The "Big Valve" Twin Cam was a project of Lotus' Engineering Director Tony Rudd. Rudd reduced the deck height by to raise the compression ratio to 10.5:1, increased the diameter of the inlet valves to , modified the inlet runners' shape for the larger valves and installed Super Special Equipment D-type camshafts. Power was increased 20% over the regular engine's . Big Valve engines were offered in the Elan Sprint, Elan +2 130, and Lotus Europa Twin Cam Special models. Cam covers for Big Valve engines had the words "Lotus" and "Big Valve" cast in raised letters across the front of the cam cover. The portion of the cover over the camshafts had raised ribs cast in.