Vintage Double Hose

I have several Da's in various states of restoration. I have noticed that several of the large heavy springs part @ 1000-40 are of varying height.

is ther a specific height for this spring. Dowes a shorter height one mean they are worn. I am thinking this because we measure valve springs on a piston aircraft engine to determine if they are within height spec. They seem to generate the same resistance, just differing heights. Any wisdom on this out there.

The spring is the controlling device the second stage IP. As the spring is compressed with the ajusting nut the spring pressure is always equal to the IP pressure. As long as the IP can be set without putting the spring into coil bind the spring is OK. There is no spec on spring free length that I have ever seen.

I agree with Tom. They are all over the board. I have never seen a broken one.... What I have seen many times is the spring with some type of red/brown grease on it, but I have never seen an service manual that says to do so ?