I'm getting ready to do the fuel system, I just wanted to figure out a few things.
The factory fuel supply hard line for the old carby is 6mm inside diameter, is this acceptable to use for EFI?
If not I'll have to run rubber fuel hose the length of the car, but is 8mm or 10mm inside diameter the better one?
Also, I'm having some issues with the 280ZX clutch pedal. It sits nicely but the master cylinder fork won't reach it. What clutch pedals are you guys using in manual conversions?
I used the 6mm line as a fuel return and used a 5 metre roll (no joints!) of 3/8 inch EFI hose from the EFI pump to the engine fuel rail. I didn't follow the original line all the way. There is a crossover point under the car along the chassis rail where it moves from inside to outside. I didn't want to run the hose across here so I continued to run the hose on the inside, to close to the clutch line and then across the firewall to the other side. The return hose from the EFI rail just hooks up to the original feed (now return). this will plumb back to your swirl pot or tank, take your pick. I put the return back into the swirl pot and the top, swirl pot overflow line is the back to the tank. (Ps I used a long aluminium skid plate under the car, about 70cms long to protect the fuel line at the shallowest point of the chassis rail, right around the original hard line crossover. I also used split convoluted electrical tube over the whole length of the fuel hose as extra protection. To hang the hose, I used metal electrical "C" clamps you see for electrical plastic conduit tube attached to a wall etc. They dont crimp the hose and I used the original holes etc on the chassis rail to mount the screws for the brackets. A lot of dirty work under the car but I think I did a good job getting a good volume of high pressure fuel to the engine bay, safety being my biggest concern. Got a blue slip with this arrangement too).
My clutch pedal is from a 120Y IIRC, so long ago now when i first did this conversion, I cant remember exactly. It had to be redrilled so the clevis would sit in the right position and put the rubber on the pedal at the same height off the floor as the brake. If you really want to use the zx pedal, you may have to engineer a solution with a steel spacer plate or something.