HI Art,

Nice pictures as usual!
You are my kind of man to tear something apart. I too, figure it can do one last thing for me, before its gets tossed. It's these cheap lessons that give me my two cents worth of knowledge. (:-)

I have never torn one of these up to peek inside. I think I had one on my '84 fail to hold rest pressure overnight. It seemed to help stop or change long cranks but the car ran fine and started better? I'm not one to tear something up without lots of proof to make it bad. I may still have it around...? Waiting, for the desperation of the someday of having nothing else to do!

I have talked about how they work and have only imagined how I would build one to do what it does.
In my minds eye, I would think there must be an way to adjust a spring against the force of another spring or force to get precise results.
With that said, did you notice a way to adjust the vacuum side spring through the port. This would set a amount of flow plus or minus of the other preset spring pressure on the check ball itself.
Something like a screw to push on a base plate under the large spring.

If nothing else they could use shims but these would have to be preset in a fixture of the same length as the cavity between the two halves of sheet metal bulbs.
Maybe they test it just before they put the final rolling crimp on the rims. $39 to $100 pays for things to be done by hand the old way.
Crimping helps stop repairs or allowing a refurbished market to appear. That is, until the price gets too high and someone else says "I can do that for less!"

Looking at your photos it seems that the ball and seat are frozen together while it was down inside between the cases. That would explain the 100 PSI. That tiny spring is like a fail safe if they locked together. I'm guessing something chemically bonded that shouldn't have.

It looks like you ground down the outsides to split them apart.
Looks like to got some of the sealing ring that holds the diaphragm suspended. The sides of red rubber are like our thermostats as it gives more to crush and seals the edges.

In the next picture it looks like a tip of a soldering iron showing.
It also looks like you had just started to separate the inner piece, with the slotted plate, from the diaphragms larger support plate.
The support plate was made to work with the larger diameter spring to give it a place to push.
It looks to me that this assembly was riveted together with the rubber diaphragm in between.

I'm with you in understanding that it looks like a pocket, for that spring you found. It also could be the inner diameter of an orbital rivet and still it looks convenient pocket for the spring.

The slotted plate looks to be made to allow the ball to enter from either side as the ends could be bigger than the ball.
If you wanted to drop in a spring, push it down a little with a thin flat tool, push or slide the ball in from either side and load the spring with the ball on top. The center cutout would be made with a smaller cutout that holds the ball in place.

If it was not assembled this way, COLD, it could be just stacked and then soldered? The riveting has to come later.
From the depths allowed out from the cone depth I do not see the first assembly method working and it would explain the solder ridge. The orbital riveting is still done on the back plate side.
The openings on each end on the sides of the ball are still there to allow gasoline around the ball.

I cannot tell from the pictures how the seat itself was held in place to the gasoline side of the case.
It looks like the seat came apart with the steel ball attached with the halves first opened. The seat in one picture looks black on the outlet side. It looks to me like a machined angle seat with an orifice hole when looking straight on to it.

Another picture shows the ball is turned upwards with something.... A looking silver plated attached.
This might tells me the ball was under the slotted plate when unsoldered. The seat looks cocked on the ball with the solder gun ready. The spring has rotated the ball and the seat attached or the ball was just loose without the spring and it took up all the play available to one side?

I have seen spring loaded seats with preset check balls in hydraulics. Most working with offsetting pressures temporarily to change flow directions to other ports. Some people call them spools and proportional controllers. Solenoids and poppets used with variable ports containing slots or vanes in their outlets. Tricky engineering compared to FPR's. These are simple devices since they control only one thing.

Can or did you see the seat side and how the seat body sit upon or in the fuel side chamber?
Was there another seal or holder within the outlet chamber to hold the seat body in place?
This is my mystery question.
How did they seal that outer body of the seat on the fuel side outlet? I'm missing a detail.

Is my day coming to see if I kept that old regulator?
(:-)

Phil