Thanks for putting some pictures up. You could go to town with weight reduction & aero mods with that thing!

- Grille block the size of a windshield
- Removal (or downsizing) the gargantuan side mirrors
- Removal of the stepside will reduce drag and weight
- Removal of those weird prongs on the front bumper (less weight)
- Tinting the windows will drastically reduce the need for air conditioning
- Maybe lower the vehicle several inches

occupant -

Maybe these are still for sale :
MILEAGE MONITOR (vacuum gauge)
https://ideamaster.com/mm.htm

I originally saw it in this post by George Wilson :
Just bought and installed a vacuum gauge!
https://www.gassavers.org/showpost.ph...2&postcount=10

CarloSW2

If you want a vacuum gauge, just get something standard fair off ebay and hook it up. Other than that, *shrug* Carbs suck precisely because of their lack of precision, :)

Not sure how Warn does it for the full size, but the Warn hubs for jeeps are good for a rebuild once a year. Some new bearings and seals might do you good.

Not sure about the exact gen of your 700R4 but you might have a vaccum powered lock up coverter.

Does it use u-joints or CV joints? Some slop might be costing you some efficiency points

lol, i like the swiss cheese Idea. It has 2 barrel deactivation haha. You drive it easy, it uses 2 of the 4 barrels, hit the gas the other 2 open.

Speaking of carbeurators, ever consider getting a smaller one? I would imagine a stock one would flow quite a bit less air and fuel. If you don't want to go to such drastic measures, you might consider SeaFoam before your next oil change. It is just about the most amazing product for old gummed up carbeurators and motors ever created. Not to mention the cloud it produces is second to none :D

I do feel your pain though, my car started off getting a solid 9-11 mpg, YICK.

I second this man. I'll list a few key points to this great option.

1. Old limo's have a very small market, most people who want a limo are going to be getting a new to slightly used one, not some ghetto a$$ hooptie' haha. Most Limo service companies also have to update their models to stay attractive and competitive.

2. 99.9% of the time they are taken care of exquisetly from the time they are purchased till they are sold. This is mostly due to the fact a new limo is a rather large investment, and they have to be able to get their occupants from A-B with no reliability problems. Maintanence is the best way to keep it like new.

3. They're usually driven very nicely with mostly highway miles. I guarantee you've never seen a limo power sliding around town haha, mostly because the occupants would NOT like this at all.

4. Most importantly, If you get an older town car, I wouldn't be the only one with one on this site :-)

5. The misc. cool factor, what kid doesnt' want to get chauferred to school in a limo? Most limo's are the top of the line luxury models when new as well, so you get a real nice ride with the sweet options. Entry/Exit is easier than climbing over seats and such (never figured out why suv's and van's don't adopt 6 doors like some Limo's. Big trunks to throw your stuff in. Climate control systems designed for maximum comfort of ALL occupants, where as the SUV is mostly desinged for the first 2 or 4, the ones in back are usually cold (atleast in EVERY suv/van i've ever ridden in)

Ebay is full of Old Limo's noone wants, I'd imagine there are even more if you really look for them.

Ok, got one more consideration.

I used to have a 81 Plymouth Reliant, with a Mitsubishi 2.4L in it. On that car I leaned the idle mixture down to a point where the engine was not running smoothly, at all and would buck and snort, at a stop light. However, my mileage went from 22-23 mpg to 27 mpg.

I don't think this did any wonders for it's smog compliance, so this is a user beware. I readjusted the idle mixture before I had it smogged, and it passed fine. I couldn't see that it caused any other mechanical issues, for the motor, carburater or so forth. What it did apparently do, was to keep fuel from being dumped down the drain, keeping the idle path working full time, when the engine was just driving us down the road.

I don't know if their is any way to do anything on that carburater, but I believe my 87 carburater has a vacume bypass, that allows the idle circuit to not pull any fuel when the engine is above a certain rpm. The other thing which could be done, but I don't know if anyone does, is make a vacume bypass circuit for the regular jet's, so that the circuit can have a release that allows the fuel to be cut off, entirely, when your coasting, in gear.

Anyway, don't know if any of these are something you can or want to do, just thought I'd throw them out their, in case.

*Edited*

when I drove my 66 suburban home from san diego to phoenix, I got 19 mpg cruising at around 75 mph. It does not have an overdrive or lock up converter and was revving at over 3000 rpms because of the 3.73 gears. I believe this must be close to where peak torque was so the engine was very efficient. My 68 firebird also pulls similar mpg numbers. I havent even started trying for efficiency in those, they are just tuned up.

I found your post in the garage so questions I had previously posted did not need to be answered as they were answered there. So far I know its a 4 wheel drive 84 sub with a 700 R4, 4 barrel carb and a clutch fan.

One of the problems is that its a 4 wheel drive. Do you need 4 wheel drive? You could lose a lot of weight and gain mileage if you converted to 2 wheel drive but that may not be an option. 4WD causes a sure drop in mileage but even still I think there is potential for a LOT better mileage. If you are driving mostly around town then there might not be much to be gained in mileage because thats a lot of weight to get up to speed repeatedly. but highway mileage can be improved significantly
Here are some questions I still have

What is the gear ratio in the rear end?
What carburetor is on it?
What intake manifold and exhaust manifold/header?
What is the exhaust configuration?(single, dual, dual with crossover etc)
What do the spark plugs look like?

^^ true buuut, I wouldnt completely discount a couple things. There is the added weight that must be dragged along, accelerated everytime you stop, then there is the rotational mass, the transfer case, driveshafts, front gears they are maybe more of a penalty because that weight has to be spun rather than just pushed along. This drags a lot on the engine, It may not make much difference on a flat open highway at constant speed, but as soon as there are hills or changing speeds it starts making a difference.

If you have a quadrajet carburetor, you can get decent mileage if they are tuned correctly, but they are more difficult to tune than other carburetors. I personally prefer the old carter, or current edelbrock carburetors(same thing). They are easy to tune and its easy to change idle, cruising, or WOT(wide open throttle) fueling characteristics. My firebird is lean to the point where under constant cruising it surges just slightly. I should point out that too lean a mixture will cause problems passing emissions just as too rich will so be careful to keep it in the middle.
Opening the exhaust will help, an X type crossover aides in scavenging and helps evacuate the cylinders of spent gasses, a smaller set of headers should help with low end torque and exhaust flow over the Log style manifolds if thats what you have. If you have the cast iron manifold, I doubt you will see too much difference in anything with an aftermarket aluminum one, but there is weight to be saved there if you can pick one up cheap.
Some attention to front aerodynamics would help a bunch Im sure as there is a lot of frontal area and obstructions under the truck. Then if you want to continue that, a full belly pan should make a huge difference on a vehicle that high, with an undercarriage that messy and huge.
I dont know how your gearing is but I believe you want to gear it such that your engine is reving at peak torque rpms where you will cruise most.
I dont know if you are against lowering a 4WD vehicle, seems a little wrong, but if you arent a lot can be seen here in terms of drag reduction.
smaller mirrors, losing the running boards, blocking part of the grill, an air dam, removal of the side handles on the b and c pillars, and possibly a rear cusp spoiler will all help with drag reduction too. After all these things you will for sure be getting 15 mpg, maybe more.
Heres a pic of my burban in case you care. It gets 14-19 mpg with a 302 ci small block chevy, th350 automatic transmission and 3.73 rear gears. It has 2002 chevy Z71 17" aluminum 6 lug wheels on it. This is before I started the restoration, it will be near perfect when Im done.
https://memimage.cardomain.net/member...589_4_full.jpg

He has Warn hubs which lock out everything from the stub shafts on in

To do a 2WD conversion he'll either need a new tranny, or a new tail housing along with a longer rear drive shaft. For true 2WD he would have to replace the front axle with one from a 2WD truck. Could be more $$ and work then gain. Replacing his wheel bearings with modern lower friction versions would probably be a better bang for the buck.

For Jeeps atleast. The wheel bearings used in YJs and XJs were crap, swapping over to the TJ style would net a small improvement.

True, but he would still be lugging around a now useless transfer case and front diff.......