By David Major
I set out on this adventure due to the fact that all-drum brake systems now days have to many problems due to the decline of quality brake shoes. I just could never get the "pulling" ,left then right, out of the brakes no matter how many "adjustments" I made.
I wanted to maintain maximum stopping power so I went with the dual piston set-up.
I purchased from the "donor" truck in a Pick-a-part the caliper bracket’s, prop valve,
1.Jack up vehicle, set jack stands
When I comes to the brake line’s ..I reused the one that goes to the right front,
One thing I learned about double flaring, it takes practice and lot’s of it. You will not be able to duplicate a "machined" flare! You’ll have to "play" around with the flare kit awhile to "know" what the best placement is for the line in the tool will be. I started off with some "ugly" bent double flares till I "learned" the right time to STOP the squeeze down with the adapter. I practiced with new line,(so I threw away 3 buck’s). This is the most important and serious thing that you will do! They cannot leak. (After I was done with the project I checked those line connections for a week!)
Get all the "ends" you can when you get the proportioning valve you’ll need them. They are all different sizes. You might have to search for a valve that doesn’t leak. I even got one from an 83′ van, never did find out if they are different in operation but it will have to be one for dual piston calipers.
One important note!!!!!! Make sure you KNOW which line goes from the right front into the prop valve and the left front into the prop valve, it makes a difference! Just as the lines from the master cylinder.
To install the two lines from the couplers (near the frame up front) to the propvalve you can use pretty straight line (except the easy curves at the ends) I secured those lines by using a short piece of vacuum line so they don’t rub on the frame holes while going to the prop-valve. The left front brake line was easy,(nice a short). I also used the original mount for the flexible brake line to the calipers. (Although the flex hoses are kinda long)
Once I got all the line’s hooked up to all the wheel’s , the master cyl, and the prop-valve, I used a strip of steel, bent it to bolt into the frame and then the prop-valve.
Your next step is the bleeding part. Of course I bleed the Master cyl first without the lines hooked up. Then it’s that slow process of getting the fluid to all the caliper’s . I sped everything up by using a Mity-Vac. It really help’s getting rid of all the air. I did finish the job by doing the Ol’ "pump" them up and hold it routine. You might hear about "pulling " out and holding the bleed rod in the prop-valve but I Didn’t and it bled fine.
I was really surprised by the straight path I took once I "got" on the binders. I stopped straight with no wandering. You will have to wait for good stopping power because of break-in of the pads to the rotor’s.
You now have a Van as good as a ’75 or better!