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MG MGB GT V8 Factory Originals Technical - Fuel flow requirements of bigger Rover V8s?

How much fuel flow would a warmed-over Rover 4.6 take? I don't mean pressure -- I figured out a long time ago that my Carter likes 5psi -- I'm talking flow. 70gph? 120gph?

Also, has anyone found it beneficial to re-plumb the system with 3/8" fuel lines? I am thinking that the MGB's 5/16" lines are not fat enough to allow good flow to the V8.


70 gph would equate to 5 miles per gallon at 140MPH, should be OK.
George B.

A worst-case scenario would be to believe that your Carter can deliver 600 CFM and at 17 : 1 air/fuel ratio would yield 35 cubic feet; about 5 gallons U.S. per minute or 300 gallons per hour.
George B.

Before someone else corrects my math: 35 cubic feet is about 2100 lbs., nearly 300 gallons, so 18,000 gallons per hour. Sounds improbable, so air/fuel mixture must be per weight rather than volume?
George B.

George, wow. At that rate I'd empty the gas tank in two minutes!!!!!!

The usual rule of thumb, for carbureted engines, is: if using a deadhead (i.e. non-return style) regulator, fuel flow in GPH = 0.43*HP, and if using a return-style regulator (theoretically the best way to do it by far, but a major PITA to implement), 0.27*HP (HP using flywheel figures). At least those are the formulas that are used in the racing fraternity.

What my circle-track racing friends seem to like to do is to use a big, high-flow fuel pump with a return system, to always keep plenty of cool fuel circulating, always there if you need it. Big, high-flow fuel pump + deadhead-style regulator is a recipe for an overheated, noisy, short-lived fuel pump. Plus dead head regulator springs bounce when the fuel is backed up and you suddenly mash the pedal to the floor, and so you can get a lag ... so to ensure smooth transition, they say to use the return system.

One of these days when I have a spare 20 hours I'll go for it ....!

Peter Burgess calculates it thus -

Max HP x 0.6 / 7.5

So if your 4.6 produces 250 bhp, it needs a pump capable of producing 20 gallons per hour (UK gallons)

So one producing 30 gph would give a good margin for any deterioation in performance of the pump over time.
Chris Betson

This thread was discussed between 24/01/2001 and 25/01/2001

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