WHO WINS? FULL AIRFLOW & DYNO RESULTS-ULTIMATE LS HEAD TEST. 11 SETS OF LS CATHEDRAL HEADS. How much hp can stock LS1 heads make? Do ported stock heads make as much as after market heads? We tested more than a dozen sets, but this video included the best 11 heads. We measured port and chamber volumes, airflow in cfm from .050-.700 lift and then HP & Tq on the dyno. Full specs, airflow and power are supplied in detail.