Better gas mileage - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Clyde65** · 03-22-2011, 09:54 AM

Quote:

Originally Posted by roofingbloke

Hi guys, good topic,

Just thought i would mention that petrol in the UK is £1.40 per litre,

But you cannot put a price on the smile you get on your face when you drive a classic car/truck.

Wow! thats over $9.00 a gallon US!

Would we drive our trucks if fill ups cost $180.00? YOUR DARN RIGHT WE WOULD!

*stich626* · 03-22-2011, 11:33 AM

find a 3.08 rear gear and install it, or change out the whole rear if easier than setting up gears..
those 4.56 are killing you..

Longhorn Man · 03-22-2011, 04:41 PM

getting a 3.08 gear would be a pain and then you start getting into fab work since it would most likely be a 14 bolt later model rear.

**Clyde65** · 03-22-2011, 05:22 PM

I have a 3.07/8 in my 12 bolt 72 rear.

NONHOG · 03-22-2011, 05:48 PM

Couple of thoughts here.
Breathing is a factor maybeif you keep the high # gears.
The easy way to get better mpg is to lower speed. Engine and vehicle.
If your engine speed (rpm) is down better breathing wont mean much as it breaths plenty at low rpm's.

Aero gains should be considered, like LHM said about holding your hand out the window at speed. Try holding a truck mirror vs. a sport mirror.
Bed cover, Grill block, narrow tires?, vac gauge.

Take a look here.... http://ecomodder.com/forum/fuel-econ...ifications.php

There are a few truck guys on that site. Some of there ideas work but I wouldn't do them. Engine kill switch, teeny tiny car.
Some good ideas.

**'68OrangeSunshine** · 03-22-2011, 06:53 PM

Quote:

Originally Posted by Longhorn Man

Since I do not know much about inlines, I would recomend looking into it more before laying down the cash for expensive inline parts. The header could help with low end torque and actually help, or it may just be money spent that you won't see improvements on.
If you are looking to make power, then go for it, but for higher MPG, do some more research. I think there's an inliners forum that would be ideal for your questions.

Hey Andy, That's: www.inliners.org

Longhorn Man · 03-22-2011, 10:37 PM

Quote:

Originally Posted by Clyde65

I have a 3.07/8 in my 12 bolt 72 rear.

You have a half ton, he has a 3/4 ton. Since there's been no talk of making his a 1/2 ton truck, I can only assume he has no interest in a 12 bolt rear. If he is willing to do a suspention swap, then yes, a 3.07 (3.08 was a car gear) 12 bolt would be the way to go.

Quote:

Originally Posted by '68OrangeSunshine

Hey Andy, That's: www.inliners.org

inliners.org... that's the one I was thinking of... thanks for the link!

D13 · 03-23-2011, 07:24 AM

3.42's in 14bolt SF, 8 bolt 16/16.5, any light 3/4 ton. That's how the 81 above was set up, and I could make it get 15's pretty easily. Taller tires would help, I was running about 31's.

3.23's were an option but rare.

Clifford will hurt your mpg (it's more of an RPM manifold) but the headers should help slightly.

It's those rear gears that are the killer. Which axle do you have, 12 bolt or Eaton?

Junkpyl · 04-15-2011, 07:51 PM

I'm running half ton gear and I believe 3.42's with a 2004r overdrive automatic.

treeboy97 · 05-02-2011, 08:57 AM

Did a test this weekend, 130 miles and ended up with 17.5 MPG.

Installed the Astro Van T5 over the winter and this was its first long drive. Very happy. I have the pertronix upgrade next to install. Plus have a new intake, split longtube headers and a Holley four barrell on the shelf in waiting

Currently I have a stock intake, carb, exhaust and 3.73 gears.

Junkpyl · 05-02-2011, 07:52 PM

That sounds respectable. I have kinda the same setup as you except with an auto trans. Just purchase a new HEI and wires for it. Keep us updated as you upgrade to your aftermarket goodies on whether the mileage goes up or down. I'm still plugging along trying to put mine together. All this rain needs to stop before I can proceed any further.

soxplayer · 05-16-2011, 10:39 AM

My 2 cents (possible 3 cents at todays gas prices). Keep your speed down. I can get 14 MPG on the highway with a 250, 4 speed and 5.13:1 gears in a 67 C20 with the old model B carb. I have to run 60 with the engine turning over at 3500. The truck is running on the rich side with factory jetting and it has an old LMC glasspack single exhaust. Otherwise it is stock including the ignition system. Tall gear will help but you are fighting bad aerodynamics and a small engine for the load. If you gear too tall you will spend a lot of time with the powervalve open in the carb (yes even a model B has a power circuit) and your gas mileage will go away unless you are driving on flat ground with a tailwind.

03-22-2011, 11:33 AM	#27
stich626 Account Suspended Join Date: Sep 2010 Location: hingham ma Posts: 1,721	Re: Better gas mileage find a 3.08 rear gear and install it, or change out the whole rear if easier than setting up gears.. those 4.56 are killing you..

03-22-2011, 04:41 PM	#28
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Better gas mileage getting a 3.08 gear would be a pain and then you start getting into fab work since it would most likely be a 14 bolt later model rear.

03-22-2011, 05:22 PM	#29
Clyde65 1965 Chevy C10, 2005 4.8L/4l60 Join Date: Aug 2004 Location: DFW Texas Posts: 8,541	Re: Better gas mileage I have a 3.07/8 in my 12 bolt 72 rear. __________________ Clyde65 Rebuild of Clyde http://67-72chevytrucks.com/vboard/s...84#post8338184 69 Aristocrat Lo Liner build http://67-72chevytrucks.com/vboard/s...84#post7561684 *support our troops!*

03-22-2011, 05:48 PM	#30
NONHOG Registered User Join Date: Feb 2007 Location: Marana, Arizona Posts: 3,416	Re: Better gas mileage Couple of thoughts here. Breathing is a factor maybeif you keep the high # gears. The easy way to get better mpg is to lower speed. Engine and vehicle. If your engine speed (rpm) is down better breathing wont mean much as it breaths plenty at low rpm's. Aero gains should be considered, like LHM said about holding your hand out the window at speed. Try holding a truck mirror vs. a sport mirror. Bed cover, Grill block, narrow tires?, vac gauge. Take a look here.... http://ecomodder.com/forum/fuel-econ...ifications.php There are a few truck guys on that site. Some of there ideas work but I wouldn't do them. Engine kill switch, teeny tiny car. Some good ideas. __________________ "I feel the need for speed!"... as soon as I am done with my nap.

03-23-2011, 07:24 AM	#33
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: Better gas mileage 3.42's in 14bolt SF, 8 bolt 16/16.5, any light 3/4 ton. That's how the 81 above was set up, and I could make it get 15's pretty easily. Taller tires would help, I was running about 31's. 3.23's were an option but rare. Clifford will hurt your mpg (it's more of an RPM manifold) but the headers should help slightly. It's those rear gears that are the killer. Which axle do you have, 12 bolt or Eaton? __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors Last edited by D13; 03-23-2011 at 07:28 AM.

04-15-2011, 07:51 PM	#34
Junkpyl Registered User Join Date: Jan 2007 Location: Scottsdale Arizona Posts: 125	Re: Better gas mileage I'm running half ton gear and I believe 3.42's with a 2004r overdrive automatic.

05-02-2011, 08:57 AM	#35
treeboy97 Registered User Join Date: May 2009 Location: Waynesville, Ohio Posts: 136	Re: Better gas mileage Did a test this weekend, 130 miles and ended up with 17.5 MPG. Installed the Astro Van T5 over the winter and this was its first long drive. Very happy. I have the pertronix upgrade next to install. Plus have a new intake, split longtube headers and a Holley four barrell on the shelf in waiting Currently I have a stock intake, carb, exhaust and 3.73 gears. __________________ 1970 C10 LWB (Grandfather's Truck) 5.3 4L60E 2012 Victory Cross Country Touring I'm not wasting money on my truck/bike, I'm helping to rescue the economy one mod at a time.

05-02-2011, 07:52 PM	#36
Junkpyl Registered User Join Date: Jan 2007 Location: Scottsdale Arizona Posts: 125	Re: Better gas mileage That sounds respectable. I have kinda the same setup as you except with an auto trans. Just purchase a new HEI and wires for it. Keep us updated as you upgrade to your aftermarket goodies on whether the mileage goes up or down. I'm still plugging along trying to put mine together. All this rain needs to stop before I can proceed any further.

05-16-2011, 10:39 AM	#37
soxplayer Registered User Join Date: Jun 2009 Location: Forest City IA Posts: 56	Re: Better gas mileage My 2 cents (possible 3 cents at todays gas prices). Keep your speed down. I can get 14 MPG on the highway with a 250, 4 speed and 5.13:1 gears in a 67 C20 with the old model B carb. I have to run 60 with the engine turning over at 3500. The truck is running on the rich side with factory jetting and it has an old LMC glasspack single exhaust. Otherwise it is stock including the ignition system. Tall gear will help but you are fighting bad aerodynamics and a small engine for the load. If you gear too tall you will spend a lot of time with the powervalve open in the carb (yes even a model B has a power circuit) and your gas mileage will go away unless you are driving on flat ground with a tailwind.



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