 The Callaway HH Indy Car Engine was a project to build a racing engine for IndyCar specification from semi-scratch as an eleven months long program between 1980 and '81, to show Callaway's capability to design and implement complex high performance engine program.The "HH" design engineer was famed BMW and now freelance engine designer, Hans Hermann.The HH Indy Car engine V8 block was designed to fit two Hermann designed, Drake Engineering water-cooled Volkswagen 16-valve cylinder heads.