"I left Ferrari at the end of 1969," Chris Amon said, "and always regretted it, but at the time it seemed like something I had to do. The cars always handled well, but the V12 sounded way more powerful than it was, and you could never convince the Italians of that.
"At Brands Hatch in 1968, for example, I started from the front row, and finished second after a long fight with Jo Siffert's Lotus. Mauro Forghieri and the others were annoyed I didn't win, but I was absolutely balls out the whole way. It was the same old story - out of the slow corners the Ferrari was simply blown off by the Cosworth.
"The following year was even worse, but we had the flat-12 coming for 1970, and I was impressed by it in testing. Trouble was, it kept breaking after only a few laps, and one day I just thought, 'I've had it - I've got to have a DFV.'"
Source : http://www.autosport.com/premium/feature/7636/the-greatest-engine-in-formula-1-history