400 rwhp and 20+ mpg?

[68shortwide]

What's the best way to go about 400 hp to the tires and still get 20-30 mpg? SBC or ls?

[C10_ustacould]

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.

[franken]

Look into vehicle weight and RWHP to see if the physics works.

[Heavymetl]

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!

[Grumpy old man]

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 .

[Nitis]

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

[MARKDTN]

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.

[52napco]

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

[tommys72]

Originally Posted by Grumpy old man

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 .

Well put!

[joey8383]

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.

[hamjet]

I still have one of those 150 MPG carbs if anyone's interested:>)

[67ChevyRedneck]

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.

[67swb72klb]

stick shift and a conservative right foot go a long way
20's can be a stretch with higher hp

[trac209]

Originally Posted by Nitis

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

^^^^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.

[trac209]

Originally Posted by 67ChevyRedneck

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.

.


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.

[chevy72blu]

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.

[1972RedNeck]

Originally Posted by joey8383

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.

I agree. If I drive it, it seems to drink fuel. Where people claim 14 - 16, I get about 12 with the same setup. When I am feeling cheap, I drive my Honda that gets 65 to 75 MPG - I even hit 86 one time.

[Fitz]

Originally Posted by franken

Look into vehicle weight and RWHP to see if the physics works.

Show us how that's done.

[flyingtim01]

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...

[68shortwide]

Originally Posted by flyingtim01

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...

Well I know nothing about diesels, though I could maybe go to school for it, I'm either going for engine building or metal fab but I could always go for diesel tech also, will probably put a dmax or Cummins in a lifted truck if I ever build one.

[1972BlueC20]

I have a 72 C20 with 350 and TH350 trans......I'm running an edeljunk carb.....I'm getting 10-11 mpg 95% city driving only with short driving distances.

I was a bit disappointed at first, but then I remember my 99 tahoe got about 12-16, and my 2010 GMC truck got 13-17 so it's really not bad for a 42 year old non-fuel injected brick rolling down the road...

I'm calling BS on anyone that is claiming they are getting more than 15 or 16 MPG with a stock configuration 67-72 truck with city driving....im not saying it's impossible but very hard to achieve.

[Grumpy old man]

Ah Guys ? the OP is 17 , Unemployed and doesn't have a truck yet . He came to the right place to learn how to build one eventually ...

[67chevy1series]

Originally Posted by 67ChevyRedneck

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.

Not only were you pulling the trailer and the weight of the truck but probably also had to fight the crappy are dynamics of the 67 as well!

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.

[68shortwide]

Originally Posted by Grumpy old man

Ah Guys ? the OP is 17 , Unemployed and doesn't have a truck yet . He came to the right place to learn how to build one eventually ...

I have the truck, just not to where I can work on it. So I'm gathering parts and ideas to bust ass on it when I get it to the shop

[Grumpy old man]

Originally Posted by 68shortwide

I have the truck, just not to where I can work on it. So I'm gathering parts and ideas to bust ass on it when I get it to the shop

Good ,this is the place to learn and get help ,Now lets see what truck your starting with .