possibly goofy CIS questions
 

A few questions before I start hooking stuff up wrong- I have a 1975 911S engine I am getting ready to (finally) install in my 67 912.
This is the one that might sound stupid- How do i know which line is the fuel "in" line and which is for the excess back to the tank?
Also, do I need the fuel pump in the front of my car near the tank or in the rear of the car by the engine? I have heard both, and I want to be sure before I drill holes.
Last question- what size (ID) should the fuel return line be? How much fuel goes back to the tank? Is it under any sort of pressure?
Thanks a lot

Others will know more than I, but here's my input. First, I do not believe there is any pressure in the return line, but there is some significant flow. A liter per minute or more. I suspect that the hose unions will not allow you to hook stuff up wrong. And finally, my fuel pump is right next to the tank and next to the front suspension crossmember.

My pump is in the back on a 72 911 with a 74 2.7

slater,
i have a stock '74 2.7...the fuel pump for mid-year cars ('74-'77) is on a place on the frame underneath, driver's side next to the engine. if you look, there should probably still be mounts, etc for it.
ryan

My '77 has the fuel pump in the front by the tank. Check the CIS fuel pump alternatives on Pelican.

You can also find fuel line sketches and parts there.

Good luck!

i don't guess it really matters, both ways work, but here's what one of my 911 owners workshop manuals says:

"In 1970 models the fuel pump is located at the front of the vehicle adjacent to the rear of the fuel tank. In 1971 nd later models the pump is repositioned into the engine compartment."

By that they mean underneath, in front of driver's side rear tire.
Ryan

Alrighty... I guess it's going wherever it fits best for me. Anyone know on the other questions?

I would guess the earlier configuration is better for your earlier car.

For the later ('77) models, there is a check valve in the fuel pump which, together with the accumulator maintains pressure on the supply side in support of hot starts. The return flows directly into the (unpressurized) gas tank so, as Superman says, the pressure is small.

I suggest you send a private message to John Walker's Workshop. John knows everything.

Frank