11 Graph 2: 350 Chevy— Stock vs. Upgrade 1 The first upgrade performed to the 350 was to replace the stock cam with what is commonly called an RV grind (Comp PE246-0.429/0.438 lift, 203/212 duration, and 110 LSA). To the cam swap we added a set of mildly ported 882 heads (2.02/1.6 valves) and a Performer RPM Air Gap and Demon 650 carb. The mild upgrades improved the power output substantially, and the power improved throughout the rev range. It goes to show what can be accomplished while retaining the stock heads. The PE246 cam is pretty mild for a 350.