I do know why they had engine size restrictions. Back in the late 1960's Ford was putting 427s in the Ford GT 40's and the European car manufactures couldn't compete with the Americans on that scale.
Gas mileage requirements will probably keep engine size smaller.
Follow up:
http://www.europeanlemansseries.com/en/s02_corporate/s02p14_reglement.php
I guess that was only for the Grand Touring Challenge division.
“I do know why they had engine size restrictions. Back in the late 1960’s Ford was putting 427s in the Ford GT 40’s and the European car manufactures couldn’t compete with the Americans on that scale.”
At that time the ACO limited displacement to 7 liters, and for whatever reason none of the European manufacturers built an engine anywhere near that large. As one example, Porsche stuck with a 3.0L engine in the 908 and didn’t go larger until the homologation requirements for Group 6 (which had a 5.0L limit) in the late ‘60s were decreased from 50 cars to 25, at which point they developed the 917.
The rest is, as they say, history. That era was a great one for endurance racing.