Graham is pretty much on the money, but doesn't mention that part of the reason is modern ethanol laced/winter blend fuels. Modern fuel injection systems operate at much higher pressures, and therefore don't have vapor lock problems that the old D-jets had @ 30+_ lb presure.
If you get all the other parts in the fuel delivery and managment system working to spec (including trigger points-often overlooked for both cleanliness and point accuracy), plus ignition, proper plugs/wires andtrigger points, and kickup the fuel pressure regulater a few point to 32 psi or so, your car will be OK with modern fuels.
as the saying goes, ask me how I know...

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Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1973 Citroen DS23 EI five speed
Past vehicles;
1959 Thunderbird convertible/430
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang