fuel economies war

[Skulptr]

so my last 720 was a 4x4 SC 5 spd and got about 18mpg, unleaded fuel.

 

my newish 4x4 KC 5spd gets about the same. the engine in this one was yanked from the SC.

 

i'm looking to boost my economy, but seem to be getting no where. i put a weber 32/36 on it, but i know damn good n well it is not tuned right what so ever. every now and then it just wont stay running without the throttle, other times it idles 1100 and bounces at random from 900 back up. and randomly, when i shut the truck off it will stop, then fire back up on its own for a second blowing air out the carb. i also replaced all the fuel lines at the tank, have replaced the fuel filter 4 times in the last month (yes they were all plugged up), cleaned the filter in the pump, and the screen in the carb.

 

i also have free running hubs, but i have been tempted to put my manual hubs on from the other truck that i snagged.

 

 

i know i need to replace my fan clutch, but i cant find one for the price i like. my fan currently runs full speed full time.

 

 

so things to boost mpgs, and what your gettin now. i would love to know where i can get her to.

[metalmonkey47]

I've gotten around 30 witth a Weber on an L20B.

 

Only time I ever did it. Dunno what changed, but I've been doing about 20-25. $12 lasts me a day or two.

 

 

My 210 got nearly 40 mpg on the A15 with the Weber, MSD ign (made a nice difference) and ported head.

 

 

 

 

 

 

 

 

 

For your issue, have you checked the timing? I can get a smooth idle around 550rpm with a weber. and electronic ignition. I run about 14 degrees at idle with 89 octane to prevent pinging at high RPM's.

 

Clean idle jets? Primary and secondary idle jets are on the side of the barrels. Very easy to access. New fuel filter? Plugs, rotor, cap, wires?

[datzenmike]

A GOOD stock carb would be best for mileage. There is a fuel shut off on decelleration on the 720 that the Weber does not have, it's smaller too.

 

Check tire inflation and alignment.

Timing advanced as far as the motor will take for the gas you are using

Clean air filter.

Synthetic oil in trans, trans case and differential.

Engine in good tune.

Empty the extra junk out of the back.

Anticipate stops by looking ahead, practice slowing down gradually and NOT having to use the brakes. Every time the brakes are used you throw away the gas used to get you up to that speed.

[Lockleaf]

Tune it first off. Get it dialed in as much as possible. There are a number of things that can and should be adjusted on a carb. Also, did you buy the carb used? There are a few things that are common wear/maintanence issues with Weber carbs if you bought it used.

[I'm BLUE]

Car= 1973 240z

 

Trans = 82 zx 5spd

Tires = p195/60/r14

diff = 3.54 r200

engine = f54 block ... l28 ... 130,00+ miles on it

Carb = 4bbl Holley, ,, standard power valve, standard accelerate pump cam

Camshafts = stock l28e

wheels = light weight mini lites

Other = 70-100 lbs of tools/spare parts in back

Curb weight =2,400bs ? Ish ... give or take

Driver = 180lbs

 

City = 16... easy driving

Highway = 22-25 .... really easy aware driving .. cruising in late zx 5th gear ...

:)

[metalmonkey47]

Sorry to threadjack, but what weight/capacity GL5 does the H190 use?

[DOnatello]

Sorry to threadjack, but what weight/capacity GL5 does the H190 use?

 

untill it comes out the fill hole while sittin gon level ground, you work at an autoparts store, shouldnt you know this sort of thing? :huh:

[Skulptr]

I have no idea how to tune the carb correctly, and haven't found a guide I can understand. I also dont have a clue how to screw with the timing.

 

the way the truck runs changes constantly over the course if the day, literally. I am almost positive my fuel cut solenoid is going out. Theres times I'll drive and the moment I let off the gas it drops straight to dead. Start it again drive for a few miles let off the gas and it's fine again.

 

I have new fuel filters, I'm having to change the prepump filter once a week right now cause of rust.

 

I have no air filter period, it and the top plate got smashed during the engine transplant.

 

cap is new, nothing else is. Going to replace the plu gs today. Does anyone have the firing order so I can make sure my wires go back properly.

[DanielC]

1 3 4 2

[Lockleaf]

Go to your local auto parts store. Make buddy buddy chat with a couple of the guys there. Ask intelligent questions about your truck problems and listen to the answers. Buy a couple small things each time you are there. Make a very distinct effort to remember their names, and they will make sure to remember yours. Guaranteed one of them knows at least decently how to tune a carb. If not, one of their close friends does. Get to know which guys drive what, and if a guy drives something older than 1985 or mentions a project older than that, you know you have a guy working on carbs. If he is not doing his own work, he has a guy. I have worked behind the counter at Oreilly autoparts for 5 years now. These are the customers who I know by name, whos projects I am familiar with, and for whom I am more than willing to go out of my way to help. Some of them have even become friends of mine. It's true, lots of the guys in every store are complete morons and just talk out their asses. It should not take you long to figure out which ones know whats up.

 

Or go find a shop who specializes in carbs. :)

 

Best of luck man.

 

And to answer your original question. On small tires, 4x4, I have seen a best consistent 24mpg with factory carb.

 

From my current truck, which is a stock rebuild with a weber carb (that is less than happy) and 31x10.5 tires, I am getting around 16 mpg

[Skulptr]

I knew I forgot something, I'm running 33x10.5s

[DanielC]

An engine can run lean, and get good economy at light part throttle conditions. As you want more power from the engine, the fuel to air requirements of the engine demand a richer mixture.

Most carburetors measure the demand for this richer mixture by using the manifold vacuum.

The carburetor has a "power circuit" or a power valve.

 

A four wheel drive vehicle puts an extra load on the engine. Putting over sized tires on the vehicle add a lot to this extra load. Additionally, making the vehicle higher, causes the air drag to go up at freeway speeds. It may be a minor thing, but if you have big lugs on your over sized tires, when you are going 60 MPH, the top of the tire is going 120 MPH. if it hangs out where air hits it, that could also be affecting your drag.

 

So, you have raised the height of the truck. More drag.

The tires are a larger diameter. More drag

The physical shape of the tires causes, even more drag.

The larger diameter of the tires make the engine turn slower. You have to open the throttle to get the truck to move. This means way less vacuum on the engine. The engine goes into the "More Power" run richer mode.

I think that is a good reason why you are not happy with the fuel economy of your truck.

 

I know it will look "dorky", but try putting some normal height highway tires on your truck. I bet the mileage will improve.

[Skulptr]

If I do that I might as well drive my honda. I want to see someone do the work I do with 28" tires.

[Guest kamakazi620]

If I do that I might as well drive my honda. I want to see someone do the work I do with 28" tires.

^^^^^^^Well than WHY don't YOU???? Seems to me you make a thread on how to get better MPGs???? Right?? We answer ??? and tell you What you NEED To DO,and then this^^^^^^^ WTF??? guess thats why you'll NEVER get better MPGs :rolleyes: :rolleyes:

[I'm BLUE]

Locked fan clutch is going to kill power on any engine :blink:

[ronnny]

Ok you have a kc4x4. If you are getting 18-20 you are doing good. Without axle swaps for better gearing to make up for the larger tires you are doing better than good. I have an 85 regular cab 4x4 that i get 17-19 running 28.5 tires and a 32/36 weber that runs rich and is idled high. I will rebuild the carb and will get 19-20 out of it around town. This is good for any 4x4 little truck. I know others that get this for highway mileage. Get a 2x4 for better mileage or try little things to make it better but it will not get much better. My 81 that had a 2.2 that was a 2x4kc got 28-29 around town. Same carb that is now on my 4x4. Put on some electric fans will make a difference. No air filter is better for mileage but a lot worse on the motor. What do you do with your truck that is so special? That might help someone make a suggestion. With a welded rearend i go places the open would not take me but it cost me in tires. A better msd ignition would get you another mpg if you are not using it to burn more gas. Even on the general page ask about better mpg but we need to know what you do with your ride. We can tell you about a 210 wagon with a L20 and a 4 speed that slides over ruts left by 33's with a running start. It does get on the better than 23 range but of course not a 4x4.

 

Ronny