I have a 1976 F150 Ranger XLT it is currently all stock with a 300L6 and 4speed manual, 4x4

I am looking for advice to make it a better daily driver, currently has a single barrel carb

I have a daily commute of 45mi each way and would be 99% highway any advise to bump my current 7MPG up and get my cruising speed higher than 55MPH would be greatly appreciated

There is no budget, it's a family heirloom and I will put anything I need to into this truck

 

Before you do anything, do a compression test on all six cylinders to see what condition the engine is in mechanically.

Do you know what the axle ratios are?

 

Tire size and RPM at what speed.

I will say I think 7 MPG is pretty bad but are you also sure the numbers you used for the math are right?
Have you checked the Odom to mile posts to see if that is good or off?
How about the speed, checked with an app on your phone like say Google Maps?
If the speed is off the miles could be off also and then forget the math as that will not be right either.

Also I cant see installing a larger carb like a v2 or even a v4 helping the MPG as you are putting more gas in the motor that already gets poor MPG.

I built my 81 F100 4x2 flare side as a driver. 300 six, NP435 trans, 2.75 rear gear, 235 / 75 / 15 tires.
I kept the Carter v1 carb but installed EFI EXH manifolds and Y pipe as they flow better than the factory log EXH manifold.
I also went with 94 F150 EXH system (less cat) as the pipes are also larger than the 81 pipes for better flow.
I did go with a Thrush welded muffler and really like the EXH note.

Now because I want to drive the truck I also went with an Advance Adapter Range splitter over drive.
I did not see any change in MPG but it did lower the RPM so less wear on the motor.
The sweet spot is about 1800 RPM and that just happens to be where it is at in in direct drive at 55 MPH.
The speed limit here is 70 MPH and it over drive I am at the sweet spot of 1800 RPM.

I have re-curved the factory dist. and run 12* BTDC and ported vacuum advance. Forget what total timing is now.
Dose your vacuum advance work as that will help MPG.

BTW my trip to work is 40 miles each way and is about 95% high way but I take back roads on the way home and that is at 45 to 50 MPH with a few lights.
My MPG avg is 15 and have seen a high if 17 MPG. I also have a AFR gauge and it runs between 13.5 to 14.5 and sometimes into the 15.5 range.

Good luck on your quest and keep us posted
Dave ----

 

The stock 300 six responds well to one of the aftermarket aluminum intake manifolds and either a two barrel or small 4 barrel carburetor.
Most everyone switches to the 1987 and later EFI exhaust manifolds.
That will increase the cruising speed.

Add an air/fuel ratio meter to fine tune the carburetor for best gas mileage.

 

When I put my '65 F100 together with its 300 inline, my goal was reliability and fuel efficiency. Basically the motor is stock, but it does have a 240 head with smaller chambers for a bit of a bump in compression ratio.
The original plan was for a Offy intake with a 2 barrel. When I was shopping for parts, the manifolds were out of stock with an indefinite delivery date. Not only that, but the price nearly doubled, topping ot at over $700.
But Holley to the rescue. My son who works as an EFI tech at a hot rod VW shop, pointed me toward the Holley Sniper 1100, a single barrel version that bolts onto the stock intake.
So that along with mating a Tremec T5 trans to the motor, allowed 70 mph cruising RPM of about 1700.
Result? 22mpg highway, 13mpg in town.
I also put an insulating phenolic throttle body spacer with about an 8" square heat shield to keep exhaust heat off the throttle body. Ran fine without it. This was a done as a preventative measure to keep the TB electronics alive longer. However this resulted in an increase in stop & go fuel mileage from 11.5 to it's current 13mpg

 

Mike you are still using the factory log EXH manifold bolted to the intake?
I also take it it dose not get that cold where you are in CA or you dont drive it when really cold out?

I talked to a guy at a cars & coffee that had the Holley Sniper EFI on a 429 in a 68 Mustang and was having running issues because of heating of the EFI unit.
He also used a insulation plat to keep it cool and it fixed it.
It was this spacer and why I asked about it and the first I heard of heat & running issues with Snipers.

Spacer gave you better MPG? I wounder if I should give it a try
Dave ----

 

Hey Dave
I'm using the later EFI dual exhaust manifolds. No heat to the the intake. Here in Central California, the coldest I have ever experienced was 19°, but typically, 30s at night 40-50s during the day. Just need to let the ol' girl warm up a bit is all.

The thing to remember about a 429 in a 69 Mustang, is that it is a very big motor dimensionally, and a fairly small engine bay. It is about shock tower to shock tower. Not a lot of room for heat to escape. So, they heat soak.

Anyway, here is what I did. The photos are self explanatory. The spacer I made from 3/4" thick phenolic that I bought on Amazon
I took before and after temps of the throttle body and the throttle position sensor, which is out in the open, and saw a remarkable drop in temps.
Before...The "fuel bowl" was 160° / After, 118°
Before, the TPS was 175°. / After, 125°
The heat shield temps were between 135 and 150° with the coolest being the outer edges fore and aft. The hottest were, of course, directly above the exhaust manifolds.

 

Nice looking set up
Even with the EFI set up you still need to let it warm up some?
If so I wonder if it is because the air / fuel mix when it hits the cold intake the fuel drops out of the air?
The fuel would then dribble into the cly and act like a flooded motor.
That is one reason the intake is heated to keep the fuel in a vapor.

Because I use my truck in the winter to / from work of 40 miles each way and trash run on weekends is why I heat my intake with hot water and just deal with the heat soak and hot restart. Then again the truck sits all day when at work and at shows cooling off so dont have to much hot restart issues.

I hear you on the BB in the Mustang bay and heat trapped in.
I just never gave it a thought that heat would make the electronics on the EFI go bat sh** crazy.
Dave ----

 

I think what was MORE likely there was EMI/RFI causing issues and the phenolic spacer moving the air cleaner and computer up and away from the distributor was the behind-the-scenes fix. Ford engines in particular have this problem because of the distributor location relative to the Sniper.

I can't prove that, of course, and it doesn't matter since it did the trick for him...but aside from simple electronics failure from heat exposure, there's not much that would be causing issues from the heat (that I can think of anyway).

My car with the Sniper is a Windsor based engine. The wiring is...not my best work, let's put it that way. I was on a time crunch to get it running in time for a track event and it's pretty shoddy. I did put cheap ferrite core beads on EVERYTHING. Good plug wires. Things like that. I have yet to have any issues. Maybe I'm just lucky.

That looks fantastic! And great job doing some actual testing there. I was JUST thinking recently about making some kind of heat blocking plate for the Edelbrock 500cfm carb that is on my 300 I6. But I sort of convinced myself that it couldn't help ALL that much...eventually the heat in the engine bay would just be going around it anyway. I may reconsider my reconsideration.

I have TWO phenolic spacers (a 1/2" and a 1") and a total of three gaskets between it and the manifold and it still gets incredibly hot very quickly, even with the hood open. Like, can't bear to touch the throttle mechanism within a few minutes. I do have long tube stainless headers, which may contribute to that vs the factory cast iron manifolds.

If I do it, I might use an even larger piece, angled upward to block some of the heat coming off the radiator. It might also be neat to run a tube from the factory inlet that feeds off the front of the truck next to the radiator. Try to get some fresh, cooler air to the carb. But, for now, I'm in Arkansas and it's still hot outside, so I won't be touching that anytime soon lol.

 

For the reason you state, the intake is cold, and the vaporized fuel pools, is why I let 'er warm up a bit in the winter. What happens is it idles good right away, but coming up to the first couple of stops, when the engine returns to idle, the rpm drops some and the motor stumbles a bit. After a mile or so, its fine. By that time the intake is heated sufficiently. I also have the cold enrichment turned WAY down. Mostly in the interest of fuel economy. The default setting is way to fat for around here. And aside from that, most of my in-town trips are short, it doesn't get up to temp until about the time I get where I'm goin'!
But no troubles with hot restart....or any trouble whatsoever. I reckon I'm the opposite side of the fence from you. I'd rather have the ol' girl be a bit temperamental for the first mile or so, than dealing with hot start, or cookin' the electronics.
At any rate, I was having no troubles at all with the Sniper. But I had read over on the FordSix forum that some were having troubles because it was possible that the heat was messing with the units. What I did was just as a preventative measure....so my EFI would NOT go bat ***** crazy!

 

I for got in order to get the Carter hot air choke to work I took copper tubing and wrapped it around 1 of the EFI manifolds to pick up heat like the factory did thru the log manifold.
I found on a 20*f day the choke would still be on fast idle even after my 40 mile drive into work.
My fix was to use header wrap around the tubing and manifold to trap more heat and that did the trick.
That is right under the carb but I think the biggest thing adding heat to my carb is running hot water to the intake for winter driving.

In a year when I retire I can always bypass the intake heat as I wont be driving it to work and can let it warm up a bit more.
Dave ----