I have hardened valve spring shims that I would like to use on stock 340 heads and springs. I know to put them on the Head side, not the retainer side. My question is, has anyone ever had these shims get pounded out over time, buy the spring? Thanks.

Every shim I buy for every head is a hardened shim. I refuse to use the cheapies. Any shim will wear over time but the hardened ones hold up well

i have used standard shims mixed with the tool steel shims and I make sure the harden tool steel, spring steel shims, are installed next to the springs

the main issue it that the shim fits snuggly on the valve guide boss, so they don't slide around. I have never seen one fail if it fits the guide boss correctly. I use common spring shims made for engines that have one side with ridges, that helps them from rotating on the spring pad. Available at any source for engine parts. I buy a lot from Goodson tools.

Depending on what you have and trying to accomplish, in some cases you can make adjustments to spring installed height & pressures using +.050" or -.050" locks and/or retainers.