FULL DYNO RESULTS ON 1971 BOSS 351 AND 1965 HiPo/SHELBY 289. I n this video, I compare my most and least favorite Muscle car SBF motors. The 1971 Boss 351 was the most powerful factory small block ever made, while the HiPo 289 was the most disappointing to me! I think a good 1988 5.0L LX would walk it! Tell me why I'm wrong about the little 289!