73 240z Turbo with a 75 280z gas tank

[J240ZTurbo]

I installed a 1975 gas tank into my 73 240z turbo swap and know I see that the 240z vapor tank wont work with the 75 280z gas tank, is this thing necessary anyway? Please let me know if you can help or are there any other good ideas out there?

thanks,

juan.

[Zcavalry]

Its not a must have. I just ran the gas tanks vent line into part of my intake. Idk how good of an idea that was though, could a narley backfire do some damage with this setup? I had a few with no issues.

[J240ZTurbo]

anyone else?

[Tony D]

My vapor tank works just fine with the 75 tank, make some 15mm adapters and plug some vents save for the top one, and connect the tubes.

 

I have been running a 1975 tank in my 73 since about 1988...

 

All my vapor hoses are 10mm though, not the 15mm that came stock. I adapted them all down with the same sort of nylon adapters Nissan used so I could make tank vent hoses out of normal available fuel hose, and not try to find 15mm (5/8") vacuum/pcv hose suitable for gas transport. First car I did it to, and because of the results, was not the last. I can put 5PSI in my tank, and it will HOLD there overnight with the crankcase vent and fuel / fuel return line blocked off properly.

 

That's fuel system integrity! No gas smell in my car. Since 1988.

[J240ZTurbo]

tony can you please make me a quick drawing on how you did this? Yes the 240z vapor tank has 5 inlets and the 280z has 4 I dont know what to eliminate?

[Tony D]

My vapor tank works just fine with the 75 tank, make some 15mm adapters and plug a vent (not the top one), and connect the tubes.

 

I have been running a 1975 tank in my 73 since about 1988...

 

All my vapor hoses are 10mm though, not the 15mm that came stock. I adapted them all down with the same sort of nylon adapters Nissan used so I could make tank vent hoses out of normal available fuel hose, and not try to find 15mm (5/8") vacuum/pcv hose suitable for gas transport. First car I did it to, and because of the results, was not the last. I can put 5PSI in my tank, and it will HOLD there overnight with the crankcase vent and fuel / fuel return line blocked off properly.

 

That's fuel system integrity! No gas smell in my car. Since 1988.

 

 

Is that any clearer? No chance in hell of getting a drawing, the panels are in place and have been since '90, don't plan on removing them any time soon---plus they are in So Cal and I'm in Tokyo right now making looking at them nigh near impossible! My explanation of the conversion process for this car and my 510 Wagon is elsewhere but I'll recap it again briefly:

 

Take small stubs of real 15 mm (5/8") fuel line (not Heater Hose!) of about 2.5" in length, do whatever you normally do to the ends---I wrap mine in electrical tape so they do not extrude through unlined worm gear clamps. Install these on the vents, with clamps. Plug the lowest vent line you can, the highest one is really the only one you need, and REALLY you can connect the lower one with the higher one with 10mm "T" fittings and a length of 10mm fuel line to retain that vent's function.

 

Anyway, when you have all the little stubs of 15mm hose on there and clamped, then stick the 15x10mm adapter fittings in there and run the 10mm fuel line up through the floor raise the tank and strap it in. Then connect the fittings on the tank using the same method: 15 or 12x10 adapters. I have "T'd" hoses together and hooked them to a common port as well as put them all together and eliminated the tank when I couldn't get one---I would NOT recommend not having an expansion tank with this setup---it WILL hold pressure and can sink your floats on the SU's if you fill on a cold morning and let the car sit in the sun---there will be over 5psi in the tank by noon, and this fuel will either be discharged to your crankcase, or into the SU's and down in to the cylinders. My car uses a non-usa filler neck to vent overboard....to the ground. Save the planet...

 

With the 10mm hoses, you can run them three at a time almost through the stock floor hole, and shrink tube the opening. Cap the rest with plastic caps or other airtight sealants to keep cabin integrity. RTV works nice if you put masking tape on the bottom of the opening and fill the penetration (the little vertical tube) solid with RTV and let it solidify.

 

You will do this ONCE. The 10mm or 8mm fuel line (I have used both, 15mm is WAY overkill!) lasts FOREVER compared to the original lines. I ran EFI hose since I had it, but carburettor hose should be fine. Any of the vent lines only need carbureted rated hose---there will never be that much pressure in the tank, even with EFI. DO NOT use carburetted fuel line hose on fuel suction, pump outlet to hardpipe, or hardpipe to fuel tank return fitting!

 

One other thing is that on the 1/4" fitting at the front topish portion of the tank (if I recall) is where I ran my EFI fuel return---there may have been one that was easier to get to---so I used EFI Fuel Line Hose to that one from the Vapor Recovery line. VENTING is now accomplished by taking the highpoint vent (1/4") to the topmost portion of the tank, making a 'double loop' and ziptying it in place above the expansion tank, then running it out the same hole in the floor where it vents through a K&N filter. You can do this through the expansion tank top fitting as well---the one that used to go to the vapor line---I'm assuming you are using this for fuel return as well, so you have to make an alternate vent! Just double loop the hose, zip tie it in place, and then run the vent outside to a small filter so bugs and dirt don't get in an plug it. Venting off the top of the expansion tank will RARELY if EVER let gas dump to the ground in raw form. Venting directly off the top of the tank through a loop and without an expansion tank can get raw gas dumping on the ground so that is why you want to keep that expansion space available, especially if you FILL your tank!

 

Got to run to dinner. Any questions ask, this was done in a rush and I may have garbled it a bit. Sorry.

[Tony D]

Back from dinner, realized I mixed up my original 73 tank and 75 tank in some respects. When using the 73 tank, you have to use the top 1/4" vent port to run your return line to (the stock 3/16" runner is too small) so you need a supplemental vent for expansion and contraction.

When you use the 280Z tank, you can use the regular 280Z return line, it's big enough---so the stock high point vent is OK to route to the expansion tank.