25mpg 71 C10. Need Your Help!

[The Youngen]

Currently doing a restore on a 71 c10 lwb. It will be my daily driver and will stay around for a long time and id much rather drive this than a compact cars so please shoot out ideas for 25 mpg. It currently has a 350 with a edelbrock 1406 carb, weiand single plane intake, turbo 350, 3.73 rear, hei, stock ride height and tires. I was thinking about going to a 200 4r but figured id go all the way. Any engine/tranny combo will work. Manual is preferable. Diesel or gas. No A/C. No tree pulling or 1/4 miles. Just a cruiser for around town. Please help me out guys. Thanks!

[brad_man_72]

maybe a small diesel from a forklift or small car. i know for the price of the swap id buy a pos dd that gets good mielage and keep the truck fun.

[cam.man67]

merc diesel hooked up to anything. Check member cell's truck for info on the swap.

[biggestjohn]

Easy!! Have someone custom make a carbon fiber body, ( trucks are heavy ) have an aerodynamyicist reconfigure the body design ( these trucks are as aerodynamic as a brick ). Put a wee little 4 banger diesel in there, accelerate reeeal slow, and enjoy your new creation.

OK a little over the top there, sorry.

Your asking for 25mpg for cruising in town? The amount of money that you sink into trying to achieve this miracle will buy you a ton of gas. You will never see any savings.

[cam.man67]

See, I don't think it would be all that expensive to do. Might be even able to do it with a 6.2 Detroit diesel, T-5/TKO, and 3.07 rear.

[OJ1988]

25mpg on highway may be possible, maybe.
Overdrive tranny, go to a numericly lower rear gear like 2.73-3.08, lose the single plane and the edelbrock, go to a performer and tbi or a tpi set up.
Good exhaust, lighten truck as much as possible, lower it, tires as skinny as possible, 225-235, tune tune tune, etc...
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[woodwright]

Yeah I'll second the 6.2. My nephew had an 84 4wd with a 6.2and a turbo 350 and he got that kind mileage. With a 2WD drive truck and an overdrive tranny you could probably do better. And you can pick them up for cheap and they'll bolt in with minimal work
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[1972RedNeck]

Some 4BT cumminses have Chevy bellhousing patterns. Dad did a 4BT swap and got around 22 MPG at 80 mph.

[GCncsuHD]

Originally Posted by cam.man67

See, I don't think it would be all that expensive to do. Might be even able to do it with a 6.2 Detroit diesel, T-5/TKO, and 3.07 rear.

That seems like a feasible setup, and the 6.2 would actually probably like those ratios with the 4.03:1 1st and .76:1 5th gear in the s10 T5. I could see getting that mileage while having similar or better acceleration than a stock 6.2 with the 700r4's 3.06:1 1st.

I had always dreamed of a Cummins 3.9 4BT swap mated to a 700r4 or possibly a T5 as well, I have seen conversions "claiming" of 30mpg from those.

72redneck the 4BT itself does not have a Chevy bellhousing pattern, but the ones that came in breadtrucks commonly had adapter plates to mate them to the TH400.

[Hottrucks]

I was thinknig of the Isuzu deisal with the automatic behind it out of a box truck.......

cheap to buy with good parts available...also the size makes it an easy fit under the hood and tunnel

[GCncsuHD]

Originally Posted by Hottrucks

I was thinknig of the Isuzu deisal with the automatic behind it out of a box truck.......

cheap to buy with good parts available...also the size makes it an easy fit under the hood and tunnel

Yea Isuzu makes a 3.9L 4cyl diesel very similar to the Cummins 4BT that is pretty popular for conversions. 4BD1T I think?

[The Youngen]

Didn't think i would get this kinda of response in a couple of hours. I was looking at the cummins 4bt but i heard they are incredibly expensive. Ill look at the 6.2. Is it a good engine? Is it decently priced? Keep the ideas flowing guys, im loving it.

[GCncsuHD]

Originally Posted by The Youngen

Didn't think i would get this kinda of response in a couple of hours. I was looking at the cummins 4bt but i heard they are incredibly expensive. Ill look at the 6.2. Is it a good engine? Is it decently priced? Keep the ideas flowing guys, im loving it.

It is a good engine and yields great mileage, but it is gutless and does not hold up well to hotrodding, but driven normally it is pretty reliable.

[biggestjohn]

My B-I-L tried the 700r4 behind a 283 with 308 gears, only got 16mpg on highway. Changed to a 350, got 16mpg. The problem is that with such a low gear and overdrive, the engines couldn't get to the proper power band, they would lug at 60mph.

The package has to fit togather for the mileage increase.

You also have to look at the cost\benefit. Putting $3000+ into an effort to get a little bit of extra mileage just doesn't add up. And trying to get 25mpg cruising in town will never happen. In fact driving in town with a low gear ratio will actually have a reverse effect. The less mechanical torque available to start moving from a stop will increase gas useage.

Now if you have the money, and just want to experiment, then go for it. No better teacher than trying it for yourself.

[The Youngen]

Sorry, didnt mean 25 town, 25 highway since my driving is split so like 21 around town?

[Dano69c10]

4cyl diesel in your c-10 with a manual tranny.
You can always go electric.

[The Youngen]

I dont mean to sound rude but i did some research on the 6.2l. It looks like it is a decent engine and can be picked up cheaply. Thanks for the tip guys. Im going to discuss it over with the parents see if i get the green light.
I think the setup im going to shoot for is a 6.2l with a t5 and ill keep the 3.73's in the back. Would this work well? Would i have to beef up the t5? ideas please.

[todd99]

Fast ez-efi

[Hubscrub]

i can't believe nobody has said an Ls motor good power and mileage. Lots of people on here have swaped in newer V-8s like the 5.3 and 6.0.

[hugger6933]

If we were talking LS I would say look into the 4.8 They are a lot cheaper than the 5.3's more economical as well . In a truck [I am talking the truck they came in] 99-say 2006 with all being equal the 5.3 might get 18-20 and the same truck with a 4.8 might get 22-24. Now the 6.2 l diesel is a great powerplant I had one in a 89 c1500 that I would pull my car hauling trailer with it had about 250,000 when I quit using it much and sat for a couple of years then I could not get it to start again[pump problems] Now that truck would get about 20 mpg empty. I have a cousin that had a 83 swb silverado that had a 6.2 and he got 28 mpg on the hiway. Never could find out how. Now you can find the 6.2's on the c-list a lot of guys buy them surplus from hummers and you can get them with super low miles under 20,000 for a song. Your undertaking is not an easy one. You will spend a lot of money and still may be way short of your goal. Like I tell my dad when we are having a tough time about building the late model wrecks we rebuild" if it were easy everyone would do it" .Jim

[rob32472]

best I have got on avg with my ls is 20 if i keep the foot out of it

[crazy longhorn]

Originally Posted by rob32472

best I have got on avg with my ls is 20 if i keep the foot out of it

2nd that.....but I havent seen 20 yet(too many toes in the throttle) ? 2002 silverado/2wd extended, with a 4.8. The last tank on the hyway was 18mpg(cruising 75 mph, with the AC on). This truck is new to me, so I dont know if thats good or bad....but its sure better than the carburated stuff I was running crazyL

[Shaun1162]

I'd also have to say a 6.2 diesel....

The military CUCV 4x4 Blazers with a 6.2, TH400 and 3.08 gears get lower 20's for mileage. Like someone said before, with an automatic w/ overdrive or a 5 speed, you could pretty easily get 25 mpg I would think.

This might be wrong, but I thought I read somewhere that 6.2's can use 350 motor mounts (or at least with the CUCVs).

[The Youngen]

So a 6.2 without turbo. 700r4 and a 3.73 with stock tires would be a awesome setup?

[woodwright]

Sorry. Feeling a little snarky tonight.