjustable for the rears all in one little package. all the lines are 3/16 also. http://www.speedwaymotors.com/Wilwood-Adjustable-Proportioning-Block,41747.html
Alright thanks, it sounds like I had the right idea of how to do this. Check for residual valves, and install a rear proprtioning valve set at about 10#s. I will post my results in my build thread when I finally get there. Thanks again.
The proportioning valve doesn't regulate pressure in a fasion that it can be set at a certain pressure. That comes from your residual pressure valve. The proportioning valve regulates the percentage of brake fliud that goes to one end or the other. Look at it htis way, they say that a vehicle does 60% of its brakeing with the fronts, you use the proportioning valve to regulate that. More often than not for drums we use 7 psi for drums.
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