A body brake help

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ducter

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Car is a 73 dart sport. Discs in front drums rear, the PO was converting the car to a drag setup about 10-12 years ago when he moved and all progress on the car stopped(thankfully as it was a hack job). The front brakes were locked on but I found a line lock device hooked up but unpowered, giving it power managed to free one of the fronts. The rears locked up as well. I want to eliminate the line lock and hook everything back up how it is supposed to be but am clueless on how the lines are supposed to run as currently 2 lines come from the master, 1 going to the passenger side where it is T'd off going to the line lock on the drivers firewall, from that into a box(proportioning valve?) that runs to the drivers side and back to the line lock. The other heads to the rear I believe, but at the axle the line again is T'd off feeding both sides.

I am planning on buying a new lines, proportioning valve, master, calipers, rotors, pads and for the rear I imagine replacing the drums and brakes. How are the lines supposed to run? Is that box deal the proportioning valve? It confuses me as the power out from the line lock is running to it.

thanks
 
Both tubes from the MC should go to the "box", with 2 tubes from the "box" to each front wheel and a single tube to the rear axle hose. If your car originally had all drum brakes, the "box" is termed a "combination block" (I think), meaning a distribution block w/ an imbalance sense switch. If your car originally had front disk brakes (most or all 1973), the "box" is termed a "combination valve", meaning a proportioning valve w/ an imbalance switch.
 
BillGrissom said:
Both tubes from the MC should go to the "box", with 2 tubes from the "box" to each front wheel and a single tube to the rear axle hose. If your car originally had all drum brakes, the "box" is termed a "combination block" (I think), meaning a distribution block w/ an imbalance sense switch. If your car originally had front disk brakes (most or all 1973), the "box" is termed a "combination valve", meaning a proportioning valve w/ an imbalance switch.
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Thanks for the information, after a quick google search for combination valve I found one on classic industries, you dont happen to know off hand which lines go where would you?

thanks
 

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Routing on my 75 Duster...Back port of MC to top. Next 2 feed L and R front. Front port of MC to bottom front of valve. Last one goes to back an splits at block on rear.
 
Forgot.. In case your mounting is changed. That piece should be on your frame rail below MC. 1/4 turn counter clockwise if stand on driver side.
 
zkx14 said:
Routing on my 75 Duster...Back port of MC to top. Next 2 feed L and R front. Front port of MC to bottom front of valve. Last one goes to back an splits at block on rear.
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thanks for the routing info, is this how your talking about? Also, whats the last connection on top for?

thanks again
 

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Sorry, I plumbed my car with the exiting (1965) distribution block and a separate proportioning valve. I recall that some of the vendor websites give detailed info. I recall some photos from shop manuals posted here (search). My guess is that the plumbing you show is incorrect. The front and rear circuits should be on opposite sides of the imbalance switch. Probably, the left side is the rear brakes since it has 1 inlet and 1 outlet and the shiny nut holds the proportioning valve (pressure reducing). You plumb the rear to the smaller reservoir of MC (fwd). The right side is the front brakes and is plumbed to the larger MC reservoir (aft).
 
OK, here is what I tried to explain... Not as pretty as yours but here you go.

IMG_0149 (500x640).jpg
 
The other connection is a safety. This is what Bill refered to as an 'imbalance switch' and as he said that is why front and rear are on opposite ends of the valve. It grounds out to a slider inside that would shift if you lost pressure in either front or back. I'm not really sure what happens next. I think it turns your brake light on in dash, but not sure. Anyone?
 
Picture:
 

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zkx14 said:
It grounds out to a slider inside that would shift if you lost pressure in either front or back. I'm not really sure what happens next. I think it turns your brake light on in dash, but not sure. Anyone?
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Great help zkx14, and matches my guess.
The imbalance switch turns on the "brake" light on the dash. I think the same bulb is lit whenever the emergency brake is pulled, but don't know since I only had an imbalance switch on my 69 long ago.

I have read that it is tricky to adjust the imbalance switch. You must crack a line nut on both sides to let it self-center, without drawing in an air bubble. Search for posts. I think a lot of them become stuck in the center position and don't work. My pedal went to the floor once in my 69 Dart, so I was likely driving on just fronts or rears for a while, but never got a lamp warning. Maybe a prior owner disabled it because it was always lit from the switch not being centered.
 
There used to be a tool marketed, you removed the safety switch and screwed in the tool, which had a solid protrusion which kept the switch centered while you bled it.
 
BillGrissom said:
I have read that it is tricky to adjust the imbalance switch. You must crack a line nut on both sides to let it self-center, without drawing in an air bubble. Search for posts. I think a lot of them become stuck in the center position and don't work. My pedal went to the floor once in my 69 Dart, so I was likely driving on just fronts or rears for a while, but never got a lamp warning. Maybe a prior owner disabled it because it was always lit from the switch not being centered.
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This link shows one opened up, and they have the seals to rebuild them. Unfortunately I didn't find this till I had mine done.
https://www.musclecarresearch.com/1970-76-mopar-combo-valve-autopsy

My original one did not work. Was not getting flow to rear. I got a second one that was supposed to be 'good' it was crudded up pretty bad, but was able to assemble one with all the best looking parts from each. I just bled mine 'gently' till I had fluid through all lines so I wouldn't knock it off center.
Keith
 
FWIW, delete the bad diagram from this thread, lest somebody see it and assume it is correct since it is so well drawn! It will also pop up on a google search, and could lead to problems for an unsuspecting soul.
 
jimmyray said:
FWIW, delete the bad diagram from this thread, lest somebody see it and assume it is correct since it is so well drawn! It will also pop up on a google search, and could lead to problems for an unsuspecting soul.
Click to expand...

I am unable to edit the post, hopefully people will read the post.
 
So should these be replaced, rebuilt or eliminated when redoing the braking system? Mine is in place but the lines are all disconnected from the MC, actually the MC is gone. I have to pick one up.
 
If you feel comfortable rebuilding it, It will save you some money. The kit is just seals, so if any other part are bad it still wont work. I believe the complete valves are available from Inline Tube.
 
There are other aftermarket ones available, but yes you need the proportioning for the combination of disc and drum
 
Alright rebuilding as an option is good to know. Thanks for the link, looking at them on classic industries they are like a hundred bucks. Mine may very well work, just with the line lock on the fronts locked up and the rear drivers side rear locked up I have my concerns.

Also, when everything was hooked up the brake pedal was pretty high in where it sat, also very hard to push...reading around here I see where manual and power take different shafts, how would I know what I was supposed to have? I am thinking that it has the wrong MC or shaft.
 
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