Size and efficiency are not synonomous; by your truck motor example I can assume you obviously understand that a larger heat echanger has greater potential for cooling, so hopefully I can help you understand that hotter oil also has more potential for cooling. Think about this second grade science experiment, take two ice trays, fill one with hot water and one with cold water, put them both in the freezer at the same time and see which one feezes first. Right, the one filled with hot water because it has greater potential for thermal transfer. The following values are only for the purpose of explanation; 200F oil passing through a given cooler may shed 10F, while 300F oil passing through the same cooler may shed 20F, either way whatever the cooler sheds is removed from the overall oil system, so would you rather remove 10F or 20F. You're right, It wont cool the 300F oil to a lower total value than what it cools the 200F oil, but more total heat will be removed from the hotter oil. Okiephillip tapped his oil system at the hottest possible point, if he changed his crashbar oil supply connection to a sandwich type filter adapter, his system would not cool as well as it does right now. Most folks, myself included, tend to rationalize Harley oil cooling based automotive water cooling conventional wisdom just because it is familiar territory, but the way oil and water cooling systems perform is very different. I will agree that increased oil volume and time outside the heat cycle greatly contribute to the effectiveness of the crashbar cooler. You are also correct in all the other changes to Twin Cams that contribute to higher temperatures, but the most significant factor from a cooling standpoint is the position of the filter within the system. My comparison to Twin Cams and predecessor motors was to show the difference in the design of the oil systems, and attempt to explain why the Twin Cam is less efficient at shedding heat in stock configuration.

 

That's friggin' awesome. Nice job