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Eric 1
03-24-2004, 01:07 PM
Well i was checking my mpg on my truck this week and it is about 9-10 mpg!!! now it has a 350 with headers heads and edelbrock carb and intake with a 3 speed auto and stock rear end. is this about right or is there something i can do to make it better. It is expensive to drive man!!:eek:

Davis Lawn Mowing, LLC.
03-24-2004, 01:24 PM
Hell, I am looking at the same model. 1500 Extended Cab 5.8 350. Bronzish-gold, almost tan, tan leather interior, bedliner, matching fiberglass topper, power everything ecept seats and 98,000 miles for $9700. I think I can talk the guy down to an even 9 grand though. I hope it gets better gas mileage than that though.

Lawn Specialties
03-24-2004, 01:37 PM
I have a 92 Gmc extended cab 4x4 with a 350 and it gets 12-13 pulling my trailer in town.Fuel injection makes a huge difference over a carb.

twins_lawn_care
03-24-2004, 02:54 PM
Eric, that sounds a bit low, maybe there is some adjustment to be made on your carb?
is this while in tow, or any other info you can let us know about.
Sounds like it should be a little higher than 9-10. Now I see why you are looking to swap your rear end out, but that may not be the problem. With the lack of power you seem to be having, and this MPG problem, it may need some tuning up?

The Captain
03-24-2004, 04:52 PM
Just thought I'd get my nickles worth in....I've got a '95 1500 w/ 175k miles on a 350 V-8 w/ extended cab, 8' bed w/fberglass shell. First of the month I hauled my Turf Tiger, on a 16' single axle, from Little Rock to St. Louis and got 13-14 mpg on the highway. I tried two ways of checking the mpg. One tank I set the tach on 1900 rpm (65 mph+/-) and the other fillup I ran 70+ mph. There was no noticeable difference. I think it's the nature of the beast when they're working. If anyone can squeeze more mpg let us all know. (Unleaded regular went to $1.85 last night in the St. Louis area.) Did you ever wonder why they do it, raise the prices at night?

Eric 1
03-24-2004, 09:03 PM
Originally posted by twins_lawn_care
Eric, that sounds a bit low, maybe there is some adjustment to be made on your carb?
is this while in tow, or any other info you can let us know about.
Sounds like it should be a little higher than 9-10. Now I see why you are looking to swap your rear end out, but that may not be the problem. With the lack of power you seem to be having, and this MPG problem, it may need some tuning up?

Lets see,
That figure is in tow in town and also not towing, there seems to be very little differance.
The carb is new but it may be slightly out...not that much.
Need a tune up, no the motor is new only about 5-6k on it.

Eric 1
03-24-2004, 09:05 PM
Captain, You say you get 13-14 on the highway...what about in town.

The Captain
03-24-2004, 10:06 PM
I've not really checked the mpg in town or city traffic. (I'm really kind of afraid to, now that we've been talking about it.) Just a good guess based on three years would put it at about 11 or 12. Last July I ran to Orlando with the truck empty except for me and 1 suitcase and got about 16.5 as an average for the two thousand +/- mile trip.
I don't think with the rear end ratios in these 3/4 tons we will see much more. With gas prices headed where they seem to be going I wish we could find that secret tune-up.

YardMeister
03-24-2004, 11:21 PM
I have a '92 GMC Yukon 4X4 with the 350 in it. It gets 18 mpg hiway when empty on a trip usually running around 65 mph, 13 mpg around town pulling my 3k-pound trailer, and average around 15 mpg most of the time for my mix of work and personal driving. It is fuel injected, has the automatic with overdrive, and the higher ratio rear-end. I do wish it had better low-end pull, but having better gas mileage is the trade-off. I’ve used “Mobile 1” synthetic oil in it, since new, and run synthetics in both differentials, the transfer case, and the transmission. It now has 129k miles, and still runs like new. I really enjoy this truck.

twins_lawn_care
03-25-2004, 03:19 PM
Eric,
Even though the carb is new, it may not have had the correct adjustments on it when it was installed (just a guess, and trying to help fix the problem with lowest possible $ for you)
I'd just double check the idle/mix screws, and float level, should take about 10 minutes, and then you can rule that out, and go from there. Also, possibly double check your timing. You could be blowing a lot of unused gas out of your exhaust, which could be a reason for the low MPG and lack of power.
Just trying to help out with where I'd start. I'd tend to think though with your set up, you should be getting around 13-16 mpg though, as others had mentioned.
Something to think about though, is to just take it in for a gas analyzer test at a local carb shop. May cost about $50, but with the prices of gas now, you could easily save that by boosting your MPG up from 10!
Good luck with it, and let us know if you figure it out.

Eric 1
03-25-2004, 06:10 PM
Originally posted by twins_lawn_care
Eric,
Even though the carb is new, it may not have had the correct adjustments on it when it was installed (just a guess, and trying to help fix the problem with lowest possible $ for you)
I'd just double check the idle/mix screws, and float level, should take about 10 minutes, and then you can rule that out, and go from there. Also, possibly double check your timing. You could be blowing a lot of unused gas out of your exhaust, which could be a reason for the low MPG and lack of power.
Just trying to help out with where I'd start. I'd tend to think though with your set up, you should be getting around 13-16 mpg though, as others had mentioned.
Something to think about though, is to just take it in for a gas analyzer test at a local carb shop. May cost about $50, but with the prices of gas now, you could easily save that by boosting your MPG up from 10!
Good luck with it, and let us know if you figure it out.

Yes i thought i should get at least 12 mpg. I will check those things you mentioned tomorrow.Thanks

FrankenScagMachines
03-26-2004, 07:19 AM
Don't feel bad- I get 9 or 10 in town with a trailer and 12 on highway empty. Bout 11 on highway with trailer. Maybe 12.5 empty on interstate. Best I ever got was highway empty that was 13.5 mpg! This is fuel injected too. Dual exhaust as well (if that's supposed to help.) Man these old Ford's pass anything but a gas station! I have a 5 spd stick and a 3.55 rear end under it. 2wd. 3/4 ton. 351 Windsor EFI. My mileages seem similar to other guys at a Ford truck forum...

The Dude
03-26-2004, 12:45 PM
I have a carbed 302 in my 1979 Ford truck and I get an average of about 8. I get only about 160 miles to a tank of gas, that sucks.

jlewis
03-26-2004, 01:29 PM
Eric,
That is why I was happy to come across my deisel!

I am averaging 16. Empty, towing, in town, 70mph does not seem to matter much. I am getting some Stanadyne fuel additive so I will see if that helps any. (Claim it does) I am also switching from 215/85 to 235/85/16 tire tonight (6 Yikes!). With 4.10 gears she is maxed at 70!

Joe

Trevors Lawn Care
03-27-2004, 06:36 PM
New 2000 GMC SIERRA gets about 11. ITS SUCKS. i just upgraded from a buick lesabre which got 20. although that was the first tank i tested it on, and i drove it less than efficient. I was still getting used to the V8

Eric 1
03-27-2004, 10:26 PM
Well at least i know i'm not alone. I played with the carb and timing some we'll see what happens.

Oh yeah i ordered a cam two. comp cams 440 lift, called them and this is what they said to get i also order a ''swirl port'' carb spacer and some fancy gaskets that the people at Jegs said would help some so when i get it all done i will let you know what happened.

BillyRgn
04-07-2004, 11:19 AM
95 gmc 3500 350motor 9mpg's on a good day

bugspit
04-07-2004, 11:32 AM
Eric 1,
Whats the rear end gear ratio?
If your using a 4barrel carb, swap to a large 2barrel.
Why not go with fuel injection?
It sounds like you are putting a lot of preformance mods on it, what are you expecting, preformance or economy?

T-Time
04-07-2004, 12:47 PM
Have you thought about the convertor being restricted, this can make a difference.

Mitch

Eric 1
04-07-2004, 08:54 PM
Originally posted by T-Time
Have you thought about the convertor being restricted, this can make a difference.

Mitch

Straight duals baby...no converter.Don't tell.

Bugspit
1.I dont know what the rear axle is all i know is i read on the net that those trucks have between 2;73-3;10 in them.If you saw my other thread you will see i am about to swap my rear end.
I will be installing 3;73 and in a month or so installing an overdrive trans in it so when i am not towing i can put it in overdrive and get some economy out off it.
2.Why should i go to a 2 barrel carb, man talk about gutless.
3.Yep i am installing lots of performance parts, i an trying to find that fine line of both economy and performance.
4.I looked into a fuel injection system from holly for a non ecm engine but it is $780, thats more than i want to spend on something like that for so little gain i would get from it.

bugspit
04-07-2004, 09:08 PM
Call a 2barrel gutless but, I once had a chevy 350 in a stepside, 4speed with a granny 1st gear. It also got 8-10mpg until I swapped the 4barrel holley to a 2barrel, started getting 12-14mpg. I believe my best was 16mpg at 55mph on a interstate trip. It also had headers and dual Cherry Bombs (opps,that dates me).

I think it had a 3.73 gear, maybe 4.10 not sure.
The OD tranny should help.