57 GMC - drive train for good mileage

Just throwing this out for opinion. I am looking to buy a 1957 GMC pick up. Hopefully a fleetside. If anyone has one for sale let me know. I want to build it for a daily driver. I am looking for opinions on what would be the best engine, transmission and rear end for the best possible gas mileage and decent power. I would like to run a manual trans (5 speed) and make it a 4x4. Not necessarily lifted or for anything, just for weather reasons and practicality. I have front and rear axles from a late 80's Chevy 4x4 Blazer, a NP205 transfer case and springs, perches, brake booster and master cylinder. Thanks in advance for the input.

 

Well with a 4X4 you ain't gona win any milage contests. Untill I saw the manual trans and 4X4 I would have said a 283-305 with a 200R4 with a Quadrajet. Resist the urge for big rubber which don't help milage. But a q-jet on a 283 with 9 -1 comp and a a RV type cam should not be to bad.And you for sure want lock out hubs as full time stuff kills milage.

 

My Dad has a 57 Jimmy and regrets everyday that he took out the stock 347 V8. He replaced it with a 383 stroker crate from Chevrolet high performance parts and now he can even afford to drive it....he was getting a good 15 miles on the 347 and i say that would be the way to go.

 

Serious options to consider are:
The buick 350. Lightest of ALL the small blocks, and a serious torque monster. Torque gets you moving without using too much pedal. These came stock in some Jeeps back in the early 70's, and they are coveted by the classic jeep enthusiasts for being powerfull and efficent.

6.2 GM/Chevy diesel. I used to have a 1500 with this engine, 4wd, and it got a solid 22 mpg. It uses the same motor mounts and bellhousing as the sbc. Power [in it's stock form] is comperable to a 305 gas sbc. you wont win many drag races, but you can pull a house with this engine! As a bonus, make your own bio-diesel for $1.50 a gallon, or convert it to run on straight veggie oil!

Inline 6 might be a reasonable option. Again, you wont win any drag races, but the efficency is a fair trade off. Plus, it's HAMB friendly.

Just my opinion, your mileage may vary...

 

In that truck? An Isuzu 4BT diesel. More power than the 6.2 and should pull you 25 MPG with no trouble, maybe even higher. The 6.2 you may be pushing it to get 25, some claim to get that in the later blocky 80's Chevy trucks but usually only a 1/2 ton 2wd. The 4BT is what they use in delivery vans like UPS trucks and can be adapted to both Chevy and Ford bellhousing patterns.

Second choice would be any of the stock Pontiac choices - the 336 (GMC only), 347, or 389 - with a 4-speed or 5-speed manual trans. You should be able to get between 15 and 20 with a light foot - going 2WD would help, again. With these motors the torque is there to run a good highway gear and go fast and not necessarily need an overdrive.

Third choice would be a newer GM diesel, either the 6.2 or the Olds 5.7 diesel. On the 5.7, if you rebuild it use new head gaskets and head BOLTS and it should be relatively trouble free. Even if you don't rebuild it, if you don't know the mechanical history, change the head bolts for new ones. That will let you run a 200R4, but it's more inclined for a 2wd setup. The 6.2 could come stock in a Blazer and you'd run a 700R4 with it. Manuals exist but the flywheel is tough to source. They have their own set of bugs, but with care can run 500,000 miles. It also doesn't like to run over 3000 RPM and most are goverend to 3600 so you don't make them fly apart - gear it to run down the highway at your cruising speed in overdrive, at about 2000 RPM for the best economy.

Now, you live in southern California. Just what does it do there that you're ever going to need 4x4 for except occasional off-road driving? I live in New York, one of the snowiest parts, and I get around fine year round with 2WD, including some off-road driving. Having a locker rearend is key, I've even gotten myself out of some pretty serious mud and across glare ice with just snow tires on the back, not even chains or studs. But the second Suburban I bought has an open rear and is just about useless in the mud.

The lower to the ground and the less friction to the road surface, the better the MPG - tall skinny tires help. But 4x4 and high MPG are pretty much a contradiction in terms, unless you build a diesel S10 (you could stick an AD Chevy body on that one I suppose).

 

I'd try one of those new stright sixes, out of the Bravado. 300 HP, all aluminum block, fuel inj. Keep the OD trans, and rear, as well, probably get close to 30 MPG in your old truck....not traditional though!

 

Mileage and 4x4 don't go together. You'll have higher rolling resistance, weight, driveline loss, and even less aero than the stocker. I'd expect 10-15 out of any fullsize V8 4x4. Having owned a handful of square body chevy 4x4s with similar drivelines, you're gonna discover a weird mileage quirk. It'll work the engine so hard there's not much mileage penalty for engine size. The mileage difference between a 6 and a 350 and a 454 is only 1-2 mpg per step. So if a weak-suck engine only nets you 3-4 mpg over a big block, makes the small engine a lot less desireable. good luck

 

Thanks for everyone for the replies. In response to rustynewyorkers reply - I do agree. It's not like I live in Siberia but I do have to drive in the snow up some hills and I want to aleviate my need for chains. I know 4x4 and mileage don't mix but that's where I'm at. I would love a diesel but the price of fuel here is nuts so it would really have to impress me. I wouldn't mind an inline six but what could I do as far as a transfer case and tranny combo.? Also I want to be able to haul stuff so I am wondering if it is too gutless. Thanks again for all the advice and keep it coming. I am still looking for a truck too so if anyone is out there with a good candidate let me know.

 

Hands down one of these, you can't beat em for low cost, torque and mileage........

4.6 3- valve Explorer engine available from Kar Kraft new complete for $1995.00

 

I'm getting 17 mpg out of a stock suspension '57 Chevy short bed with a 350 4 barrel with no vacuum advance, a T-5, 30 inch tall commando tires, and a 3.08 peg leg 12 bolt.

P.S.... The fleetside bed didn't start until '58.

 

Chevy sixes will bolt right up to transmissions and tfer cases out of V8 equipped trucks. And there's guys that have pulled 2 ton trailers across the country with em, but you couldn't pay me to put one in a 4x4 with all the parasitic power loss it'd endure.

You might just wanna look for a squarebody chevy parts truck. They're trading for dirt money around here, you can buy a complete rusted truck for $250 every day of the week. Me and my buddies pillage for what we need, then the scrapyard returns $150 of the purchase price. Right now are the golden days of cheap, durable, 4x4 driveline components. Good luck

 

Find a rusty S10 4X4 with 4.3 and swap your body onto the chassis. Great torsion bar front end, front discs, fuel injection, tough little trucks. If you find an extended cab the frame will be long enough to shorten to the right size. Always better to shorten a frame than lengthen it, but the S10 is made to be varying lengths, there's a straight section that the factory cuts and welds to fit all wheelbases.