Marvellous machine, yes. But not marvellous machining. Far from it. Initially, anyway. Due to Rolls-Royce's limited capacity, production of the Merlin had to be farmed out to other manufacturers.

Ford, was but one of several different companies to produce the Merlin. But it was almost a case of them not doing so. The reason, was terrible, slack production tolerances on the part of RR. They would build each engine individually. So much so, that parts from other, apparently identical engines, could not be guaranteed to fit other sister Merlin's.

So when Ford was asked to produce the Merlin, it said that in order to do so, they could only produce items within much tighter production tolerances.

Why? Because Ford were the first to volume manufacture cars and engines. Something that was very necessary in mass production. Ford had to ensure that a part used in several models, could be switched at will, directed to where they were required, something Rolls-Royce were not capable of.


The British government had Rolls-Royce give assurances that they would tighten up on their production tolerances. Once proven, Ford began manufacture, although it was not always possible to fit parts supplied by RR to Merlin engines built by other companies.

The Merlin also found its way into other applications, such as MTB's and tanks, although somewhat de-tuned in the case of tanks.