Gravity filled carb is your problem.
On later marks of Spitfire and Hurricane this was fixed.
Carburettor versus fuel injection
Early in its development, the Merlin engine's lack of direct fuel injection meant that both Spitfires and Hurricanes, unlike the Bf 109E, were unable to simply nose down into a steep dive. This meant a Luftwaffe fighter could simply "bunt" into a high-power dive to escape an attack, leaving the Spitfire sputtering behind, as its fuel was forced by negative "g" out of the carburettor. RAF fighter pilots soon learned to "half-roll" their aircraft before diving to pursue their opponents. The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, and hence the greater density, of the fuel/air mixture fed into the motor, compared to injected systems. In March 1941, a metal diaphragm with a hole in it was fitted across the float chambers. It partly cured the problem of fuel starvation in a dive, and became known as " Miss Shilling's orifice" as it was invented by a female engineer, Beatrice "Tilly" Shilling. Further improvements were introduced throughout the Merlin series, with Bendix-manufactured pressure carburetors introduced in 1943.
