Fuel Economy 352 390

[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.