hgerhardt on the right path here. Set an angle value cylinder next to a parallel value cylinder and you will not beleive the difference in the number of cooling fins, more on the angle value cylinder. More area more heat is disapated, simple. The piston cooling nozzles are for, well, cooling the pistons
. That heat has to go somewhere right, like maybe into the oil.
I'm running an angle value 320 and it's a kick *** little engine. Lycoming should of made one. Great fuel economy and power out the wasszoo on the top end, just will not pull with the 360's down low in the rpm's.