willz Posted January 13, 2014 Report Share Posted January 13, 2014 Running stock pump, stock carb, and all the emission junk is gone. How would one run the return line if I want to toss the "fuel rail" mess? 1 Quote Link to comment
wayno Posted January 13, 2014 Report Share Posted January 13, 2014 You likely have a fitting on the tank that can be utilized as a return fitting, I used the emissions vapor return line on my 71 521 to return my fuel to the tank, I just connected a hose to the end of that metal line and bypassed the vapor tank and went straight to the tank itself. My dual SUs have a fuel pressure regulator, so that made a return line easy to do. 1 Quote Link to comment
ggzilla Posted January 13, 2014 Report Share Posted January 13, 2014 Just make sure the tank is still vented. Carbureted Datsuns do not not need a return line. Only ones from mid-1970s have them but its for emissions to lower evaporated fuel. 1 Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 I have a fuel cell, two lines in the bottom.. one will be for return and one will be out. It also has a vent in the top... my question lies at the carburetor because I really wanted to take out the hardline that hugs the right side of the valve cover (looking at the front of the truck) but from what I've read there is a little hole on the return so that the carb still gets the adequate amount of pressure? what can I do to re-plumb this? will I need a pressure regulator to vent my excess pressure? 1 Quote Link to comment
ggzilla Posted January 13, 2014 Report Share Posted January 13, 2014 It doesn't need a return line. If the float is set correctly and pressure is within stock limits and needle valve ok and air fuel mixture adjusted correctly it will be OK. The restriction in the line is so the fuel runs into the fuel bowl and doesn't simply all return to the tank. If your goal is to clean up the engine compartment I'd skip the return line. 1 Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 I'll eventually be putting in an electric fuel pump as well so I would assume I'll want the return for for the fpr? 1 Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 oh man that blows, I was looking around the garage and found an extra (and brand new) aeromotive adjustable fuel pressure regulator and gauge kit... but its for an outlet pressure of 5psi (minimum) 1 Quote Link to comment
datzenmike Posted January 13, 2014 Report Share Posted January 13, 2014 The return line on the L20B is essential to keep fresh cool fuel from the tank circulating past the carb. This prevents the fuel from boiling on hot days making restarts difficult. (a real problem with the hotter L20Bs) In addition the fuel in the tank is constantly, (though slowly) run through the fuel filter reducing sediment build up in the tank. Bad idea to remove it. 1 Quote Link to comment
JNHEscher Posted January 13, 2014 Report Share Posted January 13, 2014 The return line on the L20B is essential to keep fresh cool fuel from the tank circulating past the carb. This prevents the fuel from boiling on hot days making restarts difficult. (a real problem with the hotter L20Bs) In addition the fuel in the tank is constantly, (though slowly) run through the fuel filter reducing sediment build up in the tank. Bad idea to remove it. I've been reading up on this for mine. I have a '74, but the motor was replaced with an L20 that has the restricted return hard line. My truck being a 74 has no return line, but using the vapor line looks like a viable option. 1 Quote Link to comment
kelowg Posted January 13, 2014 Report Share Posted January 13, 2014 Make your own hardline setup. Get piece of metal rod to fit inside section of return hose and drill small hole in it. put into said hose. Reg isnt needed with stock carb and they make 3-5 psi elect pumps. Dont over think it. 1 Quote Link to comment
kelowg Posted January 13, 2014 Report Share Posted January 13, 2014 Yes, vapor line works fine even on my 71 1 Quote Link to comment
datzenmike Posted January 13, 2014 Report Share Posted January 13, 2014 Except it's a vapor line for venting the tank. Not saying you can't just it's not for returning fuel. 1 Quote Link to comment
JNHEscher Posted January 13, 2014 Report Share Posted January 13, 2014 Just have to make a vent at the tank, unless the cap will allow enough flow. 1 Quote Link to comment
Kirden Posted January 13, 2014 Report Share Posted January 13, 2014 The vent line doesn't equate in this because he is using an after market fuel cell that has a built in return and output fitting as well as a vent fitting. That being said my 74 doesn't have a return to the tank. There isn't a need for a stock engine, but it is added prevention by filtering the fuel and keeping cool fuel near the bowl as Mike pointed out. If you want a clean engine bay go without the return line, if you want something that looks more performance based and adds some security, add the line and a FPR 1 Quote Link to comment
datzenmike Posted January 13, 2014 Report Share Posted January 13, 2014 It isn't there for looks, it's there to solve an engineering problem to prevent vapor lock, mainly on the L20B engine. Removing 'stuff' for looks is ill advised. You'll be back next summer complaining your truck doesn't start. The best side advantage is filtering of the gas. 3 Quote Link to comment
DanielC Posted January 13, 2014 Report Share Posted January 13, 2014 Running evaporative emissions equipment does NOTHING to hurt the performance of the engine. It simply controls the evaporation and escape of gasoline vapors. This is a good thing. Gas vapors that escape is gasoline that you have paid good money for, that is not being used to move your vehicle. In a car, it keeps gasoline vapors out of the passenger compartment. The gas vapors are simply held, and when you start the engine after it has sat for a while and is cold, the vapors are fed back into the engine, and you need the richer mixture then anyway. I can understand wanting to remove EGR. I can understand wanting to remove devices that retard the timing under certain conditions. But controlling evaporative emissions, like (PCV) Positive Crankcase Ventilation is a good thing. Putting an electric fuel pump on an older Datsun engine, that had a mechanical pump is also not a really good idea. The mechanical fuel pump does not really push fuel into the Carburetor, when the engine is running. The motion of the lever on the camshaft eccentric simply pulls a diaphragm in the fuel pump against a spring. The spring is balanced against the needle valve in the carburetor to allow fuel into the carb, only when the carb needs it. Also, the mechanical fuel pumps flow is RPM dependant, the pump moves more fuel, at higher RPM, when the engine needs more fuel. An electric fuel pump does not do this. It tries to cram as much fuel into the carbs at idle as it does at 7000 rpm, and WOT. 1 Quote Link to comment
Z-train Posted January 13, 2014 Report Share Posted January 13, 2014 The return line on the L20B is essential to keep fresh cool fuel from the tank circulating past the carb. This prevents the fuel from boiling on hot days making restarts difficult. (a real problem with the hotter L20Bs) In addition the fuel in the tank is constantly, (though slowly) run through the fuel filter reducing sediment build up in the tank. Bad idea to remove it.Read this,know this,BE this. 1 Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 so back to my original question... How would one run the return line if I want to toss the "fuel rail" mess? I dont want to delete the fuel return line, I wanted to clean up the area around the carb from those hard lines. and make it a little less messy what I ended up starting last night was cutting off the extra lines on the "fuel rail" so it looks like it never came with them, and then running some new black cloth braided line for the vacuum (Ive got about 25ft of the stuff left over from my VW days) Quote Link to comment
Kirden Posted January 13, 2014 Report Share Posted January 13, 2014 You should be able to run a restictor in the return hose like Kelowg described Make your own hardline setup. Get piece of metal rod to fit inside section of return hose and drill small hole in it. put into said hose. Reg isnt needed with stock carb and they make 3-5 psi elect pumps. Dont over think it. Or you could get fancy and go with a FPR. Do you have a weber or the stock carb? If you have a weber I've seen people replace the plug on the other feed line with a fitting and run the return line from there with a FPR or restrictor in that line. If not you could make a T of some sort before the carb with the restrictor or FPR between the T and the tank so that the carb is always getting the required fuel. 1 Quote Link to comment
Kirden Posted January 13, 2014 Report Share Posted January 13, 2014 You could even go with something like this: http://www.rivayamaha.com/RivaStore/product_page.asp?Category=Fuel%20Line%20Return%20Restrictor Just make sure the sizes are correct. 1 Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 I'm running the stock carb for now. Eventually I would like to do a dual side draft setup but I don't think I can afford to buy a set at the moment. With all the things i've been buying lately for the truck, I might have to go back to doing some bodywork haha 1 Quote Link to comment
Kirden Posted January 13, 2014 Report Share Posted January 13, 2014 I did the same thing when I bought my truck. Probably dumped $1500 into a $700 truck in less than a month... Just a word of advice, get it running and spend a while with it before you make any huge decisions. I've lost more than the truck is worth in useless parts now that I have (or atleast hope to have) a final direction. Quote Link to comment
willz Posted January 13, 2014 Author Report Share Posted January 13, 2014 Ohhhhhh I know, haha I've been driving the truck for almost 2 years now, (driving from san diego to seattle a few times) the only changes I've made since it was last running ( a few months ago) was a fuel cell, new hard line, smog delete and all new bushings/ball joints/tie rods/center link/idler arm and freshened up the back half of the frame and underside of the bed After I order my zg flares, I'm into it for around $4k. I know the motor will eventually be a 2.2 and sidedrafts. I'm trying to keep the build somewhat period-correct+ 1 Quote Link to comment
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