To be honest i don't think it'd be a heating problem, usually if a computer gets too hot it will shut itself down to avoid and permanent damage, however you could try using some past between the heatsink, it's not much and for what you'd gain or loose it's probably worth it.
I don't know enough about dual core processors or your type of mobo, but there's a little battery on there that keeps all the clocks in sync usually, it might even be worth taking that out, or replacing it for the amount it would cost you