3.75 stroke. What is the bore size (Im thinking 4.12inch to get 400ci)? I have a XE284H cam in a 10.6:1 360 and it runs fine on 91. As I stated above great cam. W a 5.565 rod, 3.75 stroke, and 4.12 bore I came up w 8.47:1 dynamic and 171 cranking pressure. 8.5:1 is about the highest you would want to go on pump gas w/ iron heads, so you will be fine. Im worried about one of my engines. A aluminum headed .030 over 340 w a custom ground Comp cam. Static is 10.5:1 cam is 54 ABCD putting my dynamic @ 8.9:1 w 185 cranking pressure w a nice tight .35 quench. The short stroke is helping my cylinder pressure and Im going to give her a shot and see if it will run fine on 91.