datzenmike Posted February 17, 2015 Report Share Posted February 17, 2015 Hey, on your Datsun which is larger diameter.... the fuel line from the tank, or the return line to the tank????? Only '75 and up L20B engines had the return line. Not sure abour A series. Include EFI engines as well with rear pumps. Quote Link to comment
MicroMachinery Posted February 17, 2015 Report Share Posted February 17, 2015 Generally, the return line is equal to or larger than the supply line. Quote Link to comment
datzenmike Posted February 17, 2015 Author Report Share Posted February 17, 2015 Tell wayno. :lol: ... Well he says the 720 is larger into carb and smaller return. Now this may be because the pump is in the back pushing forward but all the L series I have seen the return is always larger. Maybe this is specific to the 720??? Quote Link to comment
510freak Posted February 17, 2015 Report Share Posted February 17, 2015 620? 720? which is it.. :poke: 1 Quote Link to comment
MicroMachinery Posted February 17, 2015 Report Share Posted February 17, 2015 I should be out at my shop tomorrow. My 80 720 has an L series, so I'll check and see which one is feeding it. 1 Quote Link to comment
datzenmike Posted February 17, 2015 Author Report Share Posted February 17, 2015 620? 720? which is it.. :poke: Well it started out as a general statement that the return line is smaller which I disagree with. Wayno is sure that his 720s are this way... and maybe they are, and maybe all 720 are. I'm just sure that the return line is usually larger at least on all the Datsuns I have seen. Perhaps the 720 is different because the pump is in the rear and L series are on the engine. Quote Link to comment
wayno Posted February 17, 2015 Report Share Posted February 17, 2015 I have been doing these 720 conversions for a while now, and I don't pipe my fuel lines goofy, they are in stock configuration. Here is a stock 720 kingcab tank, the huge hole is the fill tube, the big fitting high and to the right is the vent for the fill tube, the fitting to the right low is the pickup tube, I can look in the fill hole and see the pickup tube, the 2 fittings to the left on top of the tank are the return line and the vent that goes all the way to the engine compartment on the driverside, in this photo, you can see that the pickup tube is obviously larger than both the tubes on the top of the tank, on the 720, the feed line is larger than the return line. Quote Link to comment
datzenmike Posted February 17, 2015 Author Report Share Posted February 17, 2015 Then this must be because the pump is in the rear. Pretty sure the other Datsuns are the other way. 2 Quote Link to comment
HOGIE Posted February 17, 2015 Report Share Posted February 17, 2015 I removed both the return and fuel line from my 78' 620 today (no oics) and replaced the fuel line today (go to just one line). They are the same size. Couldn't say about 720 though. Quote Link to comment
Z-train Posted February 17, 2015 Report Share Posted February 17, 2015 78 620 both are 6MM. Quote Link to comment
bananahamuck Posted February 17, 2015 Report Share Posted February 17, 2015 Just checked ,,, 1980 720 ,, same size at the firewall not ambitious enough to crawl under and check at tank though Quote Link to comment
MaxG Posted May 28, 2021 Report Share Posted May 28, 2021 I know this thread is old, but does anyone know the inside diameter of the filler ventilation hose for the 720 fuel tank shown in @wayno'spicture above? Mine is leaking like crazy Quote Link to comment
datzenmike Posted May 28, 2021 Author Report Share Posted May 28, 2021 This is not a filter. It's a check valve to prevent gas draining back out in the event of a roll over. If you don't drive like an idiot drifter your probably safe enough to just eliminate it if you can't find a replacement. Quote Link to comment
hang_510 Posted May 31, 2021 Report Share Posted May 31, 2021 my 72 510 wagon had same sizes lines. Quote Link to comment
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