Best engine/trans set up for GREAT gas mileage

[jayssunm]

I have had my C-10 SWB truck for nearly 10 yrs put in a 350 a while ago but now consider finishing her up.

Here are my questions:

1) If you were to build a project you wanted to sell what eng/trans setup would you put in?

2) If you wanted a super clean inexpensive daily driver (read GREAT gas mileage) what would you install?


I have read many many post to what people should get based on a engine/trans setup. I am more curious about what people actually do get for gas mileage. (yes have considered going bacl to straight 6 if someone can vouch for around 20+ mpg)

Thanks for your replies.

[Shyguy]

Besides the engine/trans combo you will also have to consider the rearend gearing and tire size.

A mildly built 350 with a 700R4 and the right gearing and tire size should produce pretty good mileage.

I am running a stock 350 with a granny 4 speed, 3.73 gears and 31's and get between 13-15 mpg in my '71

Danny

[Frizzle Fry]

An AOD behind a modern V6 would probably do pretty well.

[samwise68]

No idea on what would sell - depends on the buyer.

But i'm pulling a consistent 16-17 mpg with my GMC, stock (tired..about 95K on the clock), with a 2 bbl and headers, HEI, 3 on the tree, and 3.07 gears, with 235/75 tires.

I turn about 2 grand on the highway at 55-60 mph, which helps greatly for milage.

But, thats just what I have experience with, so take it with a grain of salt.

-Sam.

[ChevLoRay]

Originally Posted by Frizzle Fry

An AOD behind a modern V6 would probably do pretty well.

I'm running a 4.3 and the stock AOD in my '96, getting around 17 in town. Haven't filled it up since I got back from my little road trip, but I expect to get around 19.

But, I sure do miss the V-8 that is in my '69. It ain't no daily driver, so I reckon it don't matter none.

[SactoJim]

I'd say a late model Vortec 4.3 with Overdrive tranny.....no powerhouse but at 190 hp...it'll get out of it's own way.

If ya gotta have a V8, go with a 4.8 LS motor out of a truck.

[steelhorse]

To hell with exxon put a 572 with a blower in it.Oh and buy a civic to drive daily

[PanelDeland]

A lot of members claim better milage with the 307's.If I were strickly looking for milage I would have to determine whether I would do more highway or city driving.If Hiway I would probably go with the 307,a 200R4,and maybe a 3:42 or 3:55.For the city stuff I would probably do the same but use a 3:73 rear.A two barrell,and headers with a 2 in or so exhaust and maybe an RV cam.For hiway I would also cover the bed either a lightweight cap or a tonnue.

[Jim_PA]

Efficiency is more important than engine size. A v6 moving around a 4400+lb truck isn't going to necessarily give you better gas mileage.

If you can get 15-17 driving conservativelvy (which I can...) I'd consider it a win.

I think the ultimate in ecomoy would be a cummins 4BT. I also think you can achieve decent mileage with a well thought out 350 with some 3.42's and a manual OD trans.

[67_C-30]

I believe a LS series 4.8L with a 4L60E or better yet a 5 speed would do real good. They produce close to 300HP and put good numbers in newer (heavier) trucks. I have one in my 2000 Z71 and I have got as good as 21 on the highway with 33" tires. My truck weighs 4890# unloaded, and I believe that if the 4.8L were in a SWB truck weighing around 4000# it would do very well. I wish I knew of someone had actually done this swap.

[IvelDesigns]

my 2bbl 283 with a turbo 400 and 2.73 gears seems to do me pretty well. i'm not sure on the exact mileage, but i made it about 200 miles on about 14 gal of gas. average speed was around 70mph a couple weeks ago.

[hgs_notes]

My wifes 2003 Yukon XL Denali has the 6.0l and AWD and will get 18-20 on the hwy if your not driving into the wind. 17-18 normally on the hwy.

I imagine it would do better if installed in a much lighter, 2wd pickup. I know I'd love it in mine. That thing will fly, there goes the gas milage.

[Gray Ghost]

I am going to add TPI to my 300 hp 350 and then add in a 700R4 built for towing later on this summer. I hope to get into the high teens or low 20's with mileage.

Sure would like to ride with one of you guys claiming 15+ mpg...especially the one who has the 3.73's. Mine gets 12 on a good day carrying about 450 extra pounds of tools without any AC and a 3.07 in back. You all must be hypermiling or something.

[LONGHAIR]

i'm not sure on the exact mileage, but i made it about 200 miles on about 14 gal of gas.

That works out to about 14MPG

That TH400 is killing you. It takes more power to turn them than many other transmissions. 2.73 gears aren't doing you any favors in the city either. A 283 is no torque monster, so you are pulling pretty hard on it from a standing start.

[caminokid]

Originally Posted by steelhorse

To hell with exxon put a 572 with a blower in it.Oh and buy a civic to drive daily

Not just any 572....the 572/720 motor! Pass everything but a gas pump!

Do your self a favor...Get the Edelbrock performer package for your 350. Cam, Intake and carb. If you can afford it...get the Performer heads too. With everything matched you will get better gas millage. With just the intake carb and cam....I got 311 miles on 3/4 of a tank of gas in a 77 El Camino SS.

[Sinisterspeed]

Well me personally the newer engine is not doing me any favors. I have a 01 GMC with 6.0L and 4L60E, 4.10 and 35" tires it gets 7.4 with my trailer and maybe 11 without. It did get 13 hwy when it had 33's. The 72 GMC I took apart had 35" tires 4.10 gears, TH350 and 383 this truck believe it or not got 16 mpg on the hwy. Never pulled with it so I dont know what it would do there. Both of these trucks are 4wd and a bit heavier then a 2wd swb would be. Not that any of this really helps but just though I would add my .02

[67shortie]

I wonder if one can fab a supercharged 3.8 out of a late model GM car in one of our engine bays?

My SSEi has one,good power and almost 30 on the freeway, and it's no lightweight weighing in at 3700 lbs.

The difficulty might be trans and motor mounts but I am sure it could be done.

That combo with a TH7004r might get mid 20's and one can boost power levels with pulleys and exhaust mods....

[1971ChevyTruck]

What about a 350 with a 700r4 trans and 3:73 gears?? Stock everything except for headers.

[subalternnavert]

A well built 305 V-6

[19723DR]

I have a '93 extra cab silverado with a 4.3 and a 5 speed and I get 17-18 mpg around town and 25-26 highway. It still has plenty of power and is really fun to drive. I'm going to be building a '71 short bed with a 4.3 vortec with an AOD we'll see what kind of mileage I get out of it. The engine came from a '93 Jimmy I used to own and it kicked butt in that thing with tons of power and very good gas mileage.

[rustSpot]

I would agree on the 4.8. Currently daily driving a 2007 crew cab getting around 21 on the hwy and 17-18 around town. Amazing mileage for a large truck. Entertaining the thought of a 4.8 in my 67.

[hgs_notes]

I was told by a mechanic friend that a well tuned rochester 4 barrel carb can help milage over a holley because of the small primaries and holleys, from my own experience always run rich, especially down low. They make good power and poor mileage.

[67ChevyRedneck]

EFI 5.7L or 99+5.3L (all are EFI) backed by a 700R4 or 4L60E with a 3.42 rear end.

The 700R4 is by far the simplest AOD tranny to use. There are many "cheap" kits to make them work with 350's. The 4L60 (modern 700R4) is completely computer controlled. A 5.3/4L60 combo with all the wiring would work well (with aftermarket tunes) but can get expensive quickly.

[Deuce]

TPI 305 and a 5 speed.
Torquey small motor with FI and a 5 speed. Should work good in a heavy truck.

[SCOTI]

Originally Posted by hgs_notes

I was told by a mechanic friend that a well tuned rochester 4 barrel carb can help milage over a holley because of the small primaries and holleys, from my own experience always run rich, especially down low. They make good power and poor mileage.

Very true if comparing a Q-jet to the typical vac secondary Holley (3310's).

But, Holley makes a nice little vac secondary Q-ject 'replacement' carb specifically for GM 350-455's. It's 650cfm, has the smaller primaries & electric choke. That would be a better comparison. I used one in my old camino w/a 355/350, 218/228 hyd cam, & 3.08's & got 13-14mpgs around town.