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Old 05-19-2012, 01:41 PM
 
Location: New Orleans, LA
1,809 posts, read 4,924,243 times
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Old 05-19-2012, 04:44 PM
 
Location: My little patch of Earth
6,193 posts, read 5,137,491 times
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Of course.........depending on how it is equipped already (we have none of that info), I'd suggest:

1. Changing the rear gear ratio to 3:08 or 2:90 if you find them

2. Make sure the tranny has overdrive

3. Add a superchip tuned for economy

4. Do frequent maintenance on the engine

5. Install a smaller engine combination
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Old 05-19-2012, 06:32 PM
 
Location: Earth
4,237 posts, read 23,640,392 times
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Not sure how much better mpg you want, but those trucks are tanks and guzzle gas, plain and simple. My ex g/f's mom and dad had one...a 1981 model....with the 305 engine...her mom said it only got 11 mpg. I'm sure it weighed in excess of 5000 lbs too. I don't recall what transmission it had...probably a TH350 if I had to guess...since I don't believe the 700-R4 4 speed overdrive was avaliable until the following year.

Anyways how many mpgs is the truck getting now? What all has been done to it if anything/
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Old 05-19-2012, 08:34 PM
 
Location: San Antonio, TX USA
5,250 posts, read 12,514,676 times
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You have a big motor in a vehicle that weighs more then the moon. Its not going to get much better then 10-12 mpgs
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Old 05-21-2012, 01:05 AM
 
Location: We_tside PNW (Columbia Gorge) / CO / SA TX / Thailand
30,435 posts, read 50,679,622 times
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Suburban is a fairy common platform to get a Cummins Diesel Transplant from a Dodge. (that would be a 'few parts', but you can get donor vehicles for ~ $2000)

With correct gearing, that engine will give you 18-22 mpg for about a million miles (and for fuel; you can use free fryer grease, Jet A, Heating oil, Bio diesel, used engine oil, veggie oil, ....)

I get 20 mpg in my 4x4 dually Dodge cummins and it weighs 8,000# and I often cross the scales at 30,000# with a load (bulldozer and trailer). It only gets 12 mpg when towing that heavy.

VW-D... 50 mpg since 1976, no Dinosaurs or OPEC required
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Old 05-21-2012, 06:25 AM
 
Location: H-town, TX.
3,503 posts, read 6,936,158 times
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Heads, cam, valve work, something better than TBI to dump fuel in the engine. I swear when the LS1 was in its infancy, there was a mag write-up that had a Vette getting ~40 MPGs.

That's the bad thing about that era SBC. The top end flows pretty badly and it falls on its face pretty quickly as a result. A pretty bum deal for about 200 horsepower.

I'm guessing you ain't putting a Cummins on a 1/2-ton, though the 6.2L diesel was available that year from GM. Would be a lighter engine to drop on that front end. I don't see 2.73 gears working for you, since that engine will gurgle gas just to get that ride moving.
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Old 05-21-2012, 11:20 AM
 
Location: U.S.A.
3,306 posts, read 11,330,694 times
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There are lots of things you can do... get an overdrive trans (4L80E), get an overdrive kit for existing trans, upgrade to a multiport FI setup (megasquirt), change rear-end gearing, throw in a cummins 6BT... etc. All of the above are a lot of work and a lot of money. You would probably never see the savings in fuel costs vs. what you invested in the upgrades, not even including the time. In other words you're probably better off leaving it as is.
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Old 05-21-2012, 02:11 PM
 
Location: Eastern Washington
16,139 posts, read 52,827,997 times
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First things first - make it work right in stock form, before you start modding - make sure the truck is in good tune, if it can use plugs, I rather like NGK, if this is a conventional SBC, orient the plugs such that the ground electrode points more or less at the intake valve, for FI, the fuel filter is more important than the air filter in terms of MPG. When you need tires, consider a low rolling resistance tire (keep in mind, you don't get anything for free, LRR tires are not for everybody).

You could do things like an MPG oriented cam, etc, but at some point it makes more sense to reserve the big truck for jobs only it can do, and find an economical car for daily use. Lux is right, you can easily spend money on MPG oriented mods that you will not make back in gas for a long time.
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Old 05-27-2012, 01:25 PM
 
Location: New Orleans, LA
1,809 posts, read 4,924,243 times
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Quote:
Originally Posted by Deez Nuttz View Post
Not sure how much better mpg you want, but those trucks are tanks and guzzle gas, plain and simple. My ex g/f's mom and dad had one...a 1981 model....with the 305 engine...her mom said it only got 11 mpg. I'm sure it weighed in excess of 5000 lbs too. I don't recall what transmission it had...probably a TH350 if I had to guess...since I don't believe the 700-R4 4 speed overdrive was avaliable until the following year.

Anyways how many mpgs is the truck getting now? What all has been done to it if anything/
This past week I had flushed out the old motor-oil with 2 bottles on Engine Flush and put in some new motor-oil. Castrol GTX High Mileage 10W40.

Along with putting in a new oil-filter from Fram which is the top model silver-colored one.

Added a new air-filter from K&N and used a whole big bottle of Lucas Fuel Injector cleaner.
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Old 05-27-2012, 03:22 PM
 
Location: Earth
4,237 posts, read 23,640,392 times
Reputation: 2260
Quote:
Originally Posted by Blackandgold51 View Post
This past week I had flushed out the old motor-oil with 2 bottles on Engine Flush and put in some new motor-oil. Castrol GTX High Mileage 10W40.

Along with putting in a new oil-filter from Fram which is the top model silver-colored one.

Added a new air-filter from K&N and used a whole big bottle of Lucas Fuel Injector cleaner.
The air filter will help mpgs improve, not by much.
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