# 1/2 inch fuel lines



## jtwoods4 (Dec 22, 2011)

69 GTO....

Will the stock fuel lines feed a 550 hp 455 engine?

At what point do I need to switch from stock fuel lines to larger 1/2 inch fuel lines?


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## lars (Sep 28, 2004)

The stock lines will easily support 550, but even near-stock GTOs will often suffer fuel starvation at the top end of 2nd gear with the stock mechanical pump. This is not a function of the fuel lines, but simply a matter of a long line, fuel mass under hard acceleration, and the limitations of a diaphragm-type pump trying to "suck" a large mass of fuel against the g-force of acceleration. Going to a larger line actually makes this situation worse.

Rather than going to a larger line, any Pontiac used for drag racing or serious stop-light Grand Prix action needs a good electric boost pump back at the tank. This will easily allow the stock lines to support fuel consumption for anything under 700 horse. You can wire the electric boost pump with a "select" switch so you can run only off the mechanical pump for "daily" use, and then switch the electric boost on for "action." This will solve any fuel supply problems you might have. I also always recommend that any system using an electric pump use a fuel return line so that the electric pump is never "dead headed": Dead heading the electric pump drives amperage way up and dramatically shortens pump life. Use a return-style regulator, like the Mallory, or run a return line with a simple bleed oriface to keep the fuel circulating. This also effectively eliminates vapor lock on hot summer cruising days.

Here's a system I built for a 500-horse 455 in a Firebird: This is a simple bleed-oriface return line system used with a Holley "Blue" boost pump at the tank and a stock mechanical pump on the engine. The engine had severe lean-out issues prior to installation of the boost pump and return line:









Although this is a Chevy I built, it shows a slightly more sophisticated system using a Mallory return-style regulator. This engine dyno'ed at over 500, and runs great on 3/8 lines and an Aeromotive pump system back at the tank (hey... at least I have a round-port Pontiac in the background..!):









Lars


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## jtwoods4 (Dec 22, 2011)

Wow! Beautiful engines! Thank you for the detailed information.


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