I had a Mustang with a 5.0 best it would do was 25mpg I now have one with a 4.6 and it makes 25mpg
I wouldn't get My hopes up.

 

Installing A 1987-93 Mustang SEFI 5 Liter V8/AOD Drive Train into A '61- 79 F100 - F250 Truck .: Articles
Look at this thread. This guy says that a EFI 5.0 coupled to a AOD with 3.70 rear gears gets a comined 18 - 20 mpg. This is the set up I plan on installing in my 78 late next spring, as well as doing the CV frontend swap

 

thanks ill read through it.

 

The key is really the tranny and rear end gearing. A properly sized and properly tuned carb can realize the same efficiencies as EFI. Car craft or hot rod magazine just proved that. EFI will do a little better (consistent) but the main thing with EFI is the ease of starting when it is cold. As far as mpg gains, an over drive tranny will give you the best bang for the buck. I have read of huge increases in mpg's when people switched to an AOD.

I currently run a 302 with a c-6 and 3.00 gear. It is my daily driver. When I first got the truck it had a 600 cfm Holly carb on it that ran horrible. I believe for DD use a eldelbrock carb is the way to go so I switched. It made a HUGE difference in the driveabilty. It doesn't bog down and the throttle response is perfect at all RPM's. I don't really keep track of MPG'g but I can tell you this one goes way farther than the bad Holley. I also went to a taller tire in the rear. Swithed to a digital MSD and blaster 3 coil as well but I couldn't tell you if it made a difference on the MPG? My next step is an AOD tranny. When I do it I am going to do a detailed thread on the swap; I have not seen one yet so I figure it could help some people.

 

my dad got 22mpg with our 71.
351C 2bbl with a c4. driving from phoenix to alberquerque with a 1500lb load.
so yes its very possible.
when i get the truck for my graduation present, im gonna build it, adding an overdrive, edel intake and carb, K&N airfilter, bigger dual exhaust, and narrower (245/75r16) bfg commercial tires, and without that payload. so im expecting at absolute LEAST 25mpg.

 

I really wish one of these World class Mechanics that can take a 10 to 13mpg truck
and turn it into a 20mpg gas sipping wonder wagon had a shop.
I and every old truck loving American would be standing outside His door waiting
The new eco boost trucks just makes that.
No a carbureted engine can not make the same power at a low rpm that a EFI can.
That's why You didn't see cars and trucks running 1600rpm at 60mhp with a carburetor
It's all been tried
Yes 16mpg in a F100 is easy 18mpg with a small engine on flat ground maybe and I'm talking at 60mph.
20mpg and higher Your doing what People have been trying to do for last 40yr's
And if You do get it done just remember what happened to the Guy that built the
50mpg carburetor LOL

 

Do you have a running engine now or are you staring at an empty engine bay? You can spend a lot of money to avoid more at the pump.

If you have an existing, running engine in good condition you can do a lot of small things to improve mileage. Any of these will also apply to a potential engine build. Learn to accurately tune a carb, regardless of brand. They are far more adjustble than idle speed, idle mixture and jets. I've done a lot with bothe Holleys and Edelbrocks. My preference is a Holley, but any carb is going to take some work to get just right for YOUR engine. Straight out of the box, an Edelbrock is typically closer to ideal. Also don't be araid of timing. I like to have about 34-38 degrees of mechanical timing, all in by 2500-3000 rpm, which will typically leave base timing about 20 degrees, plus another 10-12 degrees from the vacuum advance. Vacuum advance needs to be hooked to MANIFOLD vacuum, not ported. More initial timing means more vacuum, smaller throttle opening and better driveablity and mileage. Another big thing to do is slow down. These trucks have the aerodynamics of a brick. I've found any time I'm doing mileage testing if I slow down from 70 to 65 on the highway, it's always worth some mpg. Run your tires near max pressure spec.

If you're going to build an engine don't be afraid of compression. Compression builds torque and makes an engine more efficient. FE motors, 360s in particular are bad for leaving the pistons way down in the hole. For something you're just using as a driver, not towing or using for work, a smaller engine will by nature have smaller displacement per cylinder and use less fuel. A 302 is probably one of the better options if that's the case. A 300 six in theory would be similar, but honestly they are not an efficient design and are likely to use MORE fuel than a 302, although it will have more torque.

Devin

 

Just have a complete 72 roller. no motor.

 

If a manual trans (whether 4 or 5 speed) suits your needs, it's a good help with economy.

I've had both an AOD & a C6 in my F250 - I didn't use O/D in the AOD because of our 60mph limit & hills, but both transmissions gave the same mpg & power losses as each other.
I'm swapping the C6 for a manual in a couple of weeks.

While I haven't owned one, the consistently best mpg figures (& long life) seem to come from 300 six cyl. trucks, especially 2wd, manual trans., with the right gearing for their application & tire size.

 

Many times when we go swapping parts around and re-connect to existing we get wrong readings. The speedo gear was left in the tranny and doesn't match the rear ratio that it once did. I have seen this many times. Someone does a swap like your dad, gets incorrect readings, sees a big false reading, gets an erection and starts spreading the good news.

Bub, I aint calling your dad out, but it didn't happen. a 2 barrel C hooked to a C4 is not an overdrive, is in a flying brick bat with no earo.

Get the engine warmed up, hook up 1 gallon of gas and drive it until it runs out then measure the run. It wont see 15 miles. I have been around them since they were new, trucks do not get that kind of mpgs with carbed setups.




John

 

It is a simple matter of physics. A 2 ton truck built like a brick is not going to get great gas mileage. I am buying a '70 with the 300 six, and 4 speed manual trans, because I believe it is the best combination for good gas mileage. I do plan on using it as a daily driver, but it will not tow or haul anything extremely heavy, as I will be buying a F-250 4x4 for that. So I can concentrate on mpg with it. I plan on upgrading the 6 with headers, cam, and intake manifold/Weber carb (All from Clifford Performance) and if I can reach the 20mpg mark I will be extremely happy, but I seriously doubt it will happen. Especially since the truck I am buying is currently a flareside. It doesn't have the smooth sided bed like the styleside. I plan on swapping it for a styleside. I also plan on doing the IFS/IRS swap that elgemcdlf did to his. Not for better mpg, but better handling. However, lowering the truck will help mpg, although it will probably be negligible. Making the truck lighter will help. For every 400 pounds you remove, you gain 1 mpg. However, unless you have a bed load of scrap iron, I doubt you can safely remove 400 pounds from your truck. Aluminum wheels will help, also an aluminum intake, and headers. Don't forget though that all these items cost money. If you spend thousands of dollars on your truck to improve mpg, and gain maybe 20%. Then depending on how many miles you drive, it make take you several years to recoup your losses.

Buy a vacuum gauge, and drive like a granny, keeping the needle as high as possible, and you will increase your mpg. However like Kevin stated, there are a lot of things that affect mpg. Stop and go traffic, hills, jack rabbit starts etc, but in the end you are still dealing with a two ton brick.

 

Most new trucks get no where near 20mpg. It's gonna cost you a lot to save a little gas. Now, that diesel buildup sure looks nice, but not real easy for the average guy. I have a 85 f150, 5.0, AOD, 3.55 gears. The OD shifts in a little late, but 16.5mpg is about the best I've been getting lately. That's on a 22 mile one way DD with NO ethanol in the tank and very little traffic to mess me up and gently rolling hills. Traffic lights, erratic drivers in front of you, etc. will decrease your mileage.

 

well he did say he had it leaned out.... but seriously, i myself have witnessed this truck getting about 18mpg with a camper on it driving in the mountains.
guys, i know this sounds impossible, but this truck must be one of the flukes, cuz its true. Scouts honor.

 

I'm with Jowalker. Get on an interstate, use the mile markers and see what you odometer says compared to 10 (or even better 20) mile markers. I'll bet yours is way off.

I have a 2011 Fusion that consistently gets less than the mpg shown in the "driver info center". Check it with a pencil and paper and on a measured 100 miles and I might have an easier time believing you.

 

All true except the 300 Six has a ton of torque so towing and hauling shouldn't be as much of a problem as you would think. In fact with torque EVERYWHERE in the RPM band, it will often tow better than the 302.