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Old 05-13-2010, 08:01 AM   #1
grinch4om
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engines and mileage

gas is killing me! This big block is fantastic but gas....13 MPG ish...what are your experiences with 350's? my 305 in this same truck got 13-14 and wouldn't pull your hat off your head. Now I slap curbs but what about an in between engine? comments please....
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Old 05-13-2010, 08:55 AM   #2
bigdnew
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Re: engines and mileage

go gen III. either the 5.3 or the 6.0.
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Old 05-13-2010, 09:22 AM   #3
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Re: engines and mileage

If you are getting that kind of mileage out of a 454, you should be thrilled. The one in my '73 averaged somewhere around 6 MPG, and the one in my '75 Blazer was probably closer to 4. Of course, neither was built to be a daily driver, either.

My '87 SWB with a stock TBI 350 averaged around 17 with a 700R4 and 3.42 gears, as a comparison.
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Old 05-13-2010, 09:30 AM   #4
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Re: engines and mileage

Quote:
Originally Posted by bigdnew View Post
go gen III. either the 5.3 or the 6.0.
Go this route and you will not be disappointed! Good power, good mileage, and the always important Coolness Factor.
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Old 05-13-2010, 09:43 AM   #5
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Re: engines and mileage

13 mpg out of a big block, I would be doing backflips.
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Old 05-13-2010, 09:49 AM   #6
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Re: engines and mileage

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Originally Posted by Edgel82c10 View Post
13 mpg out of a big block, I would be doing backflips.
+1!!!!

The 5.3 in my 2001 tahoe has only pulled better than 14mpg once, and that was going down hill with a tailwind.
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Old 05-13-2010, 09:57 AM   #7
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Re: engines and mileage

My partial gas mileage history:
73 C20 454, TH400, No A/C - 10-11 mpg city - 13 hwy
76 C20 350, TH350, A/C - 9-10 mpg city - 13 hwy
83 C20 454, 4 Spd granny, gear vendor, A/C - 11 mpg city, 13-15 mpg hwy

Big old pickups, especially 3/4 ton, don't get good gas mileage, unless you go to 1/2 ton V6 stick, then I have seen/heard of 18/22 mpg.

Newer pickup gas mileage history:
2000 Silverado V6 auto - 18-19 mpg. city, 22-23 mpg hwy
2003 Sierra ext. cab, 5.3 auto - 17-18 mpg city, 22 mpg hwy.
All above vehicles were driven like grandma on her way to church, not like a teenager.

Modern pickups can routinely get 17 mpg. city when driven carefully, whether diesel or gas. That's about it.

While this is not popular on this forum, if you don't need to drive a truck on a daily basis, a truck is a bad daily driver (based on fuel economy only, which is the basis of your post.) Having said that, I won't get rid of my old 83 beater pickup (second vehicle) any time soon, especially since it has a handy stealth dump bed.
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Old 05-13-2010, 12:25 PM   #8
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Re: engines and mileage

My 86 swb with a 305 and 700r4 with a 2.73 rear gets 17-18 mix of city highway but has no balls, I wish I had a BBC knockin back 13!
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Old 05-13-2010, 02:58 PM   #9
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Re: engines and mileage

i get about 10 in my 1 ton. with a carb that's tired. what kills me is the turbo 400 on the highway engine screams! If you do a 5.3 or 6.0 swap even though you can have 300hp easily by the time you make up the difference in cost it will take you forever. But it would be way cool to have a 5.3 or 6.0! not dissing people that have them. I would like to do a cummins conversion to mine or 6.0. with a nv4500.
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Old 05-13-2010, 03:19 PM   #10
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Re: engines and mileage

84 c10 305/350 3.42 10mph
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Old 05-13-2010, 04:39 PM   #11
Gregs71
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Re: engines and mileage

My 454 TBI with th400 in a 4x4 crew cab one ton is about 8 mpg
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Old 05-13-2010, 04:43 PM   #12
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Re: engines and mileage

Get a 6.2 diesel. My K10 got 24mpg hwy and would jerk your hat off your head and beat new tundras. Add a turbo and you win even more!
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Old 05-13-2010, 05:00 PM   #13
grinch4om
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Re: engines and mileage

wow...maybe I should just trade or sell this and get a late model or a diesel burban...or maybe not...I dunno...get the bike going again, then theres that scary road rash thing...
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Old 05-13-2010, 05:35 PM   #14
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Re: engines and mileage

I quit carring about MPG,now it's SMILES per mile!!
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Old 05-13-2010, 06:00 PM   #15
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Re: engines and mileage

Quote:
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I quit carring about MPG,now it's SMILES per mile!!
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Old 05-13-2010, 07:07 PM   #16
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Re: engines and mileage

Damn 13 with a BBC?

I am running a 350 and i get 9-12MPG in a '86 C10 longbed
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Old 05-13-2010, 07:20 PM   #17
Justin87
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Re: engines and mileage

My 2000 Sierra with the 5.3 and 3.73 gears averages 15 to 18 mpg.
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Old 05-13-2010, 07:21 PM   #18
flamingbig10
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Re: engines and mileage

355 th350 and 3.73 I get 5 but thats in town with stop and go traffic I get up to 11 on high way going 50 , but I will have a 6.0 and 4l80 pretty soon
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Old 05-13-2010, 07:24 PM   #19
bitchin85
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Re: engines and mileage

man id kill for a bigblockwith 8 let alone 13! i got a 350/350 with 3.42s and im happy if i get ten.. then again, i drive the **** out of my truck.. but if i were you, id for sure go diesel.. awesome mileage and they still got some nuts. and if you turbo it, itll be better all the way around
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Old 05-13-2010, 07:59 PM   #20
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Re: engines and mileage

see sig
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Old 05-13-2010, 08:40 PM   #21
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Re: engines and mileage

Dang. I'm going great then! I been getting 15-16mpg outa my 5000lbs 78 c20, 350/400. Maybe a lighter right foot would help....haha
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Old 05-13-2010, 10:14 PM   #22
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Re: engines and mileage

YA i have a 85 burb with 3/4 ton axles with 4:10 gears a 700r4 and get 7. With quadrjunk. I dream about 13 MPG....
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Old 05-13-2010, 10:43 PM   #23
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Re: engines and mileage

My '86 C10 longbed gets anywhere from 16-19mpg regularly and has seen 20mpg on a couple of long trips. Rebuilt stock 350 out of an '89 burb, rebuilt Q-jet and 700R4 with 3.42 gears. Not the fastest truck but quite pleased with the mileage.
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Old 05-13-2010, 11:15 PM   #24
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Re: engines and mileage

... mine is a '76 454 with all the head work, 750 carb & a turbo 400.. 12-14 mpg highway.
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Old 05-13-2010, 11:49 PM   #25
harnalien
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Re: engines and mileage

checked mine this evening, 12mpg. 350/700r4/3.73
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