Crow,
To answer your question and not ridicule your wording, your bow manufacturer sets a minimum arrow weight to 5grains of arrow weight for every pound of draw weight ie. a 70# bow should not have a arrow weight of less than 350gr. That is the lightest arrow they recommend and also they will void warranty if you use anything lighter. As for KE the common denominator generally used is anything over 45#'s of KE will harvest most north american game. However, if you are using a large cutting dia. mechanical that number does not apply, you would need to be in the 60#+ range IMO, If you use a COC Bh then it would apply. Like I stated earlier and as Robin stated, I try to tweak mine to gain the best combination of speed and KE....Also as Robin stated a KE of 80+ is not very common but with some bows is achievable. Most of my set up's over the last10-12 years have produced 70#'s+/- of KE (which I feel is necessary with the BH I use)and that has proven to work well for ME and my set up.I hear a lot of guys on here talking of an animal running offwith an arrowstill in itand personally I have never had this happen, I have found all my arrows on the other side of the animal after passing completely through them. To some that may not be important but I put ahigh emphasis on thatwith my set up's. Which is why I try to get the best combination with my set up's every time.