maximum milage project

[big10ratrod77]

well i would like more horse power to

[glock35ipsc]

I think you are expecting too much from a 200,000 mile engine. Tune it to run it's best, and when it finally bites the big one, rebuild it or swap in a 5.3L/4L60E for power and mileage.

[big10ratrod77]

dad says when it dies i can build the 350 which sounds to be fun but a 350 tough i might never get to build it if i take care of it

[71swb4x4]

Originally Posted by big10ratrod77

well i would like more horse power to

Why didn't you say this in the beginning? You want to add all these "go fast" goodies under the guise that they will increase your fuel economy, when the REAL reason is that you will go faster. If you would have said go faster in the beginning you would have much different answers.

The best compromise would be to add a 700r4 and then build the motor. You will have decent gas mileage and decent power.

[3r!c84]

hold it to the floor untill she go's
then build that 350 like u wanted

[68 TT]

Anything you do to increase the air flow into or out of the engine will ultimately decrease your fuel economy if you are running the proper air to fuel ratio. More air in = more fuel in to compensate so 1.6 rockers, headers, dual exhaust & open element air cleaners are a waste of money if you only want fuel economy. They are great for power but not for gas mileage.

Things that will work:

Use a factory clutch fan with a clutch that works. Toss the stock rigid fan and never use a flex fan, they both waste HP. Electric fans are just a trade off of extra drag from the extra alternator load vs the loss of parasitic load from the removal of the fan and add a whole lot of complexity that is not needed. I just got a perfect seven blade clutch fan for $12 at the wrecking yard.

Taller gearing to a point helps but too much of a drop will make acceleration and city mileage plummet. With 2.56 gears my Malibu got worse mileage than it does with 3.42's but with 3.73's it gets worse mileage than either. 2.73's were better than the 2.56's but not better than the 3.42's. You may have to experiment to find what gearing works the best for your truck. The local wrecking yard sells gear sets on the carrier for $47 so gear changes are cheap. I was even able to return a set that didn't work well for me.

Use narrow tires with smallest diameter possible that doesn't look funny. This will keep the rotating weight and rolling resistance to a minimum.

Bigger diameter rims are heavier than smaller rims and increase the rotating mass you are pushing around. Stick with 15's if they will clear your brakes.

Aluminum wheels are generally lighter than steel but some are pretty heavy so weigh what you have and compare them to make sure it is going to lighten the weight with whatever you choose.

Anything you can do to reduce rotating weight is a gain of gas mileage and will increase rear wheel horsepower. An aluminum driveshaft is worth five horsepower to the rear wheels and will improve your gas mileage. I got an extra mile per gallon out of the driveshaft swap alone on my Firebird.

Tune the carburetor for maximum vacuum and give it the most timing advance you can without hard starting or knock. This will make what you have to work with the most fuel efficient possible.

If you can put in an overdrive transmission do it. The lower you can get the cruise RPM's the better unless it lugs down the engine so it is below the power band. With an automatic it will just downshift but with a manual you can use more fuel trying to push the engine at too low of an RPM with too high of a load. Shoot for 1700 to 2000 rpm at your cruise speed.

A manual transmission will consume less horsepower than an automatic as a general rule so it will put more power to the wheels and get better gas mileage. An SM465 weighs 100 pounds more than a T-5 so in addition to the overdrive gear you gain with the T-5 it will also drop about 100 pounds of rotating mass off the drive train to make it even more efficient.

If you can run a T-5 transmission have the overdrive gear swapped out for a steeper OD ratio. I was able to get a 38% overdrive 5th gear for my T-5 and it made the 3.73 gears much more fuel efficient. I believe the transmission shop told me the gear came out of an S-10 application so you may be able to find a T-5 with the 38% OD all ready in place. All T-5's are basically the same strength wise so any GM donor vehicle with one will work.

Reduce vehicle weight. Anything you can do to reduce vehicle weight will increase fuel economy and make it more powerful too. Lose that 100 pound step bumper and put on a 30 pound sport bumper. Put in a set of lighter late model bucket seats. That old bench seat is a lot heavier than you think it is. The stock low back bucket seats in my Camaro are 30 pounds heavier than the late 80's high back bucket seats I got out of an S-10 Blazer.

Make it more aerodynamic. Replace those towing mirrors with smaller sport mirrors. Lower it as much as you can. This will reduce the frontal area exposed to the air by hiding more of the tire from the wind. There is a good reason people who run top speed events like the silver states rally slam their cars and shave the mirrors. Any reduction in frontal area is free MPH and efficiency.

[clinebarger]

I know some of this has been covered but its worth reading




FACTORS THAT AFFECT FUEL ECONOMY:

Axle Ratio

Numerically lower axle ratios generally produce better highway fuel economy. The exception to this is if the engine is "working" exceptionally hard, (heavy vehicle loads pulling a trailer, small engine in a large vehicle ... ). In these cases a numerically higher axle may provide better fuel economy. Numerically higher axle ratios will also tend to provide more fuel economy in congested city traffic and stop and go conditions.

Brakes

Brake drag (even a minimal amount undetectable by coasting), can have a significant negative impact on fuel economy. Pull upward on the brake pedal to assure that the stoplight switch and cruise switch at the brake pedal are full and properly adjusted. A "click" sound when the pedal is pulled upward indicates that the switch was improperly adjusted. This causes the front brake pads to lightly rub the rotors, causing a fuel economy loss, without generating excessive heat or brake pad wear.

Driving Habits

Frequent short trips (less than 5 miles), especially in cooler ambient temperatures (less than 65 degrees), will necessitate fuel enrichment on start-ups, especially after "soaks" with the engine off for approximately a half hour or more.

Frequent accelerator pedal movement while driving will reduce fuel economy because of fuel enrichment during the periods of acceleration. Under such driving conditions the torque converter clutch (TCC) also disengages, contributing to fuel economy losses. Prolonged idle periods reduce fuel economy especially in cold ambients when vehicle is allowed to "Warm up".

Fuels

Oxygenated fuels, with methanol and/or ethanol blended into the gasoline have lower energy and thus reduce fuel economy. Typically there is about a 1 MPG penalty for a vehicle which gets 25 to 30 MPG on 100 percent gasoline.

Using fuels of a lower octane than the vehicle was calibrated to will cause increased "KS" Knock Sensor system activity. This will result in a net decrease in spark advance and thus poorer fuel economy. Using fuel of a higher octane than the vehicle was calibrated for WILL NOT increase fuel economy.

Variations in how much fuel is added to the fuel tank during re-fueling can greatly affect calculated fuel economy. These effects decrease as the distance traveled and the number of tank fillups increase.

Green Engine

New vehicles have not yet had an opportunity for the engine to break in, (rings to seat ... ). A typical engine will take 3 to 5 thousand miles to break in and during this time period a gradual increase in fuel economy can be expected.

Parasitic Loads

Air conditioning and/or electrical loads, (headlights, heated backglass ... ) also result in lower fuel economy, (typically less than 1 MPG difference, each 10 AMPs takes approximately .4 MPG).

Road Conditions

Road surface condition impacts fuel economy. Gravel and/or pot holed roads decrease fuel economy. Hills (vs. level terrain) also negatively impact fuel economy. Even gradual unperceptible increases in elevation result in real measurable decreases in fuel economy. Similarly, driving in the rain or snow decreases fuel economy.

Suspension

Vehicle suspension misalignment can cause poor fuel economy. Check all four tires for abnormal and/or premature tire wear.

New tires, tire rotation, and/or front end alignment may be required to correct fuel economy.

Tires

Performance tires and/or tires with larger "contact areas," (like 60 series aspect ratio), can cause as much as 3 MPG lower fuel economy when compared to hard "thin" tires. Find out if the tire size currently on the car is the same as original equipment. Replacement tires tailor than original equipment tires cause the odometer to read LESS THAN actual distance traveled. This will result in lower calculated fuel economy than actual fuel economy.

Tire Pressure

Harder tires, (more air pressure, or different tire compositions) result in better fuel economy. Do not exceed maximum pressure as labeled on the tire, typically 30-35 psi. The disadvantage of this is that the greater the tire pressure, the harsher the vehicle ride.

Transmission

On 4-Speed automatics, it is possible to drive the vehicle in 3rd gear rather than "overdrive" and not perceive it. Typically this condition occurs when the shift indicator, or the shift linkage/detent is misadjusted. Misadjusted shift linkage can also result in improper signals to the ECM, which can result in less spark advance, and results in a drop in fuel economy.

Driving a vehicle in 3rd gear rather than overdrive at highway speeds typically results in a 3 to 5 MPG penalty.

Torque Converter Clutch operation is essential for good fuel economy. A non-locking torque converter typically results in a 1 to 2 MPG penalty at highway speeds.

Vehicle Weight

Each 125 lbs. of additional weight results in a .3 MPG loss of fuel economy. Thus, additional passengers, luggage ... will decrease fuel economy.

Vehicle Wind Resistance

More wind "DRAG" means less fuel economy. Thus, hang-on luggage carders, cat toppers, open windows and/or open trunk... mean less fuel economy. (See "Driving Habits").

[big10ratrod77]

the last to yall wrote so much my brain twiched ill have ot let it soak in
i could drop the reese hitch, and yes i like power i want somthin like the new corvette that gets 30 sum mpg and a good bit of power in truck form. when it comes to my driving habits 95% of the time im realy light footed.

[3r!c84]

if u want power,speed and good MPG.a truck is not right for you.

[glock35ipsc]

Gen III Vortec engine, automatic overdrive trans, and the right gearing will get you low 20's.

[68 TT]

Originally Posted by glock35ipsc

Gen III Vortec engine, automatic overdrive trans, and the right gearing will get you low 20's.

I got 18 mpg out of my 02 Tahoe with 1000 pounds of stuff in the back doing 75 mph on a 900 mile trip through the mountains and back. On flat ground and lightly loaded it will do 20 no problem.

[clinebarger]

Originally Posted by glock35ipsc

gen iii vortec engine, automatic overdrive trans, and the right gearing will get you low 20's.

x2!!!!