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#1 |
Registered User
Join Date: Jul 2014
Location: Missouri
Posts: 1,427
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400 rwhp and 20+ mpg?
What's the best way to go about 400 hp to the tires and still get 20-30 mpg? SBC or ls?
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Jack Personal Fleet: Family Fleet: 1955.5 Panel 1959 Apache 1968 ShortWide 1969 ShortStep |
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#2 |
A day late and $1 short...
Join Date: Dec 2008
Location: Northwest FL
Posts: 3,870
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Re: 400 rwhp and 20+ mpg?
LS will get you close to that, although I'm not convinced it is possible to get 20+ mpg. These trucks are bricks moving through the wind. My '68 stepside with 5.3/4L60E achieved about 15-18 depending on driving conditions.
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Buck Instagram: C10_ustacould 1963 SWB Fleet Side 528 Desert Beige Milly 1967 SWB Step Side 506 Medium Blue The Old Girl 1968 SWB Fleet Side 503 Light Green Ellie SOLD 1965 SWB Fleet Side 507 Light Blue Prescription Strength SOLD 1971 SWB Fleet Side 521 White Shiro SOLD 1968 SWB Step Side 503 Light Green My Old Farm Truck SOLD |
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#3 |
Registered User
Join Date: Jun 2013
Location: Somewhere
Posts: 3,073
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Re: 400 rwhp and 20+ mpg?
Look into vehicle weight and RWHP to see if the physics works.
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#4 |
Registered User
Join Date: Feb 2012
Location: Southern Ohio
Posts: 292
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Re: 400 rwhp and 20+ mpg?
My 347" LS dynoed 445rwhp and has knocked down 25mpg on the highway. But it's in a Camaro, which is considerably lighter and more aerodynamic.
The best path for 400rwhp and 20 mpg in a truck is LS and "hypermiler" driving techniques! |
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#5 |
Senior Member
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Location: Gods country East,Tn
Posts: 8,545
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Re: 400 rwhp and 20+ mpg?
I understand everyone wants better gas mileage and HP , I want a super model who loves to cook and clean house and is happy to wear a potato sack and never spends any of my money . Ain't gonna happen ! I've seen guys try to do it and spend $1,000's on mods to be fuel efficient when they could have just paid the price of the fuel and buy a beater mini truck to get to work every day instead of driving their COOL truck and hating to feed it .
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#6 | |
Registered User
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Location: springfield mo
Posts: 3,075
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Re: 400 rwhp and 20+ mpg?
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United States Marine Corps 2000-2011 Iraq and Afghanistan veteran Just living life now and enjoying it and my wife, daughter and son ![]() |
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#7 |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 400 rwhp and 20+ mpg?
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#8 |
Registered User
Join Date: Apr 2014
Location: NOR-CAL
Posts: 1,134
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Re: 400 rwhp and 20+ mpg?
Well you won't get the horsepower but if mileage is what you want my dream is a swb truck with a cummins 4bt
With the right gearing and a manual trans 25+ shouldn't be an issue |
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#9 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,148
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Re: 400 rwhp and 20+ mpg?
I would look at a 4.8 LS with a turbo. Couple it with a 6-speed auto. You could get there with the right gear out back-and have a screamer when you wanted it.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#10 |
Registered User
Join Date: Dec 2011
Location: winnipeg
Posts: 1,107
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Re: 400 rwhp and 20+ mpg?
^^^^this is about the best advice you'll get. If you have 450 plus hp it's doubtful the truck will get that cuz you'll always be on it lol.
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#11 |
Registered User
Join Date: Jun 2014
Location: upstate sc
Posts: 2,095
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Re: 400 rwhp and 20+ mpg?
My Datsun 280z makes 428 RWHP LS6 w T56 manual and will knock down 27-28 mpg all day but weighs 2640lbs. My 1971 RS Camaro will get 27 MPG if you act right with and it makes 606 RWHP with a magnacharged LS6 with 5 speed manual both have 3.70 gears so even in a truck 20+ would be very realistic but only LS powered and FUEL INJECTED
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#12 |
Registered User
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Location: Okmulgee, OK
Posts: 205
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Re: 400 rwhp and 20+ mpg?
I would love to know how everybody achieves these high mpg's! I have owned a FEW 5.3 trucks and a 4.8 truck and always avg 13-14 mpg. Maybe 16-17 on all highway. Maybe I drive faster..
All the cummins guys claim 20+ mpg and I have had 2 24 valve 5.9's and a 6.7 cummins and even though the display shows 17mpg, on paper it always came out to 12-13 mpg. OP, Big power+fuel efficient= LS. No doubt the LS based engines will beat the sbc in every aspect. |
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#13 | |
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Join Date: Jan 2011
Location: Townsend MT
Posts: 1,725
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Re: 400 rwhp and 20+ mpg?
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#14 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 400 rwhp and 20+ mpg?
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#15 |
Registered User
Join Date: Nov 2010
Location: Grand Terrace, Ca.
Posts: 1,607
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Re: 400 rwhp and 20+ mpg?
You can get good fuel mileage and be able to make big horsepower, you won't be able to get good fuel mileage while making big horsepower.
Small(ish) cu.in. well prepared motor + turbocharger(s) + EFI + reasonable gear ratios can get you the ability to make big horsepower and get good fuel mileage. |
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#16 | |
Registered User
Join Date: Jul 2013
Location: Winnsboro Texas
Posts: 367
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Re: 400 rwhp and 20+ mpg?
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The bitterness of poor quality lingers long after the sweetness of a low price is forgotten. |
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#17 |
RAT1968 '68 Cab/'71 Parts
Join Date: Feb 2002
Location: Coarsegold, CA
Posts: 2,375
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Re: 400 rwhp and 20+ mpg?
I was told one time, "...It's like trying to push a brick through plastic wrap".
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M17 Coarsegold, CA RAT's shiny now. But always a rat. |
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#18 |
Registered User
Join Date: Sep 2006
Location: Riverton KS
Posts: 832
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Re: 400 rwhp and 20+ mpg?
I think this thread might be the ultimate pi**ing match
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#19 |
Registered User
Join Date: Apr 2013
Location: South Westerlo, New York
Posts: 1,325
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Re: 400 rwhp and 20+ mpg?
I still have one of those 150 MPG carbs if anyone's interested:>)
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#20 |
Hittin E-Z Street on Mud Tires
![]() Join Date: Nov 2004
Location: Greenville, SC
Posts: 23,090
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Re: 400 rwhp and 20+ mpg?
20-30 mpg?
![]() Modern midsize trucks can't even achieve close to that. Even with a fuel injected LS and OD, expect 12-14 around town and 17-20 highway depending on your driving style/habit (and rear end gear!). Anything over 60mph on the highway and you start to lose mpg with these trucks (huge bricks). The older Cummins with a manual can absolutely get mid 20's. My uncle has owned a 94 Ram reg cab longbed with a cummins for probably 15 years now. He hauled my 67 from NY to SC for me (rode with him) and hand calcs (GPS verified) showed 17 MPG with a 2500 lb trailer and 4K pound truck. He regularly gets low to mid 20's unloaded on the highway. I have read the newer ones are way up on power, but emissions (and the sheer size and weight of the newer trucks!) have killed economy.
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Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride ![]() American Born, Country by the Grace of God ![]() 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! |
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#21 | |
Registered User
Join Date: Dec 2011
Location: winnipeg
Posts: 1,107
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Re: 400 rwhp and 20+ mpg?
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This is also very true. My grocery getter mazda 3 doesn't get any better then 30 mpg highway. I doubt any full size truck comes close to 30 mpg downhill. Though I see the big three try to claim otherwise. Trying to get 30 mpg in these trucks when new factory trucks can't is like saying we know more then the engineers at gm,ford etc. We all would like better mpg and there's ways to improve most times but being realistic is also key. |
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#22 |
Registered User
Join Date: Apr 2004
Location: Las Vegas, NV
Posts: 2,188
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Re: 400 rwhp and 20+ mpg?
Bone stock LS1/4l60E with 3.73 and a 29" tire. I've never done better than 22.5 MPG highway and that was driving like a grandma, probably with a tail wind
![]() Truck weighs right at 4000 lbs. 400hp and 20mpg can probably be done, but it wont be easy and likely wont be under "normal" driving. I'd still go LS if I were you - just keep your expectations reasonable.
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RIP EastSideLowLife '72 C20 SWB convert. 5 lug, LS1/4l60e |
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#23 | |
Registered User
Join Date: Mar 2010
Location: a t w a t e r cali 95301
Posts: 10,713
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Re: 400 rwhp and 20+ mpg?
Quote:
When it comes to these trucks I feel as long as when I tromp down on the gas that thing feels like it just lost 700 pounds and starts to fly down the road, I would live with 15 in the city or over. There's always a price to pay in our case owning a c10 means you'll never know what good gas mileage feels like... Or you can find out what semi good gas mileage is but you'll have to spend a couple thousand for an LS. |
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#24 |
Registered User
Join Date: Dec 2010
Location: livingston co.mi
Posts: 2,453
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Re: 400 rwhp and 20+ mpg?
stick shift and a conservative right foot go a long way
20's can be a stretch with higher hp
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#25 |
Registered User
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Location: Clinton, CT
Posts: 101
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Re: 400 rwhp and 20+ mpg?
My Duramax gets about 22mpg on the highway empty, and with a tune you'd probably be able to get 400hp to the rear wheels...
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