Complex sentence: It was a very lightweight engine, the block was only 14.8 lb (6.7 kg) and even complete with all accessories including flywheel it still only weighed 133 lb (60 kg).
Split into simpler sentences: It was a very lightweight engine, the block was only 14.8 lb (6.7 kg) and even complete with all accessories including a flywheel. It still only weighed 133 lb (60 kg).