8.5 mpg

[MattyICEx51]

Okay so I have a question. I have an 83 Scottsdale and I'm getting 8.5 mpg it's my daily driver. I drive mostly highway and a little off road during hunting season. It has an old crate GM 350 put in a few years ago by the previous owner with a Q-jet carb. I'm thinking of putting on an edelbrock 1406 carb / 2701 intake manifold, new plugs / wires, hooker headers / exhaust. What other things should I do to help my mpg and performance. I am still new to mechanic work so I'm trying to learn as much as I can. Thank you for you help and time.

 

[Georgeb]

I would try to stay with the Qjet for mileage. Please share more details about your rig. Tire size, axle ratio, trans type, initial timing and any other detils you can.

 

[PrairieDrifter]

No edelbrock. lol

 

[Georgeb]

I had an edlebrock I loved but it took a bit of tuning. It was not a good mileage carb tho. Heck that truck wasnt meant for getting good mileage.
The Qjet is your best bet for mileage.

 

[Green79Scottsdale]

With an '83 you should have a TH350 or TH400. If you do mostly highway runs, your engine could be running around 3k rpm. This will kill the MPG, especially due to the non-aerodynamic nature of our trucks. Doing a good tune up (wires and plugs) certainly won't hurt. Freeing up the exhaust with headers and new pipes would probably help too. I would hold of on the carb as stated, but if you have the funds, an intake would be the last thing from your stated list. Of course, the Q-Jet should be looked at and made sure it is running properly along the way.

My truck gets 10 mpg. 400 sbc, TH400, 3.73 gears, 31 inch tires, stock motor.

 

[HotRodPC]

As Bob pointed out. No Aerodynamics and the weight hurt our trucks.

But have you done an odo test and KNOW that your odometer is accurate? Maybe it's reading slow and you're ACTUALLY doing better than your math will show. My 454 C20 with a Th400 and 3.21's got 9 - 13.2 mpg. I now have 3.42's in the rear and no difference. I have a feeling if I dropped to 3.73's and for sure with 4.10's I'd gain a hair in the city mpg but I'd lose drastically on the highway.

 

[1987 GMC Jimmy]

Since you're doing highway driving, you might consider getting a gear vendor, which will split the gears in your three speed up to six. A good, remanufactured 700r4 will be just as good and more authentic if you're willing to spend that much. Keep the Quadrajet, though.

 

[Quadrajet Power]

The quadrajet is designed for best fuel economy, and performance. Yours may need to be built to fix issues from wear and age. But it will be your best option.

As mentioned, good tune, exhaust flow and fresh quadrajet would possibly help you on mpg's.

 

[rich weyand]

Keep the Qjet, but make sure the well plugs aren't leaking gas and the throttle plate pivots aren't leaking air.

Time the distributor correctly, connect the vacuum advance to manifold vacuum, run good 8mm solid-conductor wires (like Taylor 74206), run ACDelco R45TS or Autolite 24 plugs with .045" gaps.
http://www.gmsquarebody.com/forum/showthread.php?p=293806

I am running an Edelbrock 1406 on a dual-plane manifold with Hooker headers and duals, on a K10 (extra spinny stuff underneath), and I get 10 mpg in town, 12 mpg on the highway at 60, and 10mpg at 75 with a TH350 and 31" tires on 3.73:1 axles.

The Qjet should do slightly better than that. 2WD should do better than that.

You can put the Qjet on a 2101 dual-plane manifold. You can also get the Qjet rebuilt, or get one built for your setup, from SMI carbs. Sean Murphy knows his stuff.

I would be running a Qjet, but the 1406 was on it when I got it, and it's OK. Not enough difference to make me pay to change it out. But if you have the Qjet already keep it. Rebuild it, but keep it.

 

[rich weyand]

Oh, since it's a pollution-era truck, change out the vacuum advance can for an AR23/VC1853.

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=ECHVC1853_0168367499

The pollution-era vacuum cans are not correct for a non-emissions crate engine.

 

[Georgeb]

What Rich said.

 

[Rusty Nail]

I wanna join on the q-jet wagon but I'm not gonna.
Seems likely that any type of well maintained, properly functioning , and in-tune carburetor could out perform one that isn't.
That being said , and at risk if sounding like a broken record to some, my opinion is to work with what you already have at minimal cash outlay.
Upon satisfaction that your truck is in prime mechanical condition, likely the next step will make itself known to you.

Fix what is there rather than ignore the foundation while adding unproven parts.

It's an EIGHTY THREE. It's has been doing something right all this time! Throwing parts at it will NOT fix it. No amount of butter or yummy jelly will unburn the toast.

Vacuum hoses, intake seal,carb gaskets, egr passages are some of the first things EYE would look at. Intake gasket set is CHEAP. Loads of fun can be had taking all that stuff apart, cleaning,spraying it, new hoses....it's rewarding. Spend some time with it . Got 20 bucks?

Good luck!

 

[Georgeb]

I wanna join on the q-jet wagon but I'm not gonna.
Seems likely that any type of well maintained, properly functioning , and in-tune carburetor could out perform one that isn't.
That being said , and at risk if sounding like a broken record to some, my opinion is to work with what you already have at minimal cash outlay.
Upon satisfaction that your truck is in prime mechanical condition, likely the next step will make itself known to you.

Fix what is there rather than ignore the foundation while adding unproven parts.

It's an EIGHTY THREE. It's has been doing something right all this time! Throwing parts at it will NOT fix it. No amount of butter or yummy jelly will unburn the toast.

Vacuum hoses, intake seal,carb gaskets, egr passages are done if the first things EYE would look at. Intake gadket set is CHEAP. Loads of fun can be had taking all that stuff apart, cleaning,spraying it, new hoses....it's rewarding. Spend some time with it . Got 20 bucks?

Good luck!

Huh? Whats all this mean?

 

[Gryphon78]

Also check for the start of an sort of fuel leak. My 86 c20 305 700r4 3.73 31"tires. Was doing like 5mpg and found out gas tank was leaking but it was almost unnoticeable.

 

[Rusty Nail]

Lol? What do you mean, what does it mean? It means what it means. I reread it, seems pretty clear to me although I fixed a pair of typos.

The gas leak suggestion us a great idea. I think often these trucks leak gas. The undercarriage lines are rubber...