I am looking into overclocking my 8320 and need recommendations for heatsinks that will provide a good overclock and temps. I don't have a lot of room for the largest collers so a mid range and sized one should fit. I am using an ASRock 970 pro Mobo.
I wouldn't try overclocking the 8320 on a 970 chipset motherboard. You should get a 990 chipset instead. But to answer your question, a Cooler Master Hyper 212 EVO and a Notuca DH-N14 would be a good option.
I've got my 8320 overclocked to 4.4ghz with 1.425 volts on a GIGABYTE GA-970A-D3P motherboard with a Corsair H100i cooling it. Not sure if I should be using a 970 motherboard for this but I'll take the fact that it hasn't exploded yet as a sign of success. H100i, if you can afford it, is an excellent cooler since my cpu stays below 30 degrees at all times.
I'm in the Bay Area and it's been between 50 and 60 degrees Fahrenheit lately and around 30 in the morning so that has definitely had an impact but I built my system in September when temperatures were around 70 and 80 degrees Fahrenheit and it still did an excellent job cooling then. At stock speeds I think it still stayed under 30 Celsius while gaming. I don't know how it'll perform while overclocked over the summer but I doubt that I'll have any problems with heat. My case might also have something to do with the temperatures since I've got an Arc Midi R2 with the H100i as an intake in the front of the case with another 120mm fan as an intake in the bottom of the case and 3 140mm fans as exhaust in the top and rear of the case. Obviously, results will vary.
You don't really need an expensive cooler to get to 4Ghz. It really depends on how much overclocking you want to do. The H100i is a great cpu cooler but unless you want to really push your cpu, getting an H100i would just be overkill. If you only want to get to 4ghz, then you should just look into getting a good air cooler. You'll still be able to get the overclock you want and save quite a bit of money since the H100i is going to set you back around $100. It would also be a good idea for you to read reviews on your motherboard though and see if it will support overclocking on your cpu. You might want to consider upgrading to a motherboard with the 990fx chipset since those motherboards are better for overclocking.
I have my 8320 at 4.2GHz on a MSI 990FXA-GD80 V2. The heat sink I use is a Thermaltake Frio. With prime95 running all night max temps hit were 48C with average being 45C. Honestly though, I'm in a slightly warm room and it usually idles at 33C when I'm light using it. Under gaming it'll hit 41-42C. I might also have a bit of a good chip since I've not even touched the voltage yet and it hasn't ever given me an issue.