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Old 05-12-2008, 22:43   #1 (permalink)
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Question 390 improved fuel economy

I have a 66 t bird and was wanting to know if there are any tricks, besides swapping to a 2 barrel, and better exhaust, to make my BB more friendly at the pump?
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Old 05-13-2008, 05:53   #2 (permalink)
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Re: 390 improved fuel economy

I have a 58 TBird with a 352. Hoping to improve the gas mileage, I have
focused on the ignition system as most vehicles had poor ones in those days.

I started with replacing the coil on mine (which appeared to be the same one as used on Model A's - mustard colored top). I got an MSD coil and
ballast resistor. This meant substantially better spark.

Next I widened the plug gap from .034 stock to .042".

On the highway, this got me up to 17 mpg, from 14.

Currently I have just installed solid copper core Accel plug wires so voltage is not lost in the wire. I intend to widen the gap further to .050" and see what happens.

The additional draw of the MSD coil takes its toll on the points and I may change to a solid state Pertronix or something.

My goal is to get 20 mpg out of it - highway.

You could ask whether the carb can be leaned out any. Back in '66 there was no incentive to have a clean running motor so it may be on the rich side. If the carb has metering rod(s) then you could experiment with different ones for little money and not much effort.

john - MA
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Old 05-13-2008, 12:28   #3 (permalink)
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Re: 390 improved fuel economy

I went with a MSD 6A ignition box for my mid 74 Chevy truck. What I like about that box is it will send mutiple sparks to the plug for 20 degree crank rotation for a complete fuel burn. That old 454 sure ran smoother & throttle response was alot better.

Can't use solid wires with it though.
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Old 05-13-2008, 18:04   #4 (permalink)
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Exclamation Re: 390 improved fuel economy

What they said. Something to consider too... for some reason Ford went from a 600 cfm carb to a 480 cfm carb on the 390 AND the 428 on the 1966 T-Bird. According to Pony Carburetors, a 4V 390 needs around 609 cfm for peak efficiency and driveability, while a 428 needs 668 cfm. But this is at 90% Volumetric Efficiency at 6000 rpm. It depends mostly on what RPM range you will be operating it. I'd consult Pony Carburetors on the matter. They specialize in Ford Carbs. Tell them what kind of car you have, if it's still got the original Ford 4100 carb, and what you'd like to do with it.
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Old 06-29-2008, 13:10   #5 (permalink)
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roll Re: 390 improved fuel economy

Hi, That all sounds reasonable. If you have a C6. Maybe a Gearvendors Over/under drive could help. It's a basic 2 speed transmission that replaces the tail shaft on the automatic. You end up with twice as many forward gears. Should make it above 20 MPG easily with your other improvements. The only down side is a shorter drive shaft is needed to make it work. Dave 69 Torino Talladega, 79 Ranchero Street rod
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Old 10-06-2008, 11:32   #6 (permalink)
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Re: 390 improved fuel economy

Update: I put Accel stranded metal core wires on, and widened the plug gap to .050". Driving at about 65mph on the highway I was able to get
20.2 mpg on a 210 mile drive. The plugs were new, I checked the timing and had the tires at 36 psi.

John


Quote:
Originally Posted by JohnG View Post
I have a 58 TBird with a 352. Hoping to improve the gas mileage, I have
focused on the ignition system as most vehicles had poor ones in those days.

I started with replacing the coil on mine (which appeared to be the same one as used on Model A's - mustard colored top). I got an MSD coil and
ballast resistor. This meant substantially better spark.

Next I widened the plug gap from .034 stock to .042".

On the highway, this got me up to 17 mpg, from 14.

Currently I have just installed solid copper core Accel plug wires so voltage is not lost in the wire. I intend to widen the gap further to .050" and see what happens.

The additional draw of the MSD coil takes its toll on the points and I may change to a solid state Pertronix or something.

My goal is to get 20 mpg out of it - highway.

You could ask whether the carb can be leaned out any. Back in '66 there was no incentive to have a clean running motor so it may be on the rich side. If the carb has metering rod(s) then you could experiment with different ones for little money and not much effort.

john - MA
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Old 10-08-2008, 01:42   #7 (permalink)
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Re: 390 improved fuel economy

Better exhaust and ignition are a given but your better off sticking with the four barrel carb, just stay out of the secondaries.
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