In 1961 Bristol stopped building the 2.2-litre version of their six cylinder engine for internal use, but agreed to continue producing the 2-litre version for AC until 1963. At the same time, the AC six cylinder engine had reached the end of its development potential.

In 1961, Texan Carroll Shelby approached AC's owner, Charles Hurlock, with a proposal to install a Ford V8 in the Ace chassis. AC agreed, and began adapting