So no biggie but wondering what else I could do to squeeze more mpg out of my rig. It's a 76 302 in a '84 Bronco.
Upgrades already done:
Edlbrock proformer intake
Edelbrock 500cfm carb
MSD spark box
3.73 gears (from 3.08)
New front end (wheel bearings, tie rods, ball joints, alignment)

Running out of things to try other then thinner tires (31x10.5 now). Was thinking of one of those fuel injection conversion kits.

Like I said it's not a big deal just trying to get most bang for gallon.

 

If you’re doing all of that just to improve mileage, my guess is you’re spending way more money on the changes than you would save on mileage efficiency.

You’ve probably already covered the basic options. Best way to improve mileage is throttle management - light foot, coasting.


What is your current mileage?

Is this a daily driver/work truck/pleasure truck?

 

Two main factors you'd want to study and focus on with the engine tuning side of things are Ignition, in terms of a ensuring a good HOT spark and especially, the Ignition timing curve.

A defective (or misadjusted) vacuum advance alone will reduce highway mileage 3 to 4 mpg. The mechanical advance from the factory is also very conservative and "lazy". There's probably another 3 to 4 mpg hidden inside the distributor. New replacement ignition parts alone does not necessarily mean the ignition system is working correctly. Ask me how I know. One piece of gear that really helps with engine diagnostics and tuning is the oscilloscope. The OEM ignition systems are generally very, very good when everything is working correctly. But, a lot of the aftermarket replacement parts are crap. An ignition scope lets you see a visual representation of the ignition system in real time. If there is a defect anywhere in the primary or secondary wiring, cap, plugs, coil, whatever it will show it instantly.

The second factor is carburetor calibration or tuning particularly jetting and power circuit tuning. One thing to keep in mind depending on the particular year in question is that engine tuning in terms of power and efficiency really took a back seat to emission reductions for a while. They basically crippled the motors from the factory by reducing cylinder compression, + some camshaft timing jiggery-pokery (and a lot of other things) that wasted lots and lots of fuel.

 

Irridum plugs with Ford Racing wires. Also a MSD coil too. My current mpg is 7-8 in city & 10ish highway. Shes one of my dailys.

 

Tedster9:
Any vacuum advance/counterweight options that are better then the stock options? It's set at about 12°BTDC.
The block is a 76 with stock heads. No emissions stuff on block or truck. It does have a aftermarket cam in it. Not sure what the specs are on it. The previous owner of engine put it in It's a step above stock though not like a "***** Thumpa" or anything... As much as I want one...

 

Mainly it's a matter of mapping out the timing curve at different RPM. Initial timing is just a small part of it. '76 was right in there in terms of some strange stuff going on, the air quality regulations were imposed but the engineering hadn't quite yet caught up with it. So they had to do some things that work at cross purposes in terms of engine power and efficiency. Nitrogen oxides make smog, and this pollutant is elevated when an engine is tuned for best efficiency, basically. So combustion chamber design, and camshaft or valve timing, compression, there could be some roadblocks built in there. A basic bare bones V8 can achieve 25 hwy mpg in a car with some tuning.

David Vizard wrote the book on carb tuning. Quite a lot of it is excerpted online, might pick up a copy of that. What I found in tuning is a whole bunch of gasoline can be wasted straight out the tailpipe with little noticeable difference in performance. In fact it will likely be worse. But it quickly becomes a matter of how much is your time worth - and money, and diminishing returns. EFI kit sounds promising, but is that worth it, they aren't plug and play either.

 

Times 2 here. Not much you can do to a 302 in a full size Bronco to improve mileage. Ain't got the torque to move it easily. You could put a 351W in it and the mileage won't change one bit, but it will get up and go a lot quicker.

 

Alrighty. Just thought I'd ask. Thought I might have been overlooking something but probably just overthinking it. Thanks for the Input guys.

 

I bet the carb could use some tuning. Get yourself a wideband O2 sensor and gauge and then try to dial in the mixture closer to 14.7:1. That is the main difference between a carb and one of those throttlebody EFI systems, EFI is designed to target the ideal air-fuel mixture.

 

Post a clear, sharp close up picture of a couple spark plugs.

You can do way better than 10 mpg hwy. Most people don't necessarily want to get that far into tuning. Not pointing any fingers at you, to be sure.

It's just that too many people think a couple adjustments to the mixture screws and maybe some magnets around the fuel line, maybe some propellers for the intake, all that will double the fuel economy. There are no "secrets" really, just careful close setup, and tuning, to factory specifications. Ignition timing curve, and jetting, basically. Highway cruise is where the improvements are to be had for the most part.

Carburetors are designed to provide an almost identical fuel map as EFI, they just get there a different way. Carbs are typically so mis-tuned and off the beam that economy drops off a cliff. That's one reason they went bye-bye, it isn't so much that they don't work very well, but the fact is not everybody can or wants to be a mechanic, or can afford to hire one.

 

When you changed gears, did you get the correct speedo gear for it?
What is your other daily driver and mpg?

 

Agree! and the EFI systems suffer from the same drawbacks as a carb when atmospheric temps exceed 80+ F degrees of your dealing with very cold weather (mpg wise)

 

Yes I did change the speedo gear. Surprisingly enough the dealership was still able to get those for a 30+ year old truck.
As fo rmy other daily. It's a Challenger.

 

So scence I have side pipes for exhaust I'd need an O2 for each side and a gauge something like this?:


this one?

Or this one?

 

A single wideband O2 sensor works fine installed on a single pipe of a dual exhaust. The exact location where it's installed is kind of important though.