Does the proportioning valve on a 1973 F150 have a residual pressure valve built into it to keep some pressure on the front calipers.

 

I don't know they answer to your question, but I know you'll get more replies if you edit your thread title

 

No.

RPVs were originally installed in the MC ports that supplied pressure to the drum brake circuit(s). An RPV would not have been jnstalled in a MC port that supplied pressure to a disc brake circuit.

If your MC is a parts store replacement, there's a really good chance it will not have an RPV in the secondary port, even if the OEM MC did.

Diagram of a manual drum/drum MC.




But, the factory disc/drum brake valve for your truck will have a metering (hold-off) valve in the disc brake circuit.

 

No F150's until 1975.