The 1969 ZL-1 Corvette came equipped with an entirely new big-block engine option that produced more horsepower than any Corvette that had come before it. Any Corvette, when ordered with RPO ZL1, came fitted with an all-aluminum 427 C.I. engine that featured a dry-sump oil system and which weight approximately 100 pounds less than the L88 engine. The ZL1 was a mid-year release for the 1969 Corvette and was actually developed to replace the legendary L88. In addition to the all-aluminum block, the engine featured stouter connecting rods and open-chamber heads.
Actually when dyno’d with open headers the all aluminum ZL-1 427 produced about 530 HP at 6600 RPMs.. the all iron L-88 about 560 HP at 6600… aluminum bleeds off heat/HP faster than iron, hence the difference… of course, the all aluminum engine saved 100 lbs. in vehicle weight… helping to even up performance and yield better handling…
What is the source of your information? Read this, while paying special attention to the “How much real power” section. ZL-1 and L88 would be rated at some 376 HP under today’s (post 1971 model year) SAE net standards.http://www.camaros.org/copo.shtml