Proportioning Valve - which one?

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Geo4K

Geo4K

Just your average Gearhead.
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I'm converting to the disc brake setup from a BBP 75 Duster, from the 10 " drums the car had on it. I was going to grab an after market pro valve, but would like a little bit of guidance from the group here, as to which one I should get. It's the only piece I haven't picked up yet.

It's a manual brake car and will keep the drums in the back.

Thank you -
 
What size drums on the back?,and What size tires ?
If your drums are 9 and tires are 225 frt/275 rear, you won't even need a valve.
If your drums are 10 and tires are 235frt/295 rear, you won't need a valve.
if your drums are 10 and rear tires are 275s, you will probably not need a valve.
The factory valve was set up conservatively for 4 same size tires.
The point is; try it without and see where you are at.
I run line 3
 
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I still have the 10" drums on the back. Also, I do have a pro valve from a KH setup. Is that of any use here? I've read around on several threads and It's just not clear. I'd rather ask and make sure, than to spend money needlessly.

I do appreciate the help here - I am an older guy, but still very young to Mopars! Thanks again
 
To my recollection, the KH system did not run a P-valve. Instead they ran the safety sw/distribution block and a metering valve to the front brakes.
However, if you truly have an oem P-valve, then feel free to run it.
But it kindof goes back to tires.
I believe you understand the purpose of that valve, and how it works. Or rather how it was supposed to work on original vehicles.
Many times with modern tires, and big-N-littles the P-valve is just not necessary and just steals stopping distance. Those big-piston calipers have a lot of power. IMO the 10"drums will have a really hard time overpowering them with tires that are two or three sizes larger than the front, without a valve in there at all.Only testing will prove my opinion tho.
I wonder if you are perhaps timid to plumb in a valve at a later date, due to the chore of re-bleeding the system?
Or I suppose you are running all tires the same size; in which case I might try that oem valve............................................
Naw, I'd still try it without. If the rear is found to be too strong, I would sooner downsize the rear wheel cylinders. And that is what I did with 235frt/245 rears.
I only ran those 245s for a short time. They just were ridiculously undersized for my power level.Eventually I was able to fit 295s back there. But I left the one-size-smaller w/cs back there.
 
OK AJ - I'm learning some good stuff here! This is what is nestled under my master cylinder, it accompaned the manual 10" drums all the way around. I had bought a complete set for converting to KH brakes - including the pro valve, but then decided that I wanted the wheel choices offered by the 4.5" pattern and went with the single caliper setup.

What is it that you are suggesting I do with this piece that came with the car? If you are saying that I may not need anything there, do you gut the insides out, keep the block place? I don't mind the work of plumbing, bleeding or any of that, I just want to do it correctly, have a fun and safe car to drive.

There won't be much of a stagger in the tire size.

Members like you all are why I come here for help and support the site. I totally appreciate your time.

George

Brake valve 2.jpg
 
George
That is nothing more than the Safety switch and distribution block. Leave it there and plumb it in. If one end of your system develops a leak, the plunger inside will move over and ground the sw, which will then turn on your parking brake lite, telling you, well if you see it, that something is amiss. There is nothing else going on inside it. I would leave it alone. Plumbing is exactly as before.
If you are gonna run same size tires all around, and if you have an oem P-valve, which looks similar but larger,you can swap it in there, and again the plumbing remains the same.That is the easiest, simplest,quickest,cheapest,and is almost guaranteed to work.
 
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