Proportioning Valve Question...

[fiftee6]

Hey all, just finishing up my project and need to install my Master Cylider. My question is, I am using a dual booster, corvette style master and a standard proportioning block on the left side.

Do I need to use a 10LB check in the rear drum line, and or the 2lb in the front???

I am running a disc/drum setup. When using the proportioning valve, is this 10lb gizmo omitted? Thanks in advance...Phil

[Rick_L]

If you are using the GM/AC-Delco combination valve for disc/drum that most places sell, it has a residual valve in the rear port. No need for an additional one.

You don't need a residual valve in a disc brake line unless the m/c is lower than the caliper.

[twolaneblacktop]

I have disc brake conversion up front with drums in the back, a manual master cylinder of a 76' ford granada that also had disc/drum setup with no porpitioning valves!! And the car stops great!! Is this common or did I just get lucky??? The car is mini tubbed and a friend told me this help because it takes more force to lock up the wider tires and make them slide???? Does that make sense or did I really get Lucky?!? I'll take luck with this car every chance I can get!!

[Rick_L]

Think about it a bit. The cars which the proportioning valves are taken from were 70s cars that weighed about the same as our 55-57s and the valve was designed for having the same size tire all around. That would mean that the prop valve would need to cut pressure to the rear brakes under maximum braking force (the rears would lock up first).

Now, you've put a little tire on the front and big tire on the rear. You've decreased the traction on the front and increased it on the rear. This does mean you can you more brakes on the rear than the front.

BUT, you are not lucky! Your car doesn't stop as well as it could.

[MikeKy55]

Another consideration is without the valve, if a line burst front or rear, you will have NO brakes. The valve also serves to shut off which ever end of the car has a problem allowing the other end to still stop the car.