This is a long shot. But I have been amazed before with the knowledge base here.

The 1972 with 2.0, increased to 2.3 liter, engine has had some other modifications done to it, besides the cylinder size increase. one of those mods is the size of the springs that pull the valves back into their seats.

We now find that one of these springs is broken. The Previous Owner will not (or cannot) tell me what size spring this is (or what kind of car it came from). The repair shop owner has not yet been able to identify this either (not from 944 or 911 models).

Please see picture and give it your best guess.
Thanks so much for participating.
Click to view attachment

Repair shop should know how to measure springs*, then look in appropriate catalog.

*free length, ID, OD and pounds per inch compressed.

Someone welded the perches to capture a smaller OD spring.
My bet is they're aftermarket VW type one dual springs, maybe even the Chevy "style" (not really Chevy) T1 drag racing springs.

Are they a dual spring? inner and outer.
what size are the valve stems?

Interesting work done on that head.....Len Hoffman might know....

Mark,
The springs are a single coil.
Not sure about stem-size (car is not at my home).

Thanks for responding.

They look like the commonly available CB springs and retainers.

Not sure why the perches were welded. The singles drop in and fit perfectly with no mods. Perhaps the heads were previously machined for duals and converted back.

My 1.7 has springs that are thicker than stock. No idea why, was planning to sort that out when I get the body done and start on the top end.

Could be using just the outer spring of the chevy style spring, only way to see is to remove the springs and test how many pounds the springs are.
There again the springs could be out of anything, you can buy all different types and sizes of springs.
Hans get your machinist to remove the springs, measure the stems and springs and post some pics of the work done to the spring perches.
Also if it is 8mm stems the valves should be oversize, get him to measure that as well.

They are indeed the Chevy style springs.
When we took that first picture we did not notice the inner spring.
At the moment the engine is out the car again and the heads are off.

We are installing new springs.

Valve size is:
Intake 44.35 mm
Exhaust: 38 mm
Cylinders are 103.8 mm

(See new threat about cylinder condition)

Thanks for the input you all provided.