Fuel Line Length

[Bren]

I've searched both forums for fuel line length but only find results for fuel line size. I'm trying to buy cunifer brake and fuel lines, but I don't know what length to buy for the fuel lines (mechanical pump with return line). One person has suggested 10' is enough, but that sounds short to me. I know the exact length will depend on how I run the lines, but how much should I buy (9', 12', 15', 18', more, less)?

By the way, I plan on buying 25' for the brake lines.

[68GT500MAN]

Take a piece of string and run it along your planned route, then measure its length and add some.
Doug

[Bren]

Take a piece of string and run it along your planned route, then measure its length and add some.
Doug

Ordinarily, I'd say that would be the best method. But I don't have the kit yet, and I'm trying to buy everything before it's needed as I'm on a bit of a tight schedule. So, that method isn't available to me.

[2bking]

Bren, I have been following your build thread so I know you don't have your kit yet. The lines that come with the kit are steel but have a copper plating on the inside and olive drab color coating on the outside. Others may have a say about rust in the long term but I don't think you need to replace them unless you want a stainless look. The kit supplies two 60" 5/16" lines (pressure) and 2 60" 1/4" lines (return) . I used what came with the complete kit for both pressure and return but it was hidden from sight by going through the tunnel. That route only required one piece of each size. I used 3/16" stainless for the brake line and 20' would have been enough if I hadn't messed up one of the long sections. After I messed up that one, I found the kit supplied brake line was excellent for prototyping the bending and transferred the bends to the real line when I got it right.

[Bren]

Bren, I have been following your build thread so I know you don't have your kit yet. The lines that come with the kit are steel but have a copper plating on the inside and olive drab color coating on the outside. Others may have a say about rust in the long term but I don't think you need to replace them unless you want a stainless look. The kit supplies two 60" 5/16" lines (pressure) and 2 60" 1/4" lines (return) . I used what came with the complete kit for both pressure and return but it was hidden from sight by going through the tunnel. That route only required one piece of each size. I used 3/16" stainless for the brake line and 20' would have been enough if I hadn't messed up one of the long sections. After I messed up that one, I found the kit supplied brake line was excellent for prototyping the bending and transferred the bends to the real line when I got it right.

Excellent. Thank you. And I like your idea about using the steel lines as practice for bending and routing.

So, if I'm upsizing the supply fuel line to 3/8", should the return line be 5/16"? Does FFR supply a connection to the fuel tank for the return line? If so, how big are those lines? (It seems useless to upsize the fuel supply line to 3/8" if you still have to suck the gas through a 5/16" tube in the tank)

[2bking]

I think you have settled on a 427 engine and most builders using the large displacement engines go with the 3/8" from tank to engine. There are fuel line size calculators like this one, http://www.lmengines.com/fuel_lines_calc ,on the internet that is useful for determining line size. Remember tubing is measured on the OD and the calculator works on ID dimensions.

Flow through piping has restrictions in both length and bends so a short piece of 5/16" line is equivalent to a longer piece of 3/8" by the ratio of the inner diameters squared. So, 12" of 5/16" line is approximately equal to 18" of 3/8" line. A short radius bend is equivalent to say 12" of straight line. A fuel filter may be equivalent to 48" or more. So for the calculator, just add length to compensate for the restrictions. Remember the results you get will be for wide open throttle (WOT) at maximum RPMs. You can Google the fittings and filters to find equivalent line length or pressure drop.