8 hours ago, Zed Head said:

CO mentioned valving.  I looked around and found a mention of residual pressure valves.

Yup. We got into some of that in those threads I posted:
https://www.classiczcars.com/forums/topic/66276-brakes-dragging/?&page=2
https://www.classiczcars.com/forums/topic/66168-brake-master-cylinder-identification/

 

On 1/24/2023 at 7:45 AM, Captain Obvious said:

I don't have pics of the older style of master cylinder exploded, but this is what the later one (with the front circuit closest to the firewall) looks like:

Here are a couple other threads with pics and significant discussion about master cylinder operation:
https://www.classiczcars.com/forums/topic/66276-brakes-dragging/?&page=2
https://www.classiczcars.com/forums/topic/66168-brake-master-cylinder-identification/

 

Helps to pull out the specifics.  But, it's out there now.

Still don't know what Nissan used though.  It was the early days of disc brakes.  Surprised that they did not mention it in the FSM if it was there and important, but did mention the volume of the reservoir.  Those early FSM's are like text books, very thorough.  Every component explained in detail.  Test bench anybody?  I don't have any parts or a garage to work in right now.  Maybe later.

If the MC does maintain residual pressure then opening a rear bleed valve should get a small squirt.  Not sure exactly how the proportioning valve will affect the end pressure but it looks like there should be some maintained (want to go back to math class - read the description of the proportioning valve).

Anyway, there's a lot out there but still not clear what's what in the end.  Can't go wrong with F and R though.

11 hours ago, Zed Head said:

want to go back to math class - read the description of the proportioning valve

Haha! Like this: