26 After a decent amount of break-in miles on the street, we strapped her back down on our Dynojet. Ready to go, we nailed the throttle and were rewarded with a higher peak output of 311 hp at 5,000 rpm and higher peak torque of 344 lb-ft at 3,500 rpm. We knew the engine was running rich (which can hurt power output), and noticed that the air/fuel ratio leaned out to the high 12s, low 13s with the head swap. Since the only parts changed affecting hp numbers were the heads, we know for a fact that these heads are worth 30 hp straight up on a low-compression big-block. And with better-flowing heads capable of more lift (max lift for our heads is 0.700 inch), the number of cams we can select from in our next performance upgrade is greatly expanded.