[Jay S]

I have tanks systems feeding a carb, there are a few different issues that you run into feeding carbs versus FI systems. When feeding a low pressure carb the pump flow rate is about 30% higher at 7 psi than feeding 40 psi on a EFI system. All that extra fuel gets returned constantly unless your at full throttle, with the extra fuel flow the fuel is extra warm when pushed thru a 3/8” line. I have noticed fuel even gets warm thru 1/2” line on my cars with the tanks system. With the small line and oxygenated fuel, feeding a carb, fuel pressure is not as consistent, and depending on the fuel and your carb set up vapor locking can be an issue. It isn’t that the 3/8” line won’t work most of the time, it will, but it does not work near as good as 1/2” line when condition that are hot or feed near as much HP.

With a carb set up the best results are to set it up so the fuel line from the pump to go directly to the carb and the regulator plumped in after the carb. Similarly to what I am saying with 3/8” line versus 1/2” line, it isn’t that you can’t put the regulator before the carb and plumb into the return, but it works best set up differently, less prone to vapor locking and more constant supply.

If you were determined to run 3/8” line, you might look into using a smaller 190 pump instead of a 255.