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By Chris S. - 14 Years Ago
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Hello,
This is my first post on these excellent forums,and I'd like to know the following-
What sort of gas mileage should I be getting from my 55 Fairlane ,(it has a '57 Merc 312 with a stock 4 barrel Holley,and a Fordamatic trans)?
It seems pretty thirsty!
Thanks in advance,
Chris.
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By junkyardjeff - 14 Years Ago
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Remember they were built in the days of cheap gas so they are not going to be anywhere close to modern cars,I would say 14 to 18 on the highway should be what they got.
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By Chris S. - 14 Years Ago
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Thanks Jeff.
I forgot to mention I'm in the UK where fuel is now about $7.50 for a US gallon.
I LOVE driving my '55,it's just very expensive to do so over here now.
Chris.
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By HT32BSX115 - 14 Years Ago
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I forgot to mention I'm in the UK where fuel is now about $7.50 for a US gallon.
That appears to be about right considering the exchange rate.........however the price also includes about a 170% tax on the wholesale price. I had no idea the taxes on motor fuel was so high in the UK! http://www.abd.org.uk/fuel_tax.htm
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By 56mercgal - 14 Years Ago
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Think that's why in the UK they would drive little Vauxhaul's and Morris Minors! Gas was high even in the 50's and 60's compared to the U.S.
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By junkyardjeff - 14 Years Ago
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With a little tweeking you might be able to get a little more mileage,add a electronic ignition and tune the carb some and see what you get. To be able to get different size jets for the carb you might have to go with a modern carb.
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By HT32BSX115 - 14 Years Ago
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Tweaking will do some......taller gears will make a large difference too.
You will want the engine turning around 2000 or less on the highway to get good mileage....
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By Hoosier Hurricane - 14 Years Ago
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Does the engine load up at idle, or is it very difficult to start when hot and has been sitting a while? If so, the power valve in the carb may be leaking. That will increase fuel consumption drastically.
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By Ted - 14 Years Ago
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You didn’t say what gearing but assuming 3.23’s or thereabouts and depending upon the wear in the engine then minimum expectations would be 13-15mpg for town driving and 15-18mpg on the highway. This is for a stock ’57 312 combination that’s in a reasonably good state of tune with a properly working mechanical and vacuum advance within the distributor. And that’s with todays U.S. gasoline. If you can find some gasoline that does not have alcohol in it, then fuel mileage will jump up another notch accordingly. John brings up a good point on the ’57 and up Holley power valves. Age tends to stiffen the diaphram in those and as a result, more vacuum is required to close them. There’s a point that they don’t close at all and the engines are running with the extra fuel being supplied all the time.
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By speedpro56 - 14 Years Ago
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I would also raise the timing from the ford specs of 6 degrees btc to 10 or 12 degrees btc if you have'nt done it yet with the vacuum advance disconnected. When done reconnect the vacuum advance and see if this helps gas miliage and power.
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By Chris S. - 14 Years Ago
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Thanks everyone for the replies.
The way the car uses fuel I reckon it must be the power valve which is at fault.
Can anyone advise me on how this is checked?
Thanks again in advance.
Chris
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By Ted - 14 Years Ago
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Chris S. (1/13/2011)
The way the car uses fuel I reckon it must be the power valve which is at fault.
Can anyone advise me on how this is checked?When removing the metering block to get access to the power valve, check the cavity behind it in the main body for wetness. If wet, then the diaphram is likely leaking or at the very least, fuel is being sucked from around the threads and past the gasket. A power valve tester comes in handy for checking the valve itself but that’s an item you don’t find in most tool boxes. Visually inspecting the power valve needle and seat for wear and trying to gauge the tightness of the rubber diaphram for aging would be next. If the power valve doesn’t work freely up and down or feels ‘stiff’ when working it, then replace it with a #65 power valve (6½”Hg opening). When in doubt, just replace the power valve and insure that the gasket seats squarely on the valve when re-tightening it into the metering block.
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By Chris S. - 14 Years Ago
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Thanks Ted for the information,that's very helpful.
Chris.
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