My 69 valiant now has all the brake parts from a 74 dart except the following - lines, prop valve, and rear drums

On to the problem. I cannot get a good pedal. It has to be pumped a few times before a hard pedal is felt.

We bled the master cylinder before we put it on and then bled the front calipers. The drums were bled before we put the master cylinder on. I think we still need to bleed the rears again, but I have not yet.

• - Is the older drum style prop valve going to keep it from getting a good pedal?
  
  - If there was air in the lines to the rear drums, would that cause the pedal problems I am having?
  
  - Should I get the adjustable prop valve from summit or wilwood? - they are about $38

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69 valiant

Pretty much, when you change the master cylinder, you should bleed afterwards to make sure there isn't any air in those rear lines. I can't remember the cutoff, but there were certain years (pre-74) where the prop. block actually has a bleeder orifice and or a prop mechanism in it that might be "off" (using the block off the 1974 would've solved that).

Also if the master cylinder is "remanufactured" it's a crap shoot, I've had to exchange disk brake master cylinders in the past for "soft pedal" out of the box, due to bad fitting of gaskets, bad repacking, in one case, I fixed the problem by swapping the "lid" off the old master cylinder...

good luck,

-D.Idiot

The drum prop valve you talk of is not a prop valve. It is only a switch that turns the light on your dash if either the front or rear brake system looses hydrolic pressure. You need either the prop valve off the donor car or the adjustable you mentioned in conjunction with the switch. This may also be leading to your problem.

As Eric mentioned an all drum car doesn't use a prop valve, it's a splitter with a warning light switch built in, nothing more. An aftermarket prop valve is ok to use under two MANDATORY conditions, first that you already have a factory style disc brake COMBINATION valve, which is what most people wrongly call a prop valve, AND your rear brakes lock up before your fronts. If both conditions aren't met you are wasting your time.

An aftermarket prop valve merely adjusts the rate of pressure increase, nothng more. A factory combination valve performs that function and also addresses the huinge point and holdoff functions, both of which are mandatory for proper disc/drum braking functions.

Unless your rear brakes lock up before the fronts then an adjustable prop valve will only decrease rear brake function. A better method for the A body anyway, might be to buy a smaller rear wheel cylinder, especially if you need new ones anyway. That usually fixes any rear wheel lock up isse without having to resort to splicing in an adjustable prop valve.

Steve