MPG

[that-son]

"I start my 710 and it goes to slightly fast idle and I back out and drive one block to a stop sign. Pulls away perfectly and drives for 4 or 5 blocks to a stop at the highway. Drives smooth and pulls evenly and firm in all gears." - datzenmike

 

tried driving off today before the truck was completely warmed up and... yeehaw!  it was like riding a mechanical bull.  when cold she idles at 1200rpm for about 3 minutes then goes up to 2000rpm until i step on the accelerator.  when she's warm, after sitting for about 30 minutes or longer she idles roughly between 5-600 rpm then goes up to 800 again when completely warmed up. 

[datzenmike]

If well adjusted it should run as mine was described. It slightly lacks power but runs smooth without hesitation. Try spraying the linkages with WD-40 and work them to make sure they are not sticking. The choke may be adjusted for richer or leaner by loosening the three screws and twisting the round black choke heater. Richer when colder. Once you get it, it should automatically be right for any temperature.

[arizonajones]

I get 28 in town and 32 MPG at 65 with my L20B. I was getting about 5 MPG LOWER for each before I swapped out my distributor for one that wasn't worn out. That sucker has already paid for itself since that was more than 1 year ago.

are you running a hitachi or weber? mechanical fuel pump? what brand distributor? I want to copy whatever setup gets you that kind of mileage

[datzenmike]

Part 32702-E9816 about $25 at the dealer will get you over 30MPG.

 

 

 

It's 16 tooth pinion gear assy that will increase you mileage indicated by about 20% . :lol: :lol:

[arizonajones]

Mike I see your LOL faces... this must be the wrong ratio.  <_<   I guess I could just pretend like my mileage is awesome but my commute just got longer...  :lol:

[Charlie69]

Jetting a Weber is just trial and error.  I found out a long time ago that there is a lot to properly tuning a Weber DG carb.  There all all kinds of parts that can change the way they perform.  Best advice I can give is get intimate with your Weber and it will pay off in the long run.  Get a jetting kit and experiment.  Altitude has a large affect on the performance of these carbs.  Keep your air cleaner clean and I always run electronic ignition on my L motors.   What works for me in Phoenix will probably not work for you where you are.  Also buy quality tuneup parts!  The old saying "you are what you eat." applies to your vehicles also.  I also buy premium gasoline.

[Buzzbomb]

 

Did you leave it stock or did you change the curve?\

 

No, it's the stock curve. When I had a busted advance mechanism in my OEM distributor, it looked to me to be kind of a weird setup to mess with regarding a recurve. I've done it on my Chevy because the parts are readily available, but on my truck, I was too leery about it. Maybe it's just as easy, I don't know? not sure where I'd get the springs and such. I also have to pass a yearly emissions test, so it's best to keep it as close to stock as possible, at least for me.

 

 

are you running a hitachi or weber? mechanical fuel pump? what brand distributor? I want to copy whatever setup gets you that kind of mileage

 

I'm running a stock Hitachi with a replacement mechanical fuel pump and all the stock emissions stuff. The replacement distributor was a Cardone unit, and it came complete with the matchbox. It was a SUPER deal at Advance Auto Parts for around $100 for the whole shebang shipped right to my door. I will say that I have a 5 speed transmission in my truck, and as we all know, that can make a big difference, especially on highway driving. I also have a muscle car style turbo style muffler with 2 inch inlets and outlets. When I put that on, that made a big difference. Too bad that muffler rotted out and I have to replace it, but it'll be with a new turbo style muffler.

[Charlie69]

I am running a Weber DGEV purchased from Pierce Manifold on my 86 King Cab.  I have played with jets emulsion tubes venturies and Manny other parts.  Like I said earlier elevation plays a big part on how they perform..  I have a Z24 in my 86 you have an L20B in your 1980 so what works for me will not work for you.

 

I had 2 Identical trucks a few years back and Weber's on both.  They had the Z20 in them they were 84 720's with the 5 speed.  I could get one putting out 28 miles per gallon and the other the best I could get was 22 miles per gallon.  The Weber's  had the same parts in them.  Each vehicle is different so again what runs great in one does not men it will do the same in another.

 

Until you know and understand what you are working with you will not get these results.  Copying a setup does not equal success.

[MaddieCycle]

I have an '86 4x4 KC 5 speed that runs like a top, starts very easily, no smoke, burns usual amount of oil, and has good compression.  Pulls 85 on the freeway with no complaints.  No matter what I do or how I drive, I am stuck at 15mpg.  I live in CA so I have all kinds of smog stuff and can't mess with anything out of fear of failing my next smog inspection. I've resigned myself to just dealing with this poor mileage but dang it is not good!

[datzenmike]

Probably close to right. 18 sounds better.

 

Air up the tires to the high side recommended. Harder tires are easier to roll.

Stock width tires are better than wider ones.

EGR does not affect mileage only reduces power slightly at part throttle

Non California ignition advance is 5 degrees rather than 3. You can always reset it before testing

Empty everything out of the truck. Even a coffee mug has to be accelerated up to speed.

 

Driving habits are changeable.

Practice driving without touching the brakes like it's a game. Just remember the every time you brake you are throwing away the gas you used to get you up to that speed, including the coffee mug. Look ahead and anticipate stops and slow downs. Preserve your motion as much as possible. If the next light up ahead turns yellow let off the gas and roll towards it. Leave more space between you and the guy ahead, if someone cuts in, space your self again. Keeping up with traffic like it's a race is very expensive of gas. Leave 15 min earlier and take your time, avoid thinking you are in a rush. Drive like there is an egg under the gas pedal, squeeze it, accelerate smoothly. Use the slower lanes to avoid delaying the faster cars. Avoid warming up your engine. It does not need it and it will warm up way faster if you drive it. If cold, install a block heater in the winter. Avoid short trips when the choke will be on more than off. Keep a log of mileage and gas used between fill ups and a small calculator. This is like having a weight scale when dieting and will keep it fresh in your mind what you are trying to do. Motivation.

 

Anyone can get 10% better mileage