I'll start off by saying that, yes, I know I shouldn't expect high mpg's out of a greasy farm truck with a 351M. BUT, I may as well dabble in some fuel saving methods. Once I get the truck running I will begin the list of testing. Some methods may or may not be tried but I will still mention them.
Method No. 1: The single lawn mower carb

I chose this carb in particular because it's the same one that's on my John Deere 116 riding mower, and after looking at the carb I realized it wouldn't be too hard to adapt this one to a Ford engine. I should also mention that my idea came from this video by Thunderhead289 ( ). Now this specific carb is a downdraft, which means that theoretically I should just be able to cut out a metal plate and use it as an adapter. Another benefit is I can use the stock air cleaner so nobody can see the shame.

Method No. 2: Asthma Medicine

This is a lot simpler to do if I do end up feeling like pulling the motor, but it's essentially just porting out the head, getting a better intake, and I can't believe I'm saying this, adding headers just to make the engine more efficient. I feel the results from this would be minimal.

Method No. 3: The toggleable 4 barrel.

Same Idea as the lawn mower carb, but have four smaller side intake carbs (welded to a plate similarly to the single carb), but the one has it's own independent choke. I can choke off the three other carbs during normal use, allowing for good mpg's and dubious power, but for when I want to destroy some bias plies, I can pull a cable and essentially give myself a four-barrel carb. Would it work? I dunno

 

Sounds like a fun experiment


I will say I feel the 1 Barrell John Deere carb may not supply enough air after a certain point. Starving the engine of air and fuel. For low rpm I don't see any reason why it would not work. Once the Intake demands of the engine exceed what the carb can give. It will fall on its face and potentially cause damage in form of heat from lean condition.

With a vac secondary 4 Barrell if you keep you foot out of it and lower rpm the secondaries will never open.

Tuning a carb to run efficient even if its a 4 Barrell should be about as efficient as you can get.

The best money you can spend is for a wideband O2 sensor and guage to monitor air fuel ratio and adjust carb.

Jet changes etc you can even make a.4 Barrell too small for a 351m fuel wise..,the cfm airflow will be there but not enough fuel jets too small.

 

The difference between the JD small carb and and v4 carb is the amount of air each will let into the motor.
The small JD carb would be like NASCAR dose when they run restrictor plates to keep the speed down they do not make it run lean.
The v4 carb will allow a lot more air into the motor and as was pointed out can lean it out, jets, to the point it can hurt the motor.

I also for running a AFR meter so you know just what each fuel metering unit is doing.
I run one on my 81 F100 with a 300 six and v1 carb. I am seeing I can lean it out a little to hope get a little better MPG as I am in the 15 MPG range with a best of 17 MPG.
Dave ----

 

That's a.very good example and I bet you prob right.

The worry wart part of me would be afraid at max CFM thru the carb that due to design it may not supply enough fuel to match the airflow intake the 351 is demanding. Now jetting that JD carb to compensate is definitely possible to correct the issue. If such parts are available. Or modify the existing.

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you are right about all these thoughts, but 77 hos is ultimately right... these should not be any more fuel efficient than a properly tuned 4 barrel carb. it would just be like if you adjusted your throttle cable in a way that restricted how far the property tuned 4 barrel could open. restricting air is ultimately restricting both air and fuel which is restricting HP which is why restrictor plates lower top speed... they restrict the HP to exceed the air and rolling resistance they are experiencing going around the track. I want to know if you can run a 351 on a single barrel JD carb so please do it, but what you are ultimately doing in restricting air and fuel, is restricting the amount of HP the engine can produce and restricting it in this way will result in better fuel mileage and it will similar to a floor mat getting stuck under the gas peddle and preventing how far you can open the throttle with your current carb set up.

 

A friend told me a story his father had told him of the farmer that lived down the road. Promised his son a new truck if he graduated high school. The son did and wanted a new Chevy. Was in the early 50's, his father bought after the graduation. The truck ran fine but was so slow, the son drove it for years and then pulled the engine to replace it with another. Found a thin plate below the carb with a hole the size of a dime. The father had the dealer do it to keep the son safe in younger years. Same effect as the old large truck governors.

 

I'll be looking back.

Back in 1991 just before we started building our log home but after buying land, well, etc .... we knew was gonna be a long build, so we took a long camping trip. I was trying timing changes and gradually l leaned out the Holley 600 cfm carb on my 351M with camper shell and gear. Mostly flat land, small hils, beach. I got it up to 16 between fuel stops, but a few weeks or so later, burned a couple valves. I reverted to original jetting then.

 

There are some youtube videos where someone with a beat up maverick did it with a motorcycle or lawn mower carb. I started to do something similar, years ago, with a dual system. We made a heat exchanger to heat the gas before it went through an Impco propane carb, that sat on top of the regular carb. It worked, but we had some problems making parts, (and being starving students). A later model runs the air and fuel through a heat exchanger, that then goes into the manifold. I still have the plans. I may try that in the future.

 

I wouldn't have believed it if I didn't watch that video, and it seems genuine, but I wonder how much the power is restricted, especially under a heavy load? I don't get why you'd try to set up something like that, or a multi setup, when you could just get a small ~350-400 cfm 4 barrel, or even a progressive 2 barrel, and have better acceleration, top end and overall power, still with excellent MPGs if you drove responsibly.

 

You know, propane will get you better mileage, runs very efficiently, go longer between oil changes, and will clean your engine. Plus, propane is cheaper than gasoline. But, you loose about 10% horsepower compared with running gas. Only real problem is finding a filling station that will fill your tank.

 

he linked the thunderhead289 video with the maverick in the start of the thread. Speaking of, this thread is really dumb. Just a bunch of base level theorycrafting

 

It's also called bench-racing, since forever, and is pretty much the backbone of the automotive hobby for the majority of the people involved in it. Only a small percentage of car enthusiasts actually spin wrenches, most of the time it's just people BS'ing about things they'd like to have, or how they'd modify something. Before everything was searchable on the net, it's how ideas, good and bad, were hashed out.