Before doing anything list your parts so you can avoid issues all of them including case fans if you have any
Here is what I would do. Get decent cooling 2 case fans at least tops 4 with one intake rest exoust depending of case ofc.
Next will be undervolting your cpu yes undervolting to reduce vcore or it will spike out and cause extra heat that you don't need, keep in mind that you have turn off all
power saving fetures, also set multiplier to default clock disable turbo when doing such things go one minus at the time and use IntelBurn test to check for stability also something like
HWInfo for temps. I could run at 3.5 on 1.220 instead of default 1.340.
When you find your min voltage start with increasing multiplier, when you get crash of any sort, BSOD error on INtelBurn increase vcore by one and start test again, keep going untill your temps are at range that you want, I think for 8 core are around 62c not sure check that out. Also if you notice huge climbs or drops in vcore or speed (200mhz or more less then 100 is fine) use LLC try with each setting of it, I think Medium should be fine. Idk have I forgotten anything Remember when increasing multiplier your system must be stable, also when increasing anything go ba one + not more.