No. But yes. But no.
There's a couple factors behind the answer. It's a deceptively complicated question

1. The Overclock spell does not increase the Rating of a device, only the Device Rating. It's kind of messed up, but those are two seperate things

2. On the other hand, the Jammer rules (pg. 270) do make a mention that their Device Rating equals their Rating, so on THIS device, yes, it works!
3. But later on, the rules also say that the max rating is 6. So, no, you can't go to 8. If you had a Rating 4 Jammer however, yes 2 net hits on Overclock would turn it into a Rating 6 Jammer as long as the spell was sustained.