"...The Rover 3.5 litre V8 began life as the Buick 215, an all-aluminium engine introduced by Buick in 1960/61. The compact engine was lightweight, at just 144 kg (318 lb).The Rover engine was heavier but stronger than the Buick engine, with a dry weight of about 170 kg (375 lb) ..."
[Source:http://www.lr-mad.co.uk/en/rover-3-5-v8-engine]
However,i think it was without ancillaries,because:
Audi V8 3.6 engine weighed 215kg with all fluids and was 508mm long.
