Over the winter, extensive development work was done on the 917L ("langheck" or ‘long-tail’). Using the French SERA aerodynamics laboratory, the chassis was further streamlined. Now running 17” rear tyres made its handling almost as good as the K-version ("kurzheck" or ‘short-tail’) much to the drivers’ satisfaction. Porsche also supplied a slightly larger 5.0-litre engine (vs 4.9L) using high-performance nickel-silicon cylinder-liners from NSU that improved oil consumption and reduced wear. This pushed its output up to 620 bhp. It also came with a new 4-speed gearbox, but as all the teams chose to use the tried-and-tested 5-speed gearbox the new engines were not used either.