[JoeC]

From what I read, it was Roger Penske who worked with Chevy to make some Aluminum small blocks while he was employed at Alcola Aluminum, CO. in early 60s. They were used in the Grand Sport and Hall's Chaperals. When the BB Chevy was released Hall used the alum BB based on the 4.250 bore 427. This ZL1 block proved to be a weak design and did not hold up to rigors of 8000rpm CanAm racing. So Chevy did a new block with 4.440 bore which looked similar to the ZL1 but was stronger using a siamese cylinder design. The ZL1 blocked was used in road racing Corvettes because the Can Am block was illegal and the ZL1 did well where RPM was not as high. The top drag racers used the CanAm block for match racing in 69 and in Pro Stock starting in 1970. The CanAm BB Chevy alu engine went on to dominated CamAm racing beating all contenders including Ford, Porsche and Ferrari until Porsche went crazy and built the duel turbo 1100hp cars. This CanAm block was also used by Bill "Grumpy" Jenkins to win the first ever Pro Stock race in Pomona 1970. Don Yenko raced a ZL1 powered 1969 Camaro at Daytona or Sebring. I asked a ex-Yenko race machanic about this and he confirmed it. He said it was very fast and stayed with the top Corvettes but Don blew it up. He said he still has some of the mangled valves from it.