599: maybe you are remembering: The Man “who put power into the Merlin” Sir S.Hooker, Not Much of an Engineer{Airlife,84}: Ford/UK (for the Trafford Park Agency Factory) came to him with a "problem": he assumed they would confess that RR's tolerances were beyond auto-skills; but it was the reverse: inter-changeability, essential to permit Model T to be “repeatable” by diluted labour, alien in Aero, required precision beyond RR’s practice. Ford took a year to engineer “very good” Merlins, seen as 30% cheaper than RR.
This was however not a "blunder". Few/no Aero products will be built in auto quantity.