Brake question

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Tim...Ok

Well-known member
Joined
Oct 27, 2010
Messages
1,185
Location
Inola,OK
Sorry for the stupid questions, but most of my "builds" have been hopups and engine swaps,never built from nothing before..

I'm doing a 90° under dash master cylinder on my truck project..I understand the benefits of adding an adjustable proportioning valve inline..But my question is what is it the factory put on most vehicles..I assume its similiar but nonadjustable? Just not real sure.. Here is the one from my 82 chevy,I don't know the function of it, but do I need to add one, or is just an adjustable aftermarket valve plenty?

brake.jpg
 
I've never run a proportioning valve because my cars never have disc brakes. My Son Don is running one on his T bucket because he has drums rear and discs front and the fronts were not getting enough juice compared to the back.

With drum brakes and a high master cylinder you really don't need residual valves either, just if the mc is under the floor and lower than the wheel cylinders. My 27 has the mc under the floor but higher than the wheel cylinders so I have never put a residual valve on.

You can simply bring your lines down from that underdash mc and run one line forward and one rearward and it will work fine. That is how it is on my Son Dan's rpu and how I will be doing my rpu with the same setup.

Don
 
I put an adjustable one on the rear brake line of mine, but I ended up running it wide open - basically didn't need it. I have discs front & rear.

I just put disks on the front of my Fairlane and again don't need the proportioning valve. The fronts lock up before the rear drums.

"they" say if you have bigger tires in the rear than the front, it will mostly negate the need for a prop valve. I say just spend the $30 and put one in your system. That way if you need it, you can use it. If not, just run it wide open and it won't hurt anything. Beats taking it apart, adding one and re-bleeding later.
 
I put one in my drum system and it was pretty much a waste of time and money, I run it wide open.

What I did not do was put in RPV's as I thought my master had one.

After bleeding the lines and having really tight brakes the first day, the next day my pedal was a little soft.

A few days after that it was really soft.

I went to the furthest wheel cylinder and got air out as I unscrewed the bleeder.

I now have the fun job of adding RPV's in a completed, or so I thought, brake system.
 
I put one in my drum system and it was pretty much a waste of time and money, I run it wide open.

What I did not do was put in RPV's as I thought my master had one.

After bleeding the lines and having really tight brakes the first day, the next day my pedal was a little soft.

A few days after that it was really soft.

I went to the furthest wheel cylinder and got air out as I unscrewed the bleeder.

I now have the fun job of adding RPV's in a completed, or so I thought, brake system.

Is your MC under the floor? I've read many times that you need RPV's if the MC is at or below the wheel cylinders..

Tim
 
The factory porportioning valves are designed for a specific chassis and weight. Changing to larger/ smaller brakes or different size master cylinder will effect the porportioning valve balance. You may not need one but leave enough room to install one. If you are running drum brakes, some of the dual master cylinders have residual valves built into them. I have a pontiac lemans master on mine, mounted below the floor. After three months sitting. I had a full and firm pedal with no residual valve (drum/drum).
 
thanks for the replies..If you see a problem with this plan, please let me know..I have disc brakes on the front using 78 chevy truck calipers,9" rear with ford truck drums and a new 78 chevy truck MC that will be mounted up high under the dash, gonna try it with no proportioning valve and see how it acts,be easy to add one later if i need it..

thanks,
Tim
 
A lot of good advice here.
I set my brakes up with disk all the way round, most of the time and never use a proportioning valve.
I use large calipers in the front (large Gm) and smaller calipers in the back (metric GM).
On the Disk front drum rear I still don't use a proportioning valve.
If I want an anti-lock rear brake system I use a non adjustable Stewart anti-lock valve in the main line feeding the rears.
On hard, quick braking it will not lock the rears on initial braking but, will allow full pressure gradually. This works extremely well for disks or drum :D
Here's a link to what I'm talkin about Hope this helps.
http://www.73-87.com/7387garage/chassis_suspension/lbs.htm

Jim
 
i know every one here is offering good advice, i also want to add my 2 cents.... i studied everything i could find from the internet from "reputable" sources, i then used what i had with what i knew i needed... it also took a little tweeking to get the air out and adjustments etc....
my system consisted of a hodge-podge of parts.. from a camaro front clip w/discs, a camaro rear (same yr as front) with drums...running a ford explorer booster under floorboard and mastercylinder... i used a ford f-150 proportioning valve and used risidual valves as well...

it has absolutely no trouble stopping my truck! and that, no matter what you use, is the goal of any brake system...:cool:
 
and that, no matter what you use, is the goal of any brake system...:cool:
I sure agree with that..and thats all I'm after..I want my tires to be the limiting factor in my brake system and not anything in my brakes themselves..I know on my 82 Chevy that I pictured above, I put a 9" rear with discs in it and didn't change anything,and it stops great..thanks everybody for the replies and help..

Tim
 

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