What the deal with the gas mileage?

[1FaastC10]

Originally Posted by bumpsburb

The truck is equiped with the TBI, not sure of the size if it has one. Would it help if I put fuel injection on it?

hmmm, would it help if you put an engine under the hood too? TBI stands for Throttle Body Injection. you already have fuel injection.

I can assume the power and MPG will increase when I install the headers and 2 1/2 inch pipes on it.[/QUOTE]a wise man once told me, assumption is the mother of all fawk ups.

[piecesparts]

(NEVER ASSUME ANYTHING) You can assume a lot of things, but just adding headers will probably NOT give you a lot more mileage. It WILL give you more available power, due to the engine breathing better. The theory of efficient air in and efficient exhaust gases out is nothing but power building at it's best. The fact that the engine does not have to use as much gas pedal to get the RPMs up since you have changed the in take and exhaust will give you a little better mileage, hopefully it will be noticeable. I added a MSD 6AL setup to my 91 Silverado 350 to get every ounce of burn out of each cylinder full of gas mixture. I believe that I saw an improvement in my daily driving performance. It cost for the wires, box and connectors but I am happy. The TBI is not all that bad, put a helical cut spacer under it and get more mixing in your fuel charge. Think about the injectors spraying on those butterflies and that gives you (I am using a unit from Poweraid) The rear end gears can be decided two ways; (1) take the rear cover off and look at the numbers on the ring gear and you can get to a decision on that (count the teeth) or (2) jack up the truck rear end and turn the rear axle, turn the wheel and see how many times the input shaft turns to get the rear wheel to go around one time.
By the way the guy above with the 2.73 gears and a 700R4 is really hurting for power and acceleration. My son's truck had a 3.08 rear end with a 700R4 and the mileage stunk. We put in a 3.73 geared rear end and picked up 2 MPG when the motor started to work easier.

[bumpsburb]

I always thought TBI was a type of injection but is not a true injection like on the engines produced today. I can be incorrect and will be "skooled" on it if i am. What type of shop should I look for to assist me in setting up my gear/power ratio?

Bump

[piecesparts]

TBI is an injection,BUT it is not a direct injection into each cylinder's inlet airflow path. TPI is Tuned Port Injection and the injectors are down stream of the air inlet to the manifold, where TBI has the injectors at the air inlet. there is a loss of horsepower in TBI due to the air/fuel mix capabilities and the efficiency of the system. The TBI will tend to mix gas and air ineffiicently due to the sprays of the fuel is on top of the butterflies in the TBI unit, this causes the fuel to lazily dribble into the intake manifold, where the TPI will spray directly into the air mix as it flows into the cylinder. The TBI can be helped with some of today's aftermarket items such as a spacer plate with the spherical cuts in it. This allows the fuel/air to mix more efficiently to get a good mix to the cylinders. I put one on my 91 Chevy and picked up a good lower end torque over the original setup (best money I ever invested).

Look for a shop that works on trannies and rear ends for a living. They may not be the Masters at what you need, but they can make your wishes come true. I found sdme calculations on wheel/tire size and RPM combinations in different magazines and also Edelbrock catalog has these in the back of their pages. I used these formulas and then figured out where I wanted the motor to run at 70 MPH and then made the gear changes and speedo gear changes to get them where I wanted. You will have to decide what you want and then get the gurus to support you. Also, look for a dyno shop in your local area and see if they have any ideas.

[bumpsburb]

Thanks,

I will add a spacer this week. I looked at them but was skeptical of the MPG boost they were claiming. Have you ever used a chip for improving gas mileage? Saw one on evilbay and it said a 10% improvement was guaranteed. Is this to good to believe?

Bump