Proportioning valve question- wilwood adjustable versus "combination valves"

[shadango]

But , again, I need to ask....can you tell if the wheel cylinders have been upgraded by just looking at the exterior of them? Or strictly a "ya hafta pull apart to find out" thing?

[shadango]

The slave cylinders I use are the ones specified for a late '70s 1/2 ton truck.  They have a smaller diameter bore that helps with the rear brake lockup issue.

I just bought me some of these at autozone.

figured might as well be safe than sorry later.

Thanks for the advice

[Supercuda]

Externally, all of these wheel cylinders will look remarkably similar. Buy new, and you get the benefits of modern technology; buy NOS or use your old stuff, and you roll the dice and take your chances.

[shadango]

   Thats what I figured too....might as well do it right.

[brads70]

Why not this?

http://www.jegs.com/i/Wilwood/950/260-11179/10002/-1?parentProductId=1284815

Thanks for the idea Wade! I just ordered this one locally should be here Wednesday. I have the regular adjuster here now but the one you suggested looked easier to plumb in? Your getting really good at spending my money for me!

And thanks also to Changin Gears too I ordered the wheel cyl. you suggested too! As well as new calipers....might as well have everything all new...I've come this far!

[Bullitt-]

Was browsing the Summit catalog & read something I was not aware of...The switch on these proportioning valves is a brake light pressure switch, not a brake warning switch like our cars came with...Should cause no problem but don't waist your time trying to wire it up. 
 Only time I have ever seen the brake lamp lit by the valve was when I was changing out the MC.

[brads70]

Was browsing the Summit catalog & read something I was not aware of...The switch on these proportioning valves is a brake light pressure switch, not a brake warning switch like our cars came with...Should cause no problem but don't waist your time trying to wire it up. 
 Only time I have ever seen the brake lamp lit by the valve was when I was changing out the MC.

So if I wire is up to the dash brake light it won't come on when pressure is lost?

[Bullitt-]

So if I wire is up to the dash brake light it won't come on when pressure is lost?

It will come on every time you apply the brakes

[brads70]

It will come on every time you apply the brakes

Ah! gottcha!....I wonder if I could take the senser out of the stock unit and put it in this one?

[Bullitt-]

Ah! gottcha!....I wonder if I could take the senser out of the stock unit and put it in this one?

   Not a sensor, from what I can tell it is a mechanically activated switch.

    Like I said the only time I've ever seen this switch do anything is when the MC was replaced & there was NO pressure ...I'd changed front pads a couple of times before & even the bleeding did not activate so I'd think you would know you had a problem by the time the light came on.

[Changin Gears]

The stock light is activated when there is pressure on the front lines but not the  rear (or the other way around).  Your brakes will continue to work poorly.  This lets you know you are low on fluid, massive leak, etc.

[Supercuda]

The switch is the same on the other valve; it's called a pessure differential switch. Basically a spool valve that will ground the signal wire, turning on the "Brake" warning light. If you bleed brakes, and get the valve off-center, it will light up the dash lamp every time you turn the key on, or, if it's barely off, and there is a little air on the one side, every time you hit the brakes.

[shadango]

Externally, all of these wheel cylinders will look remarkably similar. Buy new, and you get the benefits of modern technology; buy NOS or use your old stuff, and you roll the dice and take your chances.

Well, as an update -- I bought two new 7/8" bore units from Autozone...installed them a couple weeks back and found one was leaking the other day...made in china....<sigh>....I went back to AZ and they are replacing it......swapped that out today.

i tore the new defective one apart and here is what I found...



It does have the spring, but no metal cups...just the pistons and the rubber seals attached to them.

Is the spring enough to compsensate for no residual valve?

I looked in my factory service manual and this is the same setup it shows for 72.....and the master cylinder that came with the car would have had the residual valves.

I am using the newer style MC so itwont have the residual valve in it I assume...



So, did I install the wrong rear cylinders?

I got the 77 dodge truck ones that were suggested....

FOund this quote on ecihotrodbrakes.com:

"10 PSI Valves - These valves are used in a drum brake system to prevent air from being ingested into the hydraulic system when you release the brake pedal. Typical wheel cylinder seals only seal when there is pressure behind them. Rapid release of the brake pedal creates a vacuum in the system which causes the seals to relax and air is ingested into the wheel cylinders. Maintaining 10 PSI in the system at all times prevents this. Some disc/drum master cylinders have 10 PSI residual pressure valves installed internally, some don't. If you're not sure, call us and we can tell you how to check. Also, some new style wheel cylinders have cup expanders which negate the need for the residual pressure valve. Either way, if you are not sure whether you have one or not, put one in. They are not cumulative and it won't hurt anything if you have two. Don't worry about brake drag, it takes roughly 75 PSI to overcome the return springs."

Hmmmm.   

I think I will bechecking with DRDiFF to see if the MC he sold me has a residual valve in it...

[Supercuda]

Don't have kitties over this; the rubber seal cup is a different material than the older ones that required the little steel "reinforcement" piece. New materials will always show up, causing some doubt and wonderment. Just soldier on with what you have; it should work fine.

[shadango]

Don't have kitties over this; the rubber seal cup is a different material than the older ones that required the little steel "reinforcement" piece. New materials will always show up, causing some doubt and wonderment. Just soldier on with what you have; it should work fine.

  Cool.   Makes sense.  (I loved the "dont have kitties over this" part! LOL)