Stopping Power

[wxman1]

I've got a 1969 C/10 1/2 ton P/U. From what I've
read disc brakes were not an option until
1971. The truck has drums all the way around. However, the truck has the large disc brake master cylinder and the proportioning
valve. At first I thought that this was the brake
warning failure switch, but it looks more like a
proportioning valve. So, the only thing I can
conclude is that one of the previous owners
put a circa 1971-72 booster-master
cylinder-proportioning valve on it, possibly
from a junkyard.

This is the first vehicle that I've driven in a
long time that had drums all the way around.
While the drums will stop the truck, I can't
lock up the brakes. Some would argue that's
a good thing. At any rate they just don't stop
the truck as fast as I would like or as fast as I
think they should.

Well, at any rate, I replaced the booster and
master cylinder with like kinds. I also replace
the front drums. The brakes have been bled
all around and the peddle is firm, not spongy
at all.

So the only component left is the
proportioning valve. Does anybody know how
to adjust this thing in order to get more
braking up front?? Pix included at URL below.

Proportioning Valve