i put the merlin oval on my chevelle 427 and it runs 11.70 all day with a comp cam hyd. on the dyno it put down 416hp and 467 lbs. this is out of the box with 230 valves and all brand new parts you cant go wrong. if your spinnig under 6,000 rpm. the rectangle are the same price and will make more power 3800 to 7000rpm