Petrol is pumped into the carbs that have floats etc but the fuel does not cut off when the chambers are full - the excess fuel flows back out of the carbies back to the tank via external pipes than join up to both carby over flows.
If you have fuel leaking then there is a crack in on of these pipes (or not there) or they are blocked preventing the fuel going back to the tank.
Garry
				
			 
			
		 
			
				
			
			
				REMLR 243
2007 Range Rover Sport TDV6
1977 FC 101 
1976 Jaguar XJ12C
1973 Haflinger AP700
1971 Jaguar V12 E-Type Series 3 Roadster
1957 Series 1 88"
1957 Series 1 88" Station Wagon
			
			
		 
	
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