hi all, glad to be here I've been a mechanic for 25 years mostly back yard but picked up a lot of different techniques by reading and doing i love cars, whether its sport compact or classic muscle,working on them and playing with different ways to make them go fast, lol, the technology out there is awesome for anyone to get their hands dirty and learn how to work on your modified car. well i'll be coming in the forum time to time to help or even answer questions if you want or even to learn from other people as i don't know everything! I may know a lot but i can still learn from others and people have different experiences, which is good. Actually i my next project is to take a 87 Gmc truck and put it into the 35-40 mpg range with a 350 consistently any body have any tips or advice i will welcome it
Thanks
BTW i'll keep you updated

yea, dont use tbi...if you put a diesel in it then your gas mileage is awsome becuase you no longer need gasoline(ha lame joke)..... wouldnt you have to change cam, heads, intake,exhaust, 8 port injectors with, stand alone programmable computer to modify spark and air fuel ratio curves, thats alot of work to get what you need? any one chime in on this im curious too./

Welcome to the forums dfunk.

While I am not going to say it is impossible the fuel economy goal for the truck is not realistic.  Nothing is impossible if you have enough time, money and patience.

First up some links from the EPA fuel economy guide:

This most likely is similar to your vehicle.

http://www.fueleconomy.gov/feg/findacar.htm

Here is link of a 2010 GMC it is not an apple to apple comparison.  However, it gives an idea of the amount of the increase in fuel economy in trucks over the years.

http://www.fueleconomy.gov/feg/findacar.htm

I am no engineer by any means so that is my disclaimer .  There are several concerns to contend with. 

First what is the primary purpose of the vehicle? Is it a truck used for hauling? If so that my be very problematic to increasing fuel economy.

Rolling resistance is something that will need to be optimized.  If the truck is a traditional 4X4 it take substantial amount of power to turn the gear train.  Almost always a 2wd will have better MPG than a 4wd.

Weight is another concern.  Trucks are built sturdy (most of em) and there fore weigh considerably more than traditional cares.

Aerodynamics are another concern.  If I recall correctly the 87 GMC is very boxy.  The harder it is to push it through the air the more fuel is consumed.

Fuel distribution and control could be a good place to start.  Many of the improvements in modern vehicles are derived from this.  If your truck is a TBI upgrading to a multiple port injection would be a good start.  Edelbrock use to have a TBI ot MPI conversion.  I do not know if they still do.  Peruse through this link for what is current.

http://www.edelbrock.com/automotive_new/mc/efi/pf_intro.shtml

There is also a huge offering of stuff directly from GM:

http://www.gmperformanceparts.com/Parts/showcase.jsp

This would just  be a start.  I would ask you the same question I often ask customers wanting to fix noise and other unusual things.

What is the dollar to aggravation ratio?  In you case what is the MPG improvement to dollar ratio?

Good luck with it what ever course you decide to pursue we might be able to help out some.

Sam