Converting from carburettor to EFI normally requires a different fuel delivery profile, the existing 240Z fuel lines are not enough for my custom ITB setup. Carbs require low pressure fuel volume (flow). EFI requires good steady high pressure fuel. Long story short fluid mechanics dictate that factory carburettor fuel line sizes are rarely the correct diameter to sufficiently support EFI fuel requirements.
The factory fuel line sizes in my 1971 Datsun 240Z are 5/16″ for the supply and 1/4″ for the return. The 5/16″ supply line might be sufficient to remain as a supply line. However the 1/4″ return line is very likely to restrict flow. This would slowly increase fuel pressure from back flow phenomena. This is not ideal when your aiming for constant pressure and flow behind your injectors!
I want to run a new 3/8″ supply hard line but my challenge is that all the running gear and hardware is still in the car. So how am I going to make 240Z fuel lines and fit them? With great difficulty of course!
Removal of the old
The first step was removal of the old 1/4″ line. I really wanted to remove the line in one piece if I decided to return the car to factory and at least use as a template for the new line. Alas this was not a story meant to happen!
After removing the clips and rubber insulators securing the hard lines to the transmission tunnel, I cut the 1/4″ line under the brake booster (RHD car) before the first insulator block on the chassis rail. After this was cut the was removed easily enough straight out the rear. I recommend removing the fuel tanks for this!
The new 240Z fuel lines
I started by forming up the new 3/8″ line from aluminium tube with a 1mm wall section. The tube was black painted and I expected that paint to be knocked off in locations once I was done feeding it back under the car. The tube came in a coil and in hindsight I wish I has a tube straightener!
Reviewing the old line, I figured that I only needed a bender for the dog leg than passes around the diff and moustache bar next to the fuel tank and the other bends are likely to be completed with hand techniques. I proceeded to form up the new line with the old as a guide…..
So, did the new 240Z fuel line fit?
Yes and no, well after a bit of fine tweaking it did. Mirroring the old 240Z fuel lines is the best thing I can recommend. I do not recommend working around installed hardware if you can avoid it!
I was working on the car on jack stands, I do not own a hoist. After some thinking I was able to feed the new line up into the engine bay from underneath and bring it back through the transmission tunnel over gearbox and diff mounts. The line clicked into place to my surprise. I decided ‘bugger it’ and left the line in the car making minor hand tweaks as I proceeded to clip it off. Barb house flares were added at the ends of the line and job was done!
I recommend installing 240Z fuel lines on a free body. Working around the existing hardware should only be done as a last resort in my opinion. I have a concern that I may have stressed the line having to move some parts of the line back and forth a very small amount. Back bending is a no no. Proof will be in the pudding when high pressure fuel is pumped through the line for the first time! Apart from that I am pretty chuffed with how the line turned out.
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