300 I6 vs. 351W MPG savings worth stock hp/tq trade off?

Econoryan

New member
In a 91 econoline say the 351w had a T5 trans. And the inline 6 w/ Np435. Both carbed.

Im having trouble deciding what motor to go with here, mostly a highway van.
 
Uh why not the T5 with the 300?

The OD will give the best milage. And allow deeper gears in the rear end. NP435 will tow anything and has granny low, but strict attention must be paid to the rear end ratio so you can still drive on the highway.

I have an NP435 in my bronco. Id love to be running 5.38 gears for the 37" tires, but I cant go any deeper than 4.56 gears. They put me at 3000 rpms at 70 mph. Not great for the highway but it works. 12mpg is my average. The good thing about running at 3000 rpms is that the throttle is barely open, sipping fuel. But its sipping 3000 times a minute... It also allows you to instantly be in passing mode with just a push of the skinny pedal.
 
Well the van i found is already setup 300 I6 w/ np435.

Thats damn good for 37's and 4:56's imo. This will be a 2wd highway cruiser. 29-31" tire. I'll have to test drive it on highway before i buy it.

I think ima go with this 6'er. depends how it runs on the highway. I do want a low 1st, that'll help with crawlin up stuff or just around parking lots slow.
 
Yes. FOR THE RIGHT CIRCUMSTANCE, ANY THING IS WORTH IT.

The ideal gearing for economy was cracked back in the 1950's but we had to wait till the late 1970's and early 1980's for the formula to be re-arranged for best miles per gallon for a given average cruise speed. It is based on the from the Index of Thermal Efficiency, found in French Grand Prix and English RAC litrature by Hodges,

and was revised in 1980 for the Australian Total Economy Run, to use the average frontal area and overall cdA drag factor for a late seventies, early 80's car. See http://www.snooksmotorsport.com.au/i...d=31&Itemid=39


All esle being equal, there is no difference in fuel economy between a 165 hp 300 I6 and 165 hp 351W if they are optimized induction and have the same kind of gearbox optimised. Same with a 500 hp turbo verses a 500 hp non turbo.

The Snook formula copies the age old French Index of Thermal Efficiency for optimizing 62 mph fuel economy.

The Dimensional analysis shows the inputs are here


"http://vb.foureyedpride.com/showthread.php?153148-4-2-V8-Info-and-pictures-needed/page2"

"https://fordsix.com/threads/gear-suggestions.76051/"

Coefficient Of Drag in Cd
Frontal Area Sq. Feet
Vehicle MPH = 62
Vehicle Weight (varies road load at 62 mph)
Tire Pressure (varies road load)
Brake Specific Fuel Consumption in US gal/hp-hr.
Drivetrain Horsepower loss AT 62 MPH
 
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