It's not really an "overclock" as you are not changing the clockrate of the memory but performance should definitely improve, although it's hard to say by how much. The increase will be so small though that you won't notice it on its own. But remember that many small tweaks will add up to a noticeable performance increase, so it may still be wort it.
If your system is unstable or won't boot after you've changed the settings, change them back as your memory doesn't support those timings at the clockrate you are running it.