The 427 cubic-inch Ford V8s that won at Le Mans in 1966 and 1967 are among the most unlikely engines to ever run in the 24-hour classic. And they have a few secrets to tell.

It’s not clear who originated the term “lazy liters” to describe the strategy behind the Ford V8 that won at Le Mans two years in a row in 1966-67, but it’s an accurate one. While Ford’s chief rivals in those years, the Ferrari P3 and P4 prototypes, employed high-tech, high-strung V12s that revved past 8000 rpm, the Ford racing engine was closely based on the production Galaxie 427 V8 that anyone could buy straight off the showroom floor. And with 7 liters of displacement compared to the 4 liters of the Italian thoroughbreds, the big, lightly stressed Ford could loaf along at a maximum of 6400 rpm and still produce better than 485 hp, more than enough for the Fords to carry the day.

Naturally, there were a few tricks involved in making a lowly Detroit V8 outperform the world’s fastest prototype racers. However,  Ford was generous enough at the time to document its efforts in a series of SAE papers, which we relied upon heavily for this piece. (The Ford Le Mans engine papers are numbered 670066, 670067, and 670068 if you’d like to dig in yourself.)

The first order of business was to reduce the weight of the hulking FE-series passenger car V8, which was accomplished with aluminum cylinder heads, intake manifold, water pump, and timing cover, and a cast magnesium oil pan (above). The lightweight pieces trimmed the engine from 685 lbs to a far more reasonable 555 lbs, while the addition of a dry sump oiling system added 25 lbs, resulting in a net weight of 580 lbs. Ford actually considered using the 427 SOHC V8 (see our feature on the Cammer here) but ultimately it was judged too bulky and heavy for the Le Mans program, while the standard 427 medium-riser easily met the output targets.

The Le Mans dry-sump setup was rather novel in that the both the pressure and scavenge pumps were inside the oil pan, eliminating the need for an external pump and drive belt, but still provided the traditional dry sump benefits: reduced ground clearance and improved lubrication under high cornering loads. To manage the fuel slosh in cornering, Holley/Ford carburetor wizard Harold Droste developed special center-pivoting float bowls for the Holley 780 cfm four-barrel. Known as the Le Mans float bowl, this arrangement soon evolved into the familiar Holley center-hung float chamber that is still in use today.

One more surprising aspect of the Le Mans engine is its mild state of tune. At 10.5:1, the compression ratio was actually lower than in the production 425 hp Galaxie V8, while the intake and exhaust valves were slightly smaller than stock to accommodate the steel valve seat inserts in the aluminum heads. Reportedly, the camshaft was an off-the shelf NASCAR piece.

The one exotic component in the combination was the bundle-of-snakes exhaust header, in which tubes on each bank crossed to the opposite bank to correct the  exhaust scavenging when using a production-style cross-plane crank.  Employed by Coventry Climax in Formula 1 a few years earlier, the arrangement was used extensively by Ford in its Indy and Le Mans efforts in the ’60s.

To measure the output of the Le Mans V8, Ford developed an early form of road-load dynamometer that could simulate the varying speeds and loads of the road courses at Daytona, Sebring, and Le Mans. (See the dyno in action here.) In 1966 tune, the engine produced 485 hp at 6400 rpm and 475 lb ft of torque at 3600 rpm, propelling the Ford GTs to their storied 1-2-3 finish that year. For 1967, dual carburetors and detail improvements boosted the output to a reported 520+ hp.

What’s more, with its seven lazy liters, the engine could circulate the track at speeds closer to its peak torque rpm, optimizing its total efficiency. In taking the overall victory at Le Mans in 1967, the Foyt/Gurney Ford Mark IV prototype (below) also won the event’s Index of Thermal Efficiency, an award usually reserved for small-displacement race cars in the junior classes. At Le Mans, that remarkable achievement is still recognized today.