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fuel return line needed on 73?

401 Views 7 Replies 6 Participants Last post by  briann510
on our 73 we have the stock metal lines to the SU carbs with a return line back to the tank. this is a mechanical fuel pump only.

i am tired of the metal lines getting so hot we get vapor lock in hot weather and want to replace them all with rubber lines.

is it wise to discards the return line or should i T into the carb lines with a return line like stock?

engine picture

Video of our 240z before the 2.5 inch exhaust added (7.7 mb)

Post Edited (Oct 20, 12:33am)
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How about putting a type of insulation over the lines to keep them cooler. I personally wouldn't like to have all that extra rubber hosing going every-where, it just asking for problems.

you need the return line; without it, your float bowls can overflow, and you could have an engine fire. Besides, the increase in fuel flow helps prevent vapor lock. I don't think you will help vapor lock by using a rubber hose; indeed, I would think you will make it worse. ( I believe that a rubber hose would not dissipate residual heat as fast as a steel one) Plus, long rubber lines carrying pressurized fuel make me very nervous....the more steel lines, the better, IMHO. Especially near the fan..... Stock 240's had insulation wrapped around the steel lines, does yours still have it?
I run an electric pump full time and don't use the mechanical pump any more, but I use the stock fuel return line. So if I have vapor lock, the electric pump rapidly circulates cool fuel from the tank through the lines and back to the tank via the return. In other words, I don't have vapor lock. Running an electric alone requires some rewiring of the stock73 fuel pump relays; this is detailed in past postings by me which were kinda long, so find them with an archive check.73's came from the factory with both a mechanical and an electric pump, what happened to your electric?
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Ghost is correct, you need the circulation back to the tank with a return line. The V-3 kit that I retrofitted back in the day included asbestos shieldng for the fuel lines and we also reamed the return line to a bigger size to allow more volume of fuel to circulate. I don't remember if it was specified or a trick we cooked up on our own. Good luck
i now have the lines wrapped with some of that foam water pipe tubing and some reflective tape for the temp fix (ugly as heck).

i noticed this week the foam is melting in a couple places so i need to get some real heat wrap tape wrap to use.
Has anyone tried the injector cooling fan setup they used on the 280ZX's? It should bolt on - just need the thermostat housing with another slot for high temperature temp switch.
My '72 doesnt use the return line. In fact, my overflow lines simply vent into the engine compartment. I know that's a fire hazard, but I've never seen them appear wet at the ends - and i've looked, believe me.
my overflow lines dump out under the frame.
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