I am building a combination 70/73 240Z ( I'm using the '73 body ) . I am using the front mounted proportioning valve from the '73, but can't figure exactly how it is mounted. I know it has two holes in it, but apparently only uses one bolt. Does the other hole index on anything, to keep it straight and secure? Anyone have a good pic?

...Zs had a proportioning valve. Are you talking about the safety switch in the circuit that makes the brake light come on if you lose front or rear brake pressure?

Bruce, the pressure isn't regulated between the front disc brakes and the rear drum brakes? Of course it is, and no I'm not talking about a pressure differential valve.

Here are a few drawings showing the location of the "Pressure Regulating Valve" and the "Dual Circuit Differential Pressure Switch" for the two different systems.

For the system with the PRV and the DCPDS located in the engine bay, Fig. 9.28. it appears that the PRV is mounted on the firewall, under the throttle linkage and adjacent the Brake Booster/Master Cylinder assembly.

It does look like it has two mounting holes doesn't it, but only one is used:ermm:

The DCPDS is mounted on the inner fender wall.

thanks . .so the other hole isn't used for anything? Nothing to index from and keep it from spinning? Even with lines attached to it? Seems like it would move as you attach lines.

That is an "known unknown" for me, to quote Ronald Dumsfeld.

Mine is a '73 also and doesn't have any mounting point at that location:rolleyes:

well that is right from the horse's mouth then, thanks!!

attached is a pic of my 73. hope this helps..

great pics Robin , thanks !! I may need other pics sometime if you don't mind. As you can see from my signature, I'm not a Datsun person. But I love these little cars and I'm putting togther a car that is in pieces )

can do, if i dont have the pic your needing im sure someone here will have one.