I checked brew pressure on my 2004 Rancilio S24 by ULKA pump OPV overflow/bypass
27cc/30 sec = 54cc/min which correlates to 12-15 bar median/avg ~13.5 by their chart.
I have seen Silvia adjustments, but was wondering if anyone had tips on how this one is tweaked?
Looks like I would need copper gasket/spacer rings.
Thanks

I think you're correct... A picture with the OPV open would be more trustworthy. It is possible that the threaded barrel in there actually has an adjustable insert under that cap, like in the old Cuadra machines.

If it is hard to adjust, don't force it, soak it in descaler, heat it (If you don't suspect rubber/plastic valveface), then gently force it, otherwise you'll just tear the brass to bits.

Actually screw the above ideas... It's got tonnes of room, plenty of space, nice flexible braided hose connection.

If it gives you a hard time, laugh at it and replace it with a better OPV.

Is it even adjustable, replaceable or can one add a second one inline?
Looks like I would possibly need copper gasket/spacer rings if it is adjustable

Here is a catalog picture of the same valve , on a pump

I don't know if it's adjustable or not. I would if you provided a picture of what's in it, but that's been said. Everything's replaceable.
It certainly looks too short to have much of a spring in it, so I will bet it's NOT adjustable beyond the possibility of different thicknesses of copper washers. You have it, I think, in your machine. Go ahead and see.

You could just use a modern Silvia OPV :

https://www.espressoplanet.com/coffee-a ... Valve.html

You could replace whatever that "From Pump" hose is with a decent braided hose, the Silvia one if it's the right length, perhaps.
https://www.espressoplanet.com/Rancilio ... -hose.html

Transfer that outlet(Boiler side) fitting 1/8 to 3/8 or whatever it is, and you've got an adjustable OPV.

This is assuming that the other end of that "From Pump" hose is connected to a 1/8BSP Male elbow. If not, fittings exist, your job to do some of the figuring out

My assumption, without taking it apart, is that it is like this OPV:
https://www.espressoparts.com/products/ ... connection
Same as used on old S20/Epocas, or early Silvias.
There is an Epoca manual that shows the internals on page 23:
http://www.jeoushun.com/rancilio/EPOCA-DE_Manual.pdf
and , as you say, the new Silvia OPV might well bolt in.
It looks as if the S24 OPV it is not adjustable, but can be kludged like the V1 Silvia as seen in :
Rancilio Silvia v1 - Pressure drop problem

Otherwise, the only adjustment is either by swapping internal springs or spacers, neither is easy to find.

Apparently, Early OPV's were just commonly set by the factory and not adjustable, that being a newer fashion
with brew pressure adjusted by puck and luck, at the portafilter level.

I am assuming the threads on the Ulka output is 1/8"BSP, and am searching that. (FOUND confirmed)
Rancilio seems to like bolting the OPV's to their input or output, on the tapered threads. (size? of output. prolly 1/4 BSP)
.
Thanks for the Canadian parts site, it supplements Espresso Parts, down here.
I'm trying to detail the parts , adapters, thread sizes etc before tearing into it, BSP fittings ain't at my Home Depot
$70-80 and some hours just to be able adjust the OPV is a bit much, and that's before I break anything.
Though the pressure I'm getting (~13bar by flow) is pretty high and my shots are getting way too much flow,
despite grind and tamp changes.
I need to get a portafilter gauge to verify and follow the Ulka flow pressures.
and try some other coffees, to play with the variables , before tearing into it.
Fortunately the S24 is as easy to work on as an old Chevy.
Thanks again