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What are the best methods to get the fuel consumption down on a 390? Best bet is removing the current Holley carb, I guess, another probably resizing the jets. Any other good idea?
Need to know this for a fellow club member.
 
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Drive a Escort! LOL.
I have heard resizing jets helps but To much really affects driveablilty.
good luck
surveyboy

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Yeah I got the same problem. I'm sure my Holley is a mess and the engine probably needs a tune-up. Oh well. What's money when you're in heavy debt????
I coast up to intersections and only step on it occassionally eh,eh,eh.........

Michael G.
 

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Anything you can do to increase efficiency like better exhaust, lower weight (aluminum intake and heads), good tune-up. Reduce the rear final drive ratio such as put in some 2.30 gears instead of the lower std gears.

The Holley won't be a problem unless it is out of tune. Biggest fuel economy improve: don't get into the pedal :)
If the Holley already is jetted correctly reducing jet size will affect drivability and could hurt the engine by being too lean.

The very best way to improve a 390 is drive the Escort as mentioned earlier :)

Paul
1965 Mustang 2+2
1989 Mustang GT Convertible
MCA #27261
MCA certified judge for 65's and late models
 

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Maybe your looking at the wrong end of the car. Whats your rear gear ratio?


MotorHead

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Turn the engine off at the top of long hills.../forums/images/icons/smile.gif. You may get better mileage with a better electronic ignition also, but best will be with manual transmission and rear end gear ratio swap.

69 Sportsroof, 351C, 4spd toploader, Restomod BOSS 429 clone - the one and only (?) 1969 BOSS 351

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I've heard that running only "unleaded foot" in a 390 will improve mileage a lot! ;) Dickson

1965 GT fastback / "Fastbasketcase" (by Midlife)
There's a fine line between "hobby" and "mental illness" - Dave Barry
 
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I estimate to be getting around 10mpg city and 13mpg hwy (US gal) with the stock 390 Mach 1, 3.25 axle, auto. The '91 5.0 , gets about 14mpg city and 24mpg hwy, 3.27 axle, AOD. This is because of the auto overdrive tranny. If most of your miles are hwy then installing an overdrive would probably be the best way to go, if not then the next best thing is to use a 2.5 rear axle. You wouldn't want to reduce it so much though that your stuck in second around town. Like other posters have said, performance mods and a well tuned engine will also help. You can't really lean out the engine a lot though as it can cause damage. Also if it's going to cost $3000 to do the mods your going to have to drive a lot to get the savings back so maybe it's not worth it. Just my 2 cents....

Adrien.

65 GT Coupe, dismantled waiting for resto.
67 Restomod Coupe, in assy.
69 Mach 1 S code, SWMBO say don't take it apart!
91 5.0 LX HB, driver.
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