Anybody know the serviceable length for valve springs

If you are looking for a dimension of assembled height like a modern engine would have, I don't think that number was ever documented. "It is what it is"

Oiling of the cam shaft lobes was somewhat limited on these old engines, so it is not a good idea to get too carried away with the valve spring tension. You should be able to push down and exercise every one of the valves while assembled on the cylinder head by hand.

Hi smlogan

I'm sure I've seen this information in a service publication somewhere, but can't seem to find it.

What I have found is that in the 1929-54 Master Parts book,
it lists the same valve spring for all 1929-33 engines,
and shows it as being 2-1/16 inches free length when new.

And 31/32 of an inch in diameter.

The springs will likely lose a little length over time, and I'm not sure how much would be considered allowable to still be serviceable.
If yours are anywhere near 2 inches, I wouldn't be concerned.

Additional information: The spring pressures for both the intake and exhaust valves are 45 Lbs. valves closed and 80 Lbs. valves open.