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more mpg out of suburban

B

black dawg

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In our family car burb (91 1500 4x4) I have been thinking about building a small cube v8 to try to help mpg. The thing is rarely driven on the highway and gets about 11 usually. With 3.73s and stock tires it feels like it could get around with alot less motor.

anybody have any experience with something like this?
My first thought was build a tbi 292 six banger, but always hear that they were lousy for mpg. I dont know if a 4.3 or a 250 would be enough motor, but somewhere in the 283-307 range seems like it would be ok.

the plan would be to keep it tbi.
 
You aren't going to gain enough to make it worth it.

Hate to be blunt....

Stepping up to a new LS 5.3 might help a little, but really doubt it would be worth the cost/hassle.

Factor in how much gas you can buy for the conversion cost before oyu make a final call...
 
If you're on the western half of the state, a smaller engine would be a dog going up the mountain passes like the one outside of Butte for example.
What about converting your Sub to a diesel? With a 6.2 you could probably get into the high teens, low 20's no problem.
 
dhcomp said:
You aren't going to gain enough to make it worth it.

Hate to be blunt....

Stepping up to a new LS 5.3 might help a little, but really doubt it would be worth the cost/hassle.

Factor in how much gas you can buy for the conversion cost before oyu make a final call...
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the way I am looking at it is this, the burb has 165k on it now and the way it is being used will probably need a motor in 50k anyway. I have a use for the tbi 350 that is in it now, so it would just be the cost to build the small v8. I am not an expert with tbi tuning, but I would bet a 305 prom would work for one of these motors.
 
snuffy74 said:
If you're on the western half of the state, a smaller engine would be a dog going up the mountain passes like the one outside of Butte for example.
What about converting your Sub to a diesel? With a 6.2 you could probably get into the high teens, low 20's no problem.
Click to expand...


the diesel would fix the mpg issues for sure, but I have had enough of the old 6.2-6.5 motors that I just dont trust them any more. And the tbi motor has a huge driveability/startability advantage.
 
go 2wd and drop it down to about 6" off the ground, had a friend drive a Burb from Phoenix to Dallas area Texas, (lowered at the time) got pretty awesome mileage for a bigger truck, guessing the lack of wind turbulence under the truck helped out a ton.

My Burb when it was stock, 350TBI/700r4 & 3.42 gears would get about 14-15 on the highway, as soon as I lifted it, the mileage dropped, Maybe 12 now. :/

My mothers '94 Silverado 2wd pickup has a 4.3 in it, it really does suck for city street driving, it gets the job done, but doesn't really do much better on mileage around town than my Burb does, now on the highway it did do pretty well from Phoenix to Indiana, if I remember what we figured, it was in the low 20's
 
if built for low rpm torque with lower highway gears you could get much better mpg with your 350 and they are cheap to rebuild. I would stick with the 350 and expect 16-17 fairly easy. been known to get 19+ out of em in a burb. :waytogo: would be a enjoyable driver as well.

BTW if fuel pains you now, your in for a real hurting :eek1: sad but true.
 
Bang for your Buck - dropping gears would probably help more than an engine swap. Look around and see where you can get rid of weight, too. A diesel conversion is the only major MPG changer. You should get a couple MPG with a 5.3 swap, but keep in mind that gas is still relatively cheap. If you spend $2k for an engine swap and go from 11MPG to 13MPG, it takes 41,000 miles to hit your break even point (at $3.50/gallon)
 
bailey9r said:
if built for low rpm torque with lower highway gears you could get much better mpg with your 350 and they are cheap to rebuild. I would stick with the 350 and expect 16-17 fairly easy. been known to get 19+ out of em in a burb. :waytogo: would be a enjoyable driver as well.

BTW if fuel pains you now, your in for a real hurting :eek1: sad but true.
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Who gets 19+ from a gas square nose Suburban?
 
x2... I never heard of anywhere near 19 mpg from a 73-91 bodystyle...

Suburbans are heavy and use alot of gas around town. My '98 gets 17mpg highway all day long, but 12mpg city. no way around it that I know of.
 
6BT

tho I've never seen the 4's in a vehicle, I've certainly seen my share in boats... I would be suspect of a 4 as far as power goes in a burb.... you'd get 20 easy out of a 6 and plenty of power..
 
ryoken said:
6BT

tho I've never seen the 4's in a vehicle, I've certainly seen my share in boats... I would be suspect of a 4 as far as power goes in a burb.... you'd get 20 easy out of a 6 and plenty of power..
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a couple years ago I worked on a ford crewcab 4x4 that had a 4bt. It was slightly bombed and the power was very surprising. talking out my ass here, but I would wager it was around 425-450 ft lbs.
 
could be.. I've never worked on any other than stock marine ones...
 
6 by would be sweet! But the cost of the engine and adapters, plus the fab work involved would be greater than any cost savings on fuel I would think.

Sent from my HTC Sensation 4G using Tapatalk
 
GMCSuburban2500 said:
x2... I never heard of anywhere near 19 mpg from a 73-91 bodystyle...

Suburbans are heavy and use alot of gas around town. My '98 gets 17mpg highway all day long, but 12mpg city. no way around it that I know of.
Click to expand...

I don't recall saying anything about city vs highway, but my buddy had a 76ish (maybe up to a 78 I don't recall) and it got fairly good mpg and we put an rv (crane HT) cam in it, and a couple of other things, thinking it would help towing, anyway afterwards he got 19 mpg all day long when not towing his camper. In those days the burb was king of bumper pull towing. It wasn't a 40 inch ground hawg 4*4 setup BUT IT WAS SQUARE AS THEY COME. :dunno:whoops damn cap locks. :thumb:
 
bailey9r said:
I don't recall saying anything about city vs highway, but my buddy had a 76ish (maybe up to a 78 I don't recall) and it got fairly good mpg and we put an rv (crane HT) cam in it, and a couple of other things, thinking it would help towing, anyway afterwards he got 19 mpg all day long when not towing his camper. In those days the burb was king of bumper pull towing. It wasn't a 40 inch ground hawg 4*4 setup BUT IT WAS SQUARE AS THEY COME. :dunno:whoops damn cap locks. :thumb:
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I really doubt a square carb'd burb got that mileage. Lots of people's speedo's are off...especially in that age, when there was no way to verify via GPS>
 
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