Fuel Economy 352 390

[frnkeore]

I would say that's very good.

The area from Bridgeport to Lone Pine, was my play ground, when I lived in SoCal. That is one of the reason I moved first to Yreka, in '76 (20 mi S of OR border), then to Oregon 10 years later so, I could have a environment like that.

I do have a lot of mileage data, from my '71 Ford F100. 240-6, 3.70 gears, 31" tires, on all fours. It weights about 4k. It only got 16 mpg @ 65 (back in the days of "stay alive at 55"), about the same, in town. That's over two 4000 ft passes, a very long one out of Redding, CA. It would only do 85-90 mph and got 10 mpg, at that speed. I got 2 tickets on one trip, in about '79. Those big 11x15 Tru-Trac's, hurt mileage and speed.

My '73 F150, Extra Cab, weight 5800, it has a 400 in it, with a small RV cam, headers and a Edel & 715 Holley. I don't know what gears it has but, it got 10.5 x 15's, all around. I did a 1 mo, 5 days a week, 144 mi round trip drive (sub contracting) over three 2000 ft, passes and averaged 14 mpg. 10, in town.

[TimeWarpF100]

Just curious, what are you guys with warmed up 390s or 352s getting for fuel mileage? Warmed up meaning a basic strong street runner--4v, mild camshaft, headers etc.
Is there a big difference between 390 and 352 mileage, all else being equal?

My bone stock 1966 F100 Ranger gets 22+ mpg if I keep speed 65 or under. It has a bone stock 352 3spd column shift with factory overdrive and a 3.25 rear gear. Pretty much same truck with a 3.5 gear 3spd column but OD not working yet gets 14.5 to 15 mpg but a 4v intake with Holley carb has been added. ALso notice a 3+ mpg loss on other truck going from factory 2v to a holley 2v. (4412)  Typical 352 automatic usually 10-12 4.10 gear tall tire while the 3.5 auto in proper tune around 14.

I am currently building a 390 more for low rpm cruising for yet another '66. It will have 3.50 gearing a '66 GT390 carb from Drew and a GV OD. All the proper machine work to bottom end with a custom piston, good ring pack, zero deck 9.0 comp and mild cam, 406 Shorty headers and just heard from machine shop machine work should be complete this week. Will soon find out what it gets in comparison to the 352's. Will be very disappointed if it does not get at least mid teens or better. Oh yeah a tight custom converter too.

[TomP]

Depends on your foot more than anything. My 428 ramp truck carrying my Fairlane got better mileage than my friends stock 5.0L Fox Mustang. He spent more on gas on the same trip to Bremerton as i did. Until i drove his car his best mileage was 17 miles per imperial gallon. On the long trip to Las Vegas i got 33 mph my turn of driving his Mustang at more than double the speeds he was driving. He was driving no more than 60mph even in 70 mph zones. He drove like the gas and brake pedals were on--off switches. He's either hard on the gas or hard on the brakes, no such thing as coasting. Kind of terrifying to ride as as a passenger when someone is accelerating up to a red light then hammers the brakes. He could wear out a set of brake pads in a couple months with mostly highway driving. I think it'd take me five years to do the same.


Load and vaccum matter more than speed or RPM.  Most little four banger pisspots have little or no overdrive and steep gears. 4000rpm at 10% throttle opening will always get better mileage than 1600 rpm at half throttle.

[cammerfe]

As a comparison, in the Spring of '64, two buddies and I went from Metro Detroit to Sebring, Florida for the 12 Hour Race. We drove my almost new (delivered in February) '64 Custom/427. The car came with a 4.11 rear end, and, for the trip, I swapped in a 3.50. The car came with 6.70X15s, and I put a set of 8.10X15s on the back as well.

The warranty was 90 days or 3000 miles, and in those days, before I-75 was finished, a good part of the trip was on one-lane-each-way highway, so I pulled the little plastic gear off the end of the speedo cable and then plugged the cable back into the trans. I made up a little chart of engine RPMs matched to 4th gear speeds and taped it to the dash. The trip was over a long weekend and the odometer didn't change at all.

We agreed that we were going to drive straight through. We'd get food when we stopped for gas, and change drivers on that same sort of schedule. On the sections where we could actually use open stretches of I-75, we'd try to stay above 100 MPH as much as possible. We averaged 11.7 MPG for the entire trip and had one tankful where we calculated at a 'dead-nuts' 16 MPG. We didn't use the same roads going and coming, and as I recall, it was something better than 1200 miles one way and approaching 1400 the other way.

KS