Fuel Economy 352 390

[410bruce]

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?

[hwoods]

when I had it in 1965--390 Galaxie 4:11 gears about 10 MPG

[frnkeore]

It depends on your weight, gears and foot, probably more than anything.

With 2.74 - 2.91, you could get as much as 18 mph (390), with a well tuned, low overlap engine, on the hwy. A little more with EFI.

Heavy accelerator pump use, brings it down, in town. Best mileage will be had using a vacuum gauge to know how to adjust your foot to get the best results.

Quench and chamber shape will help. The right A/F ratio combined with power valve setting, and especially EFI. One thing that will always help mileage, is a light car and high gears.

But, another way to look at it is, from the $ stand point. How much you spend, to get the highest mileage as opposed to how much the actual gas saved will cost. Money is money, weather it's spent in parts or gas. But, can you put a price on "fun"?

IMO, there is a lot to it, no matter what way you go.

[Gregg]

I have a '64 Galaxie with a 390, slightly upgraded cam, factory shorty cast iron headers, 2.5" exhaust, Magnaflow mufflers, C-6 with the lower 1st and second gear from a AOD, and 3.00 open rear gear.  Around town I get about 9 mpg.  I do like the sound so that includes a lot of WOT so I can chirp the rear tire on the 1 - 2 upshift.

[chilly460]

I rarely check it, but when I do I’m getting 17mpg highway with 4.10s and a Tremec 500.  Cam is 224/232 9.2:1 CR. 

[My427stang]

I ran my 71 F100 for years as a daily driver, .030 390, 9:1, 270H, Street Dominator, 600 Holley, headers, recurved distributor, 4 speed, 4x4, 3.70 gears, 33 inch tall tires.  Ran at 12.5 around town and 14.5 on a long run, ran great but wasn't knife-edge tuned back in the day. 

As Frank said lots of inputs, but, keep overlap low, compression high, mixture on the lean side for mileage. Tight quench helps the the lean mixture not ping, and then it's all how you drive it

My Mustang (4.89 EFI 4.11, TKO-600) gets about 15 on a good Nebraska back road trip, but I also tend to horse it now and then. It does well due to the gearing and EFI, certainly not built for mileage

[410bruce]

I'm impressed with the higher mileage you guys have posted, especially with the mods and heavy vehicles mentioned.
It stands to reason that if you're heavy footed the mileage will suffer but it sounds like if you drive around normal and like an old man, (at 55 I'm kinda there  ) 390s are capable of pretty respectable fuel economy.

Now, if you were to replace the 390 with a 352 in the above examples, would mileage go up or down?

[My427stang]

I'm impressed with the higher mileage you guys have posted, especially with the mods and heavy vehicles mentioned.
It stands to reason that if you're heavy footed the mileage will suffer but it sounds like if you drive around normal and like an old man, (at 55 I'm kinda there  ) 390s are capable of pretty respectable fuel economy.

Now, if you were to replace the 390 with a 352 in the above examples, would mileage go up or down?

In theory, up, but it depends how hard you had to work it to do the same job

[410bruce]

I'm impressed with the higher mileage you guys have posted, especially with the mods and heavy vehicles mentioned.
It stands to reason that if you're heavy footed the mileage will suffer but it sounds like if you drive around normal and like an old man, (at 55 I'm kinda there  ) 390s are capable of pretty respectable fuel economy.

Now, if you were to replace the 390 with a 352 in the above examples, would mileage go up or down?

In theory, up, but it depends how hard you had to work it to do the same job

Kind of what I was thinking as well, Ross.

Hoping some 352 guys will chime in here.

[Gaugster]

I was in the 9mph range even with a 2.75:1 out back but with lots of inefficiencies. C6 was slipping and barely made it through the season. Engines a little on the tired side. If my upgrade to the 6 speed auto goes well the fuel economy should improve some. Not hoping for miracles however. Just a higher cruising speed and more power handling. Current it's a 390 with an "RV" cam, Performer RPM, QF 680 cfm and an MSD ignition.

[frnkeore]

I had a '60 Ford, with a 300 hp, 352 with 3.54 gears and Cruise-O-Matic trans (4k lb car).  After I got drafted, in '65, I had to drive it to Fort Hood, TX, from SoCal. At 70+, I got about 16 mpg.

Now, if your talking PU, your hwy mileage will suffer, suffer even more with 4X4. I'd say take 1-2 MPG off for each, if you drive 70 mph.

[Royce]

I had a 74 F-350 with a car hauler ramp bed and a 360 4peed. 2bbl Autolite Fresh valve job small RV cam, 4:11 tall tires headers. Empty 13 maybe a 14 in there  Loaded.... 6-8

[shady]

'63 gal stone stock 352 auto 300 gears gets 12. No matter how I drive it. I think it should do better but...

[BB-63]

1963 Galaxie 390/C6 & 3:1 rear was 8mpg around town and 12mpg on the highway.  I think the C6 made it more thirsty than it should have been. 

[frnkeore]

The car I had, before the '60 Ford, was a '58 Edsel Corsair (heavy car, Merc Chassis, boxy, probably 4300), with a 410 MEL, it was a push button Cruise-O and had 2.91 gears. It got a  measured 16 mpg, on the fwy. I was really surprised. Maybe it was the leaded 100+ octane gas we had in those days

12+/1 CR was more the norm, back in the 60's and 70's for street or race builds.

[FrozenMerc]

My '62 Merc Monterey Wagon gets 18 mpg consistently on the highway and 15 mpg around town. 

352, 0.030" over.
Edelbrock heads and Intake
9.5:1 compression
600 cfm Holley
Elgin 966P cam
FPA shorty headers.
Broader AOD trans
3.6:1 9" rear.

I think it could be improved a bit by switching to a cold air intake.  Definitely leaving some power and efficiency on the table by sucking in the hot / less dense under-hood air.

If the wagon was an apple, my '76 F250 Camper Special would be the orange.  10 mpg no matter what you did with it.  I think a good overdrive would've helped this one out a bunch.

390, 0.030" over
Ford Iron Heads and Intake
9:1 Compression
Holley 600
Howards dual pattern cam.
Long Tube Headers.
C6 Trans
4.11:1 Dana 60 rear

[RJP]

My example is not a 352 or 390 but a 428 +.030" in a 66 Galaxie LTD, C6 and a 2.75 gear. The best I've done is 17.35 mpg going from Bishop Ca. to Hayward, Ca via hiway 120 thru Yosemite. a fairly evenly split between highway and mountain driving. Driving conservatively [65-70 mph- highway] yield best mpg. Trip is app. 295 miles, topped off the tank in Bishop and the car took 17 gal. when the gas handle clicked off at the gas stop in Hayward. My 66 Fairlane 390/GTA, C6, 3.00 gear will average about the same [16.8-17.2] freeway driving. Around town...Not so good for both of them.

[frnkeore]

Bishop to Hayward is mostly down hill, isn't it?

[TJ]

I've had a factory 352, slightly modified 390, and now a 482 all in the same truck with same gears and having driven the same 170 mile round trip many times with each.  All three were/are around 13 mph when driven the same way (ie with a light foot) on this round trip.

Factors I believe improved mpg despite the increase in cubes across the three FE's I've run:  intake choice, headers, compression ratio, rings, and roller cam (allows use of modern oil).

Surprisingly, adding a gear vendor overdrive behind the 482 had a fairly small (if any) effect.

IMO, in town and heavy footed driving hurts mpg more on a big cube engine than on a much smaller engine.   

[plovett]

Surprisingly, adding a gear vendor overdrive behind the 482 had a fairly small (if any) effect.

That is interesting.   Can you tell me what rear gear and tire size you had?  Was it a manual or automatic?

thanks,

pl

[TJ]

Surprisingly, adding a gear vendor overdrive behind the 482 had a fairly small (if any) effect.

That is interesting.   Can you tell me what rear gear and tire size you had?  Was it a manual or automatic?

thanks,

pl

I have a 4.10 rear and tire size is 235/85/R16.  Tranny is 4 speed (NP435).  I really like the gear vendor because it slows down the rpms and makes the freeway drive much more relaxing.  Since the gear vendor is 0.78 ratio, I was hoping for 1-2 more mpg....somewhere into the 14's. 

I'm scratching my head...overdrive should have increased mpg.

Here's my one wild guess...perhaps someone can comment.  My cam puts my peak torque at 3700 rpms (based on dyno results).  The gear vendor drops my rpms from 3000ish rpms at around 68 mph to 2300ish.  Maybe my cam is more efficient when engine is running closer to 3700 where it has peak torque?  If I had a cam that made peak torque at say 2600 rpms, I might make it into the 14's for mpg?

[plovett]

Surprisingly, adding a gear vendor overdrive behind the 482 had a fairly small (if any) effect.

That is interesting.   Can you tell me what rear gear and tire size you had?  Was it a manual or automatic?

thanks,

pl

I have a 4.10 rear and tire size is 235/85/R16.  Tranny is 4 speed (NP435).  I really like the gear vendor because it slows down the rpms and makes the freeway drive much more relaxing.  Since the gear vendor is 0.78 ratio, I was hoping for 1-2 more mpg....somewhere into the 14's. 

I'm scratching my head...overdrive should have increased mpg.

Here's my one wild guess...perhaps someone can comment.  My cam puts my peak torque at 3700 rpms (based on dyno results).  The gear vendor drops my rpms from 3000ish rpms at around 68 mph to 2300ish.  Maybe my cam is more efficient when engine is running closer to 3700 where it has peak torque?  If I had a cam that made peak torque at say 2600 rpms, I might make it into the 14's for mpg?

I was thinking along the same lines.   That's why I asked about your gearing and tire size.  I was wondering if the overdrive dropped the rpms too much for best fuel economy.  Those are tall tires, even with 4.10's.   A typical car combo with a 27" tire would need a 3.50 gear to have about the same rpms as your combo.   I think you are on the right track as to why the mpg didn't improve.   I am sure it is still nice to have the rpms lower even without an mpg gain.  I don't think peak torque is always exactly where best fuel economy occurs.   I bet it is a factor, but not the only one.   Maybe a lower rear gear that would put your cruise rpm in between your current 4th gear and your 4th gear overdrive would be the ticket?  Like a 4.30 or 4.56 rear gear?

I dunno for sure.  It is interesting though.   

Also, carburetors sometimes have trouble metering fuel well at very low rpm and low throttle cruise conditions.   I'm assuming yours is carb'd?   I love carburetors, but very low rpm and low throttle is a place where fuel injection shines, in my opinion.  Annular boosters might help for a carb. 

pl

[RJP]

Bishop to Hayward is mostly down hill, isn't it?

Ever drive it...?

[The Real McCoy]

I guess I'll throw my 2 cents in here....

63 Galaxie
428 CJ Stroker (462)
C3AE C 406 heads with CJ Valves
63 R Code  2 x 4 Intake with 750 Quick Fuel Carbs
Comp 280H cam
63 R Code cast iron headers
TKO 600 transmission with .64 overdrive
3.00:1 rear end.

Best MPG is 19.7 at 65-70 on 4 lane freeway on a 220 mile trip.
Average MPG is 16.0 over 6221 miles.

It does get a little jerky in 3rd and 4th gear running around town but not to the point it's hard to drive and no need in trying to put it in 5th gear under 60 miles an hour.  80 MPH is right at 2000 RPM

I am thinking I should put the original 3.50:1 gears back in it just to see if how much the driveability improves but I really don't mind the way it is now.  I might even pickup some MPG with the 3.50:1 gears. 

[410bruce]

Wow guys, your responses are all very interesting and informative. Keep them coming, regardless of cubic inch.

[winr1]

Stock 65 F100 with 352- 2 barrel, 3 on the tree, 3.50 gears and L78 tires on the rear ... 15 mpg .. normal drivin

Changed cam and rear gears since, hve not checked mileage



Ricky.

[chilly460]

I guess I'll throw my 2 cents in here....

63 Galaxie
428 CJ Stroker (462)
C3AE C 406 heads with CJ Valves
63 R Code  2 x 4 Intake with 750 Quick Fuel Carbs
Comp 280H cam
63 R Code cast iron headers
TKO 600 transmission with .64 overdrive
3.00:1 rear end.

Best MPG is 19.7 at 65-70 on 4 lane freeway on a 220 mile trip.
Average MPG is 16.0 over 6221 miles.

It does get a little jerky in 3rd and 4th gear running around town but not to the point it's hard to drive and no need in trying to put it in 5th gear under 60 miles an hour.  80 MPH is right at 2000 RPM

I am thinking I should put the original 3.50:1 gears back in it just to see if how much the driveability improves but I really don't mind the way it is now.  I might even pickup some MPG with the 3.50:1 gears.

That's some LONNGGG gears with the O/D, calculate it as 87mph to turn 2000rpm with a 28" tire. 

[The Real McCoy]

Tire size is 215/70R x 15 which is 26.85 diameter. “Tremec Toolbox “ calculates to 83MPH @ 2000 RPM. The mentioned 80 MPH @ 2000 RPM are off the speedometer and tachometer, close but probably not exact.

[frnkeore]

Bishop to Hayward is mostly down hill, isn't it?

Ever drive it...?

I was born and raised in CA. I haven't taken 120 but, I have spent a lot of time in and around the Bishop area. I use to go to a cabin at South Lake and fishing at Lake Sabrina , plus hunting in Owens Valley area.

Bishop is 4000+, you do have to go over a almost 10,000 ft summit, going that way but, Hayward is close to sea level so, it's down hill.

[RJP]

Bishop to Hayward is mostly down hill, isn't it?

Ever drive it...?

I was born and raised in CA. I haven't taken 120 but, I have spent a lot of time in and around the Bishop area. I use to go to a cabin at South Lake and fishing at Lake Sabrina , plus hunting in Owens Valley area.

Bishop is 4000+, you do have to go over a almost 10,000 ft summit, going that way but, Hayward is close to sea level so, it's down hill.

Since you are so interested in the geology of my travels you might find it interesting that the trip to Bishop from Hayward yielded 15.5 mpg. Not too bad for a 4200 lb vehicle [not including 2 people, luggage, tools, cooler, etc.] going up hill. 

[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