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Old 03-06-2005, 03:08 PM
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Fuel Economy/Tuning - Olds 455

Hi Folks,
Being that I am new to carburated vehicles, I was wondering what kind of gas mileage I should expect from my '72 cutlass.

It has a mildly worked over 455, Hooker Comp Headers, Edel. Performer manifold, Accel HEI distributor, Edel. 750 carb, and unknown mild cam. It is a '73 J-head motor and the trans is a built TH-375 with a 1500 (stock) converter. The rear end is a 3.08 open.

I get around 9-10 mpg city and 12-14 freeway. Is this what I should expect? It is tolerable to me, but the carb seems to have a mild off-idle flat spot, and a pause before the secondaries come in if I whomp on it. It lays about 30 feet of rubber ON DEMAND though, which I am quite satisfied with.

Any ideas to better tuning? Timing recommendations? Perhaps a metering rod replacement?

Since I will be modifying the motor later, I am leaving everything as is. Later upgrades will be forged pistons, mondello intake, and Edel. Aluminum heads.

Thanks for your input,


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Old 03-06-2005, 03:32 PM
4 Jaw Chuck's Avatar
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Sounds pretty good to me, might want to fine tune the idle mixture with a vacuum gauge...might help the off idle lean spot.
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”

— Han Solo
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Old 03-06-2005, 03:50 PM
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....well I'd say that is not bad considering you're talking a usa gallon, up here in canada the imperial gallon would give you about 20% more in milage which would make it 15-17 highway , so you are about right with today's crappy fuel. Could try bump up the timing a couple of degrees and see it don't ping, may give you a hair more distance.
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