The heatsink is CM V8 (average heatsink) - my 1600 GHz RAM is running at 1485 (slight underclock) and is fine. Read the guide and set the RAM multiplier to its LOWEST number, and start your CPU overclocking.
5gb's of ram ? well thats part of the problem ... you should have all even sticks ex. i7 1366 motherboards have 6 memory slots, and you should be using all 2gb sticks, or all 1gb sticks ... They need to be the identical sticks for best performance. 1333 Mhz is not that great for overclocking because in my experience it kinda of limits you a bit. 1600 Mhz would have been a much better alternative But list your specs so we know what your working with....
pick a best answer ... and too get the best i would get 6x 2 gb sticks or get 3x 4gb on newegg.com and they are fairly decently priced right now and its an excellent time to buy ram .... if you have the extra money you could also go with 24 gb 2 x 12 gb kits .. 6 x 4gb and they have that for $320 ..... if your motherboard will support that much