[Firebirdjones]

Originally Posted by OSE_NERO

Right now I have an '81 C10 single cab, long bed, two-wheel drive model pickup. I'm wanting/needing better gas mileage. I have a 350/350 combo right now, and would like to keep it that way, but if I can't really get any better mpg out of it, I suppose I'll have to swap it with an EFI motor QQ lol

My question is, how can I increase the gas mileage more?

Currently, I'm fixing the previous owner's neglect and putting life back into this behemoth. When I got it, I was probably getting about 6-10 mpg city. I never got to really do the whole calculating thing because I was always stretching the last dollars of my paycheck when I actually HAD work. Now though, I feel like I'm getting better mpg. I've put on an Edlebrock performance intake manifold, a Street Avengers series Edlebrock 600 cfm carb, Edlebrock breather kit and air filter, and have replaced all of the exhaust line, pardon the manifolds (which are next when I get income again). I have a 3" exhaust true dual exhaust line with Thrush Welded mufflers on each line minus cats.

I'm going to be honest and say that I literally have no mechanical incline, besides changing tires, batteries, headlights, and oil. That's only because I worked at Walmart's TLE section for two years. I love cars, and have a lot of stats memorized about them, but you hand me a wrench and I'll stare at you dumbfounded. I won't try to claim that I know anything that I don't, especially with this being the case.

I've been told that a bigger pipe, pardon the massive ones unless it's diesel, will increase both power and fuel mileage. I was also told an X-pipe would help, but not until I had my exhaust already put on. Does it? If so, should I do it when I get the headers put on?

I was also planning on lowering my truck a little bit to get the "bruiser cruiser" look, and to increase fuel mileage. I've been told that a lower stance will help aerodynamically to decrease drag, increasing mileage.

Also, I was planning on putting aftermarket wheels onto my truck (no bigger than 20s, and most likely 18s). I know that these won't effect gas mileage, but I heard that if I changed the wheels I would have to mess with the gearing of the truck since it was built and tested with the 15s. Is this true?

However, I was also wanting more power as well on top of gas mileage, but as of now, those roles have reversed. I've been told that you have to sacrifice one to have the other, but I don't want to believe that. I just want a nice blend of each.

I also just read about modifying the carb to increase gas mileage. However most of those people have "vanished". The way one man described it was that it ran on gas vapors instead of actual raw fuel and that it was more potent that way. Which, to the untrained such as myself, sounds like power while also boosting mpg.

I also know that on TBI and EFI that if you put a cold-air intake on the vehicle, it will give you some power and also increase gas mileage. Is it possible on a carburetor motor? And if so, will it have the same effects?

Lastly, I know that diesels and small tuner engines use turbos to boost power and I've heard that it WILL increase gas mileage and that it WON'T. So which is it? Does anyone know?

If anyone or a few people can help give me some insight to these questions or even suggest other methods (besides converting to CNG as it costs too much for me at the time), I would be thrilled to read them and think them over.

Thanks a bunch.

To start with, I'd prefer a quadrajet over that Edelbrock. Edelbrocks require their own calibration kits for any tuning. Speaking of which, the only real way to dial in any carb is with a wideband, otherwise you are shooting in the dark. That coupled with a correctly curved distributor will yield some gains in MPG. I shoot for a leaner 15.0 AFR for very light throttle and idle conditions, while still maintaining a safe 12.8 AFR under heavy load. And I generally go for about 16 initial timing with 20 degrees of centrifical built in for a total of 36,,,should be a good starting point for most engines give or take a few degrees. Then dial in about 12-14 degrees of vacuum advance with an adjustable unit, and hook that to manifold vacuum.

Done this way will give you the best all around performance and fuel economy you could expect from any engine. From there it's all basic stuff. Free flowing exhaust with an X or H-pipe, long tube headers, a good dual plane intake will all help.

Then attack all the HP dragging rotational weight. Dual electric fans will free up some HP and mpg over a mechanical fan, aluminum driveshaft is easier to turn. Lightweight wheel and tire package is easier to turn, then pay attention to the size and the tread pattern as these can affect mpg as well. You could go as far as lightweight viscosity oils throughout. A good working fresh air intake system is free HP. Basically anything you can do to make life for the engine easier will generally return you with MPG gains. You can really get nit picky here, but it all adds up. There is much more to do as well.

I get a respectable 14 mpg out of my 79 1 ton with a 502/400 turbo and 3.73 gears in a truck that weighs 5500 lbs. with some of these tricks mentioned. It cruises nicely at 65 mph at 26-2700 rpms. That's through a power robbing 400 turbo and that huge 14 bolt full floater.
I am doing a custom aluminum radiator with dual electric fans, a gear vendor overdrive unit to drop cruise rpm 3-400, and will eventually go to a lighter wheel/tire package. Currently the 16.5's weigh 65 lbs. each with E load range tires on it I should gain an easy 2-4 mpg with all these changes and put the truck nearly at what some of the new trucks get for mileage. Respectable for a 500 cube gas engine with a carb

My 72 4x4 blazer with a 6.0/4L60 swap gets 22 mpg with 3.73 gears and 33" tires, it weighs 4600 lbs. I run a lightweight wheel, and kept the tire width to 10.5", and a mild tread pattern (BFG all terrains) all help the rotational mass and rolling resistance. I also did dual electric fans on this swap, and I have a sharp custom tune in it using HPtuners and a wideband. That's the sweet part with this EFI, you can fine tune the fuel tables as well as a few other little tricks. Alot of my gas mileage with this rig is in the tune.

You can get upper teens in these old trucks with a carbed 350 using alot of these tricks and a sharp tune, with the right gearing and tire size. But it's going to cost money to do it. Whether it's worthwhile is up to you. That depends on what you plan with the truck, and how long you are going to keep it.