I have a 1971 D100 just a plain old automatic farm truck with no upgrades. I have recently started looking into the holley 2d fuel injection systems. Does anyone know what the fuel mileage gain would be with this 2 barrel fuel injection system? Also Are there any other ways to get better fuel mileage. I am looking for cheap ways although I do have money to spend.

please let me know

Zach

 

A gear change would get a mileage gain. Do you know what ratio the truck has?

 

The one I have now Has 355 gearing with a 4 speed hemi overdrive transmission. So I think that's good with the tires I have.

 

Agree. I have no experience with the holley system. A well tuned carb engine with no emissions should get decent fuel mileage.

 

Ok it's an auto ? You might get 2 mpg better, maybe ! For the expense you can buy a lot of gas !!! A change to a 3.23 gear set in the rear would do more for mileage. A D100 I would guess has a 8 3/4 differential, easy to change..

 

Let's start with what you are getting NOW?

How heavy is your foot, realistically?

What sort of roads do you drive?

Do you actually drive a LOT on the highway, or mostly secondary roads?

In other words, for the condition of the vehicle, the roads and the way you drive, you might already "be there."

YOU WILL NEVER pay for converting to fuel injection, if you drive that truck another 20 years.

 

Well when I am out messing around I will get on it but when I am driving it I can keep a light foot. Seems like the fuel injection would pay it self back almost within a year.

 

Oh and the first question, I never figured for myself but the one with the 4 speed and 355 gearing My dad claims 13. That is with a 650 carb as well. It also has 360 heads. I think the 360 heads help the fuel mileage because it lowers the compression and flows more.

 

I don't want to rain all over your parade but the 360 heads could be decreasing your fuel mileage. The key to these smaller engines with stock or close to stock cams is port velocity. This is what will increase low end power and increase fuel mileage. If you were to put on a set of late 80's 302 swirl port heads, even with smaller ports than the 360's, you'd see a significant improvement.

I tried the 360 on 318 years ago and it was a mutt until it got spinning above 3000 rpm.

 

My '89 gets around 14-15 when I drive it the way I should. 10-11 when I drive it like a stolen hemi cuda. Alot of the TBI guys are always swapping for carbs. If you got a donor vehicle or someone that wanted to do a full swap, that might be the cheapest way to get EFI. If you're keeping the 318 stock or close to it, might be an option worth looking into. My $.02. My TBI seems to run a little on the rich side, so I've actually been considering swapping to a Carter 2 barrel setup off of a '71 Satellite (because it's free).