Yet Another Proportioning Valve Question

[Coronutcase]

I see that some of you who have done front disc brake/rear drum conversions have installed your adjustable proportioning valve right at the master cylinder, coming off the front port (farthest from firewall) and then running the line that was in that same master cylinder port into the other side of the P valve. That line would then go down to the original distribution block where it always was. This is so much simpler (and makes sense) than what my directions say... It says to install after the original disribution block and tie into the rear brake line, and I've seen some of you do it that way too. It seems to me that it would work either way since the front port on the master cylinder only goes to the rear brakes.

So that's my question.... Will it work either way, or is one way better than the other.

Thanks in advance!

 

[Yatzee]

I think those instructions are a bit vague. A P valve usually goes directly after the port at the master dedicated to rear brakes and one line runs to the rear of the car and into the left/right distribution block which is usually mounted on the top of the axle tube. It is also a wise idea to put a 10 lb residual valve inline, directly after the P valve.

 

[Dragon Slayer]

The issue could be with the distribution block brake warning light depending on model. The pressure out the master cylinder ports is the same front and rear. That equal pressure at the distribution block keeps the plunger centered and the brake warning light off. If your already reducing pressure before the block, the warning light may activate. If no warning light probably doesn't matter.

 

[andyf]

Correct, all depends if you're doing a race car or a street car that has all the bells and whistles. If it is a newer car with a combination valve or a brake warning switch then you'll want to put the adjustable prop valve in the rear line after the switch. If it is an early car, or a race car with a stripped down system then you put the prop valve where you want it.