I Want my 4.09 Spit FM's back.........

[JtD]

Originally Posted by WTE_Galway

All the Tilly Orifice did was restrict the maximum rate of fuel flow to the float chamber and hence reduce the rate of flooding and resultant over rich mixture cut-out in the SU carbs fitted to early Merlins.
...
but the problem remained and sustained inverted flight was still impossible.

The Tilly Orifice reduced the fuel flow to the amount of fuel needed at maximum power - 12/16 lb of boost and 3000 rpm. At that power setting, the engine would not cut out in sustained inverted flight due to flooding.