Throughout the 1960s, Ferrari's focus on Formula 1 slipped as money grew tighter and engineering resources were increasingly directed towards sportscar racing and Le Mans. This was, after all, a fertile ground for selling cars to customers and a rare European playground for American interests. Enzo had famously come close to selling out to Ford before ultimately reaching terms with the Fiat empire to sell a 40% share of his business.
The upshot was that Ferrari's first car for the three-litre era, the 312, was overweight and underpowered, having inherited its engine from a sportscar. Frustrated by both this and the annual failure to get any meaningful F1 development work done until after Le Mans, John Surtees left after a bust-up with the team in 1966. Successive iterations of the 312 failed to deliver the goods on track as the powerful, flexible Ford-bankrolled Cosworth V8 became ubiquitous.
The 312 (three litres, 12 cylinders) designation served Ferrari for 14 years and covered many cars, including four carrying the B designation (one of which would never race). During the service life of the B models, Ferrari's very commitment to F1 would come under threat.