13. 4.8L Stock vs. Modified Tested on the engine dyno, the stock 4.8L produced 333 hp at 5,400 rpm and 343 lb-ft of torque at 4,700 rpm. After replacing the stock components with a set of ported heads from Total Engine Airflow, a Crane 224/232 cam and FAST LSXRT intake, the peak power numbers jumped to 476 hp at 7,000 and 392 lb-ft at 5,900 rpm. The gains were most impressive at high rpm, but note that the modified combination lost no power to the stock one, even down at 3,000 rpm.