WHO'S GOT THE SCOOP ON RESIDUAL VALVES?

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CFD244

CFD244

"THE NEW OLDSMOBILES ARE IN EARLY THIS YEAR"
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Hi Folks

1971 Demon with OEM 10 inch rear drums and KH discs.

I Bought 2 master cylinders for the above application. One MC came with no residual valves and one came with 2. Both mc's have the large and small brake fluid reservoirs.

The system includes original wheel cylinders and original proportioning valve. I plan on using the mc with no residual valves......Should I install the residual valve in the rear brake outlet or leave it as it came.

***On a side note, I have 2 masters from a 1993ish pick up with disks up front and drums in the rear. There are no residual valves in either port on both masters.***

What say ye?

Thanks FABO
 
I have heard that some newer wheel cylinders have built in residual valves or something that makes the valve unneeded.

If it was me I would look for a proper replacement, or see if you can get a valve and seat and install in the mc.

ALSO ..
my research shows that the 1" mc for the application has been out of production for some time. Used or NOS are the only options. Not even rebuild kits.

There are 15/16 and 1-1/32 masters available
 
Dana67Dart said:
I have heard that some newer wheel cylinders have built in residual valves or something that makes the valve unneeded.

If it was me I would look for a proper replacement, or see if you can get a valve and seat and install in the mc.

ALSO ..
my research shows that the 1" mc for the application has been out of production for some time. Used or NOS are the only options. Not even rebuild kits.

There are 15/16 and 1-1/32 masters available
Click to expand...
Manual says 1 1/32 for my master......I've seen the Dorman number posted here somewhere for the 1 inch master bore.

I was thinking of using the disk residual valve in the one mc, in the drum section of the other. Then I'll have 2 mc's with residuals in the drum sections, and nothing in the disk sections.
 
The spring in the wheel cylinder between the cups makes the residual valve in the Master cyl, redundant, not nec.
So, if the wheel cyls have a spring, you don't need the residual valve in the m/c.
 
Inertia said:
The spring in the wheel cylinder between the cups makes the residual valve in the Master cyl, redundant, not nec.
So, if the wheel cyls have a spring, you don't need the residual valve in the m/c.
Click to expand...
That makes no sense. They have ALWAYS had springs. I was taught that drums need residual, disk do not. There are sometimes exceptions, I was told depending on master cyl. location, IE older vehicles under the floor boards.
 
67Dart273 said:
That makes no sense. They have ALWAYS had springs. I was taught that drums need residual, disk do not. There are sometimes exceptions, I was told depending on master cyl. location, IE older vehicles under the floor boards.
Click to expand...

The residual pressure valve was designed to hold enuff pressure to keep the wheel cyl cup "lips" in contact with the cyl wall, to prevent fluid loss while not in use, - was what I was taught, and was in my Red Seal Manual.
Look it up .
Newer design wheel cyls came out with the spring, originally iirc with a formed cup on the ends to push the cup lips into contact, preventing fluid loss .
I just got thru doing a 67 Barracuda brakes, 9 inch drum
No springs in the wheels cyls.
 
If you look at 69 up rear backing plates, they have 2 tabs on either side of the wheel cylinder. My understanding is they are there to keep the pistons from popping out until the shoes and springs are installed.
 
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