eliminate proportioning valve??

[dustoff440]

I am going to adapt a late model aluminum m/c to my 70 Dart, Can I safely eliminate the prop valve all together by putting adjustable pressure valves on the front AND rear line. Stock KH front discs and stock rear drums for 8 3/4. I plan on using one that has a 1 1/8 bore and putting 7/8 bore wheel cylinders on the rear. And experiment with settings till I get it where I want it??? That it has a warning light means nothing to me.

 

[340sFastback]

With a 1 1/8" bore the leg effort to stop the car will be excessive. Even with two legs on the pedal it will be very difficult to stop the car. Go with a 15/16" bore master cylinder for reduced leg effort. 7/8" rear wheel cylinders good. Go with adjustable proportioning valve in the rear brake line.

 

[dustoff440]

With a 1 1/8" bore the leg effort to stop the car will be excessive. Even with two legs on the pedal it will be very difficult to stop the car. Go with a 15/16" bore master cylinder for reduced leg effort. 7/8" rear wheel cylinders good. Go with adjustable proportioning valve in the rear brake line.

ok i'm good with what you said, but I'm not sure if I fully understand.....can I eliminate the stock prop valve if I do that

 

[340sFastback]

The stock proportioning valve is about 12" back on the frame rail to the rear of the distribution block. Yes you can replace that stock proportioning valve with an adjustable proportioning valve.

 

[dustoff440]

ok i'm good with what you said, but I'm not sure if I fully understand.....can I eliminate the stock prop valve if I do that

ok. the 7/8 D100 rear wheel cylinders should cease the famous lock up, the 15/16 with the rest of the stock set up except the valves should provide some travel but not minimal travel and not a hard pedal like the 1 1/18...

what about the pads, should I get the most heavy duty with the metal chips??...same for the rear shoes??

Ive been told that DOT5 is not the way to go with an older set up like this one that ( was told DOT 3) the the 5 can actually cause damage if the unit was not designed for it...

last question, do you have a recommendation for a 15/16 bore aluminum m/c??

Sorry for all the questions, to me that most important items on a fast street car are the brakes and steering, I want them to be jam up with absolutely no question that they are REALLY good

Thank you very much, Brooks

 

[67Dart273]

You may not HAVE a prop valve now, if the car was originally all drums it did not. It MAY just be a combo distribution block/ warning switch.

Normally you NEED a prop valve in the rear line. You can buy adjustable aftermarket through Jegs, Summit

 

[green1]

add to dot5, just bleed the whole system. Put valve on rear line, test and adjust. If original drums, leave it. And smaller m/c bore easier on the leg.

 

[340sFastback]

You can read what I did to my brakes here:

http://www.billsgarage.info/BarracudaBrakes.shtml

And yes you will still need the adjustable proportioning valve in the rear brake line even wit the 7/8" rear wheel cylinders.

I would run standard rear brake shoes. Just get a name brand quality set. Front brake pads I run EBC red. The KH disc brakes need all the help they can get.

 

[BillGrissom]

I recently got an adjustable prop valve for $28 from Jegs via ebay. I mounted mine high since don't have the warning switch setup you have in 1970. Don't believe the strange stories about DOT 5 problems. It is less likely to degrade any components in your brake system, including rubber seals. Indeed, some British race cars in the 1950's required silicone brake fluid since glycols attacked their seals. The U.S. military uses it. Just don't use it in an ABS car. Not sure that really matters, but manufacturers say not to.

Note that DOT 5.1 is not silicone. It is regular glycol and will rust and remove paint similar to DOT 3 or 4. It is the first glycol to meet the higher DOT 5 standards. They are required to call it 5.1 to not confuse with silicone, though that certainly confuses people.

Don't believe the strange claims that you can't mix glycol and silicone or else mysterious bad things will happen. That was even tested and found to be bogus and absurd.

Don't fall for Valvoline's DOT 4 "synthetic brake fluid" marketing. All brake fluids are synthetic (i.e. man-made).

 

[dustoff440]

I recently got an adjustable prop valve for $28 from Jegs via ebay. I mounted mine high since don't have the warning switch setup you have in 1970. Don't believe the strange stories about DOT 5 problems. It is less likely to degrade any components in your brake system, including rubber seals. Indeed, some British race cars in the 1950's required silicone brake fluid since glycols attacked their seals. The U.S. military uses it. Just don't use it in an ABS car. Not sure that really matters, but manufacturers say not to. Note that DOT 5.1 is not silicone. It is regular glycol and will rust and remove paint similar to DOT 3 or 4. It is the first glycol to meet the higher DOT 5 standards. They are required to call it 5.1 to not confuse with silicone, though that certainly confuses people.

That's good to know as a I want the best when it comes to braking and don't mind spending xtra on steering and braking, how dd your valve installation work out. Thanks for the heads up on the price, I had done some preliminary price checking and was only down to $43.

 

[BillGrissom]

I installed the adjustable prop valve beside the booster. I had a bracket from an Intrepid booster that worked perfect. It uses the 2 holes that mount the MC (photo). I haven't wired the "low fluid" switch yet since there is no factory dash light to use in my 65 Dart.