The most expensive Impala is the 1963 Z11 lightweight with 427/430-hp engine, which has an average #2 (Excellent) value ofR$367,000. The 427-cu-in W-series engine doesn't have much in common with the splayed-valve big-blocks we'd see beginning in 1965, other than its bore spacing.
On average, you should try to stay away from used Chevy Impalas that were built before 2013. Indeed, the ninth generation Impala's first three years of production from 2006-2008 were the least reliable years of this vehicle. However, other less reliable model years of the Chevrolet Impala include: 2009 Chevrolet Impala.