Dave- Give it Chicken to pinch and replace the front bearing if you haven't done so already. Check rod for wear and let it rip. It sounds like the compression gets low when hot which would indicate a need for a pinch. It's worth it for you to pinch and replace the bearing. Engines are made from different grades of metals and the fact Chicken's Plus 4 has half the compression and runs good is the simple fact that the brass and chrome lining are different from the OS. The OS sleeves expand more than most under heat and pressure because of a different grade of brass and chrome and that is what you are experiencing when the engine comes to temp. I have had several Novas with over 5 gallons each and all have enough mechanical pinch to push the sleeve out of the block cold and oiled. I know you guys never preheat your engines before running them and that is the quickest way to send them to the grave. Some guys snicker at the engine heaters I have but when they last into the 10-12 gallon range with no problems and original pinch and it is the only engine I run all season. I am the one snickering at the guys who buy 3 engines in one summer just to make it by or the guy that has 6 engines and none of them run decent. It's an investment to have and use the heaters and I have a bunch in stock if you want any. Not trying to discourage you, just trying to point you in the right direction. See you at the next race buddy!