Too big a cam mostly. I ran a high compression 273 4 speed, while my brother ran a 2 barrel 273 Auto converted to 4 barrel. He ran the stock Commando cam, while I went bigger. His car was quick, would cruise at 100 mph all day long and had a top end of 140 mph. In their best configuration, they were both running small TQ carbs. At one point near the end of daily driver status, he had me swap to open chambered 675 heads so he could run regular gas.