Thread: TBI Fuel lines

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What size supply and return lines should I use on my TBI 454? The engine is internally stock with headers, turbo exhaust, high flow air filter, and may get an aluminum intake down the road.

Thnaks, Jay

if you use 3/8" input and 5/16" return, you should be fine. Bigger lines would be an overkill with TBI....you probably could go smaller on the input but line cost is about the same for either size. Remember not to use long lengths of hose, braided or otherwise.

Thanks. Can you elaborate on the concern with using braided line? Everything I have seen has said that flexible lines are fine with a low pressure TBI system. The TBI fuel pump is only pushing the fuel at about 15psi. The braided line is rated at 100psi or more. Thank you

Its not a pressure thing...obviously a -6 braided hose will take whatever pressure that a fuel pump will deliver.

However, long runs of hose are susceptable to damage from normal conditions more so than a metal tube. Also, even though the braid is on the hose, the hose does deteriorate similar to a normal, exposed hose. Some say that the resistance to flow is greater for a hose compared to a tube but in a street application, the difference in flow is not an issue.

As I see it, the three main reasons to run a much steel tube as possible and use hose for the vibration links are:
(1) the tube is more impervious to road damage and can be clamped in a secure fashion more easily, (2) the tube appearance is much better than a run of hose, and, most
important, (3) the cost of a roll of -6 braided hose is 6X the cost of the equivalent length of steel tube.

Would a 1/4in return line be too restrictive? I am worried that I may get pushed toward 4AN and 6AN size fuel line. The 6AN should be fine for the feed but will a 4AN return be too small?

1/4 line flows 64% of a 5/16 line

1/4 line flows 44% of a 3/8 line