...snip.... insisted the F-4 be fitted with Rolls-Royce Speys - meaning the F-4 had to be modified at great expense. At least the Speys were a little bit more powerful than the original J-79 engines so they did actually get something for that money.

Problem was the Speys were heavier and needed larger intakes which
increased drag and air mass flow thus effectively negating any
performance increase from the higher power engines. Upside? They didn't
smoke like the J79s (bad habit)