Walbro Fuel Pump Flow
As you increase your cars horsepower, the vehicle will eventually want more
fuel than the stock fuel pump can deliver.  There will be a future page
discussing your options, but in the meantime, this page will show the slight
differences in fuel delivery between the Walbro 190 (GSS242), 255 regular
pressure (GSS307), and 255 high pressure (GSS340) fuel pumps.  Both of the
255 pumps are rated at 255 liters/hr @ 45 psi (65 gal/hr @45 psi), but above
70 psi the GSS307 pump really starts to drop off.  If you run a naturally
aspirated combination or even have a large enough injector in a
supercharged application, your decision to buy the GSS307 vs the GS340 is
mute.  Both will supply adequate fuel with the fuel pressure at normal levels.  
However, if you're running a FMU with your supercharger and see high fuel
pressure levels, the GS340 is by far your better choice.  Note that the pump is
rated in liters per hour and the chart is noted in gallons per hour.  All figures
were recorded at 12.0 volts.
Walbro Fuel Pump Flow Data
 
190 lph
(GSS242)
255 lph
(GSS307)
255 lph
(GSS340)
PSI
GPH
GPH
GPH
0
56
75
75
10
52
72
72
20
48
67
68
30
44
63
63
40
40
58
59
50
36
54
56
60
32
49
52
70
28
40
48
80
22
29
43
90
12
0
36
100
2
 
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