Is brake fluid pressure the same for all four wheels???

[Bartenfeld]

As far as I know there are no proportioning valves on a 1966 pickup. This tells me that equal amounts of brake fluid pressure are going to each wheel cylinder. Am I right or wrong?

[scottofksu]

No, it differs front to back. Your proportioning valve lowers the pressure to the rear.
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[scottofksu]

That's what I get for not reading the entire post... I believe the line to the rear is larger and, absent the prop valve, this reduces the pressure in addition to the front brakes being the first ones off of the master cylinder.
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[Heater63]

I have always been told the size of the line does not vary the pressure. If you have drums all around, each wheel cylinder sees the same pressure, irregardless of line diameter.

The proportioning valve is added when you have disc/drum systems, as disc's need significantly more pressure. The valve reduces the pressure going to the drums in the (typically) rear. You adjust it using a gauge, OR by increasing pressure until the rear drums lock up in a hard braking, then backing the pressure back down till they no longer lock the rear brakes.

[jocko]

If your truck's braking system is still stock: factory 66 is single mc with no prop valve and all 1/4" line front and back - same pressure to all wheels.

To Heater's comment (which I agree with, but wanted to add to) - line diameter will affect pedal effort to produce the same pressure signal. In 67 (and later) drum/drum dual reservoir master cylinders, the internal piston on the mc serves as a poor-man's prop valve (there was no external prop valve - the thing you see on some of them is a brake pressure transducer) because when you press the brake pedal, it allows pressurized fluid to engage front/rear in slight sequence by way of when the front/rear ports are uncovered when the piston slides forward. But once both ports are uncovered, equal pressure to all 4 corners.