drag brakes plumbing
So, trying to figure out what you're doing. You're adding a proportioning valve like this...
in order to control the front/rear bias correct?
And you want to know if you still need the stock combination valve?
If that is the case, I see a couple reasons to keep the stock combo valve. One, you still need to split the lines to the front brakes somehow. Two, assuming you still have drum brakes in the back, you need a residual pressure valve. That valve resides in the stock combination valve . Finally, I'm guessing that since this is a race car you're not worried about the brake lights, since one of the switches is also in the combo valve.
If all that is right, then you can ditch the stock combo valve as long as you use a brake tee to split your front lines, and plumb in a residual valve for your rear drums (10 psi for drums, 2 psi for disks). Personally, I'd keep the stock combo valve as long as its working properly and just add the proportioning valve for the rear. Or you could use something like this
Which solves your distribution block and prop valve problems, and still leaves a switch for the brake lights if you ever need them. You do still need a residual valve if you use rear drums with this one, found that one out the hard way.
So, trying to figure out what you're doing. You're adding a proportioning valve like this...
in order to control the front/rear bias correct?
And you want to know if you still need the stock combination valve?
If that is the case, I see a couple reasons to keep the stock combo valve. One, you still need to split the lines to the front brakes somehow. Two, assuming you still have drum brakes in the back, you need a residual pressure valve. That valve resides in the stock combination valve . Finally, I'm guessing that since this is a race car you're not worried about the brake lights, since one of the switches is also in the combo valve.
If all that is right, then you can ditch the stock combo valve as long as you use a brake tee to split your front lines, and plumb in a residual valve for your rear drums (10 psi for drums, 2 psi for disks). Personally, I'd keep the stock combo valve as long as its working properly and just add the proportioning valve for the rear. Or you could use something like this
Which solves your distribution block and prop valve problems, and still leaves a switch for the brake lights if you ever need them. You do still need a residual valve if you use rear drums with this one, found that one out the hard way.