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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/
Location: We_tside PNW (Columbia Gorge) / CO / SA TX / Thailand
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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
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.
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.
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.
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.
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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