Inside Diameter of Fuel Tank Pick-Up?

[P-Money]

I'm going to replumb my fuel system using a bypass regulator. I plan on installing new pick-up tubes, as well as return tubes, in each fuel tank, question is, what should the inside diameter of these be? Also, should the pick-up and return tubes be the same length? If not, how far should the return tube be from the bottom of the tank?
I always hear people saying that pick-ups can really hinder the performance of a fuel system, therefore I want to do this right. Thanks for the help.

[Mr Twister]

Just did that on my boat. I was really surprised that my fuel pickup tubes were made out of 5/16 OD nylon tubing. Yes, the carbs went dry at about 4200 rpms. I Used -8 on the supply screwed into a bung that I welded to the back/bottom of the tank, and used -6 return line to a bung welded in to the top/rear of the tank. Since I was welding on the tank I also added a vent on the top/front with -6 line and a k&N breather. Also switched to an aeromotive bypass regulator. Works great.

[superdave013]

I have 3/4" bungs on the bottom of my tanks. USCG loves those. :rolleyes:
I'ed make your pick up tubes out of 1/2" od tubing at a min.
I would also put in 1/2" bungs for returns. No tubes going down in the tanks on those.
And a good vent link Mr. Twister did is much better then venting through the 3/16" hole in the cap.
Keep in mind with a by pass system you will flow much more fuel. Granted most of it will go back to the tank in the return but it still needs to be able to flow it.

[DogHouse]

Originally posted by riodog
Why are you bothering to return the fuel to the tanks. Makes more work, welding, plumbing, expense, etc. Just return the fuel to the 'suck side of the pump and make life easy!
Riodog
Perhaps to avoid heating the fuel?

[Schiada76]

?

[Mr Twister]

riodog,
You know us mechanics, gearheads, tinkerers, fools, etc. must always do stuff the HARD way. But the real question is: have you done this yourself, and does it work. I'm am not an expert in fluid dynamics, but it seems like the pressurized fuel would return back to the tank via the supply line.