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A Chevy V8 to a Six......

H

Henry G

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I have a near mint 87 Chevy 1/2 ton 4X4 pick up with 93k original miles and it runs great. Just too thirsty. It has I think 3.73 gears with a 700R4 trans and new 31" BF Goodrich All Terrains instead of the doughnut 235x15s. Been thinking about putting in an inline 6 with headwork, balanced and a little block decking just to bump up the compression a bit so I can run pump gas. I have had all the ones Chevy made over the years. Would a 292 with the gears and tires I got be a good choice? I had one with low 4.11 gears and got 13. My dads 67 had 3.08 or 3.40s and with a stick 3 speed got 21 at 55 or so back when it was the National Speed Limit. They are torquey for sure. I figure with the mods made to it, maybe an after market TBI or an Edelbrock set up it should run out really well and better somewhat on fuel. Make more room under the hood than an eight. Anyhow, Its a question I thought I would put out to you Chevy fans out there. BTW, I have a friend who has a 300 Ford (boo, hiss) inline six with 260 HP and about 450 ft. lbs of torque. Gets 18 when he drives it sanely. Has an AOD for a trans and an Edelbrock 4 bbl carb and headers. A screamer. I just want good power ( not a screamer) and better economy. He works for a speed shop here in Southern Oregon where I go to from time to time. Its called Ash Motorsports. Any, what do you think?:confused: Henry
 
If I was trying to get better mileage I think I would forget a gas inline 6, as the gains probably wouldn't be that substantial.

I'd go with a 6.2 diesel or Cummins 4BT diesel. 20+mpg out of the 6.2 and probably 25+ out of a 4BT.
 
We've got a 292 in the 3 ton grain truck. It certainly has lots of torque, but it definitely does not get good gas mileage...

A well built, sequentially fuel injected small block 350 can achieve 20+ mpg with overdrive, proper gearing, and sane driving, while still having the power to pull a trailer if required. Think about a multi-port conversion kit with a MegaSquirt ECM to provide the sequential injection, and coil pack ignition.
 
The costs of converting to ANYTHING from whats in there now would take a LOT of driving to recoup the costs. Figure even a 3MPG increase in a truck (that's quite a bit) and it still will take a fair bit of time.

Diesel is the quickest way to net much better mileage.
 
dyeager535 said:
The costs of converting to ANYTHING from whats in there now would take a LOT of driving to recoup the costs. Figure even a 3MPG increase in a truck (that's quite a bit) and it still will take a fair bit of time.

Diesel is the quickest way to net much better mileage.
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X2, swapping to anything but a diesel to gain mileage is :screwy:
 
Diesel! A 6BT for power and better mileage. A 4BT for a lot better mileage. 3.73 gearing and a 700r4 I'd say you'll get 30+ and quite possibly 35+ for mileage. Definately would need another TC though.
 
buy a beater car and use it. Thats the easy way to get better gas mileage. I6 or V8 dont matter too much, Your still moving a heavy truck and thats what kills gas milage. That and its shaped like a brick.
 
merace19 said:
I6 or V8 dont matter too much, Your still moving a heavy truck and thats what kills gas milage.
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Exactly, which is why diesel really is the only reasonable option for a mileage swap, as it's the only type of engine that can break through that wall that a gas engine can't of "it still weighs X amount and is a big truck and will still take X amount of gas regardless of CI. Since diesels are so efficient they can push through that and make a big heavy truck get the mileage of a small mini pickup with a 4 banger!
 
If I could do it all over again, I would have kept the old '81 SWB I had years ago. It had 3.73 gears and a 465 tranny. The motor was a good running 250 inline 6. I got 18 mpg with that setup. I regret selling that truck. That was probably the best combination in a truck like that for fuel economy.
 
A 292??..NOOOooooooo!!

I've had a few 292 motors,and friends have too--none got more than 12-15 mpg,even in perfect tune,with a rebuilt carb,etc..they are great for torque,but they are more thirsty than most V8's are!..I've had 454's that did better on gas than my 292's did,and they could smoke the tires in all 3 gears..

I'd agree a diesel is the only way to get much more than 16 mpg in a full sized GM truck..the areodynamics are against you,a square wind plow will never be fuel efficient,no matter what engine is pushing it down the road..the diesels are hard to beat for fuel economy..but you wont get 20+ mpg either,(except maybe from a 4BT Cummins)--anyone who says you will get better than that, is smoking something illegal..:rolleyes: ...

Not to say a fuel injected 292 with a cam and headers wouldn't be cool,and probably a torque monster!..:laugh: --but for a street driven daily driver,not the hot setup at all,for getting good gas mileage...:crazy:
 
Whats the hard on about the 292? All I've heard is its good for torque, thats it. I'd stick a good built 250 in there any day and save money on gas with the economy that motor will put out.
 
Isn't your 87 TBI Fuel Injected? 31's, 3.73's, a 700R4, and a good running 350 should be capable of 12-15 in town and up to 20 on the highway. That's a great combo. Put that 6 cyl money toward headers/exhaust and a good tune-up, or buy an econobox. You could build a TBI friendly 350 with vortec heads and a roller cam for what you'll spend on building a 6 cyl.
 
diesel4me said:
.the diesels are hard to beat for fuel economy..but you wont get 20+ mpg either,(except maybe from a 4BT Cummins)--anyone who says you will get better than that, is smoking something illegal..:rolleyes: ...
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How do you figure? Most of the 6.2 K5 guys claim 20+ on the highway with a 700R4. A 4BT in a 1/2t K5 could probably even touch 30mpg under the right circumstances. Heck, I get 22mpg with my Ram Cummins that has a 355HP ISB Cummins, weighs 7K, and is a 4x4 long bed quad cab.
 
Well CK5, I got the answers I need. I think the I6 is a great design but a 4BT may just be the answer. Not too sure where to get one as I want to keep this rig. Just down thje street from where I live is Tucker Snow Cat Company. They put them in their Snow Cats and I heard they work out REAL well. Perhaps they can tell me where to get one shoiuld I go that route which is a real possibility. Too nice and hard to find not in a beater condition. I have heard of one person somewhere here in the valley of southern Oregon, (Medford area) that put a 6BT with the newer Trans and TC in a 4X4 Suburban and absolutely loves it. Comfort, power and economy. Thanks for all your help. Its really appreciated. H.
 
hmmm interesting...

im getting about 11mpg with my non od truck.. it is not a dd so that is ok..

I am going to buy a crew cab and the donor is a 6.2l diesel and runs.. hmm maybe I should swap out and go diesel..... however better gas mileage but not better performance... from what im hearing yes more torque and better gas mileage.. plus fuel injected (diesel)...... however low hp...

I think the 6.2l non turbo was 135hp 295lb ft torque and turbo'd was 155hp and not sure on the torque side.... with that it doesnt seem right as what people say is you cant get out of your own way.. but hey you can pull a barn with you :haha:
 
I wanna know who honeslty get 20 mpg with one of these truck (gas) no matter what the setup or the driver:rolleyes: Not gonna happen.

With new trucks your lucky to be in the mid to upper teens...
 
As stated above, I got 18 mpg with an '81 SWB, 250, 465, 208, 3.73's on 33" tires. Honest truth, thats my story and I'm sticking with it.
 
I can understand 18 from a easy driven truck and flat kansas but no way anyones getting over 20 with a v8 and tbi (hell multiport in one of these trucks)

thatK30guy said:
As stated above, I got 18 mpg with an '81 SWB, 250, 465, 208, 3.73's on 33" tires. Honest truth, thats my story and I'm sticking with it.
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79k20350 said:
I can understand 18 from a easy driven truck and flat kansas but no way anyones getting over 20 with a v8 and tbi (hell multiport in one of these trucks)
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my uncle in law has a 05 or 06 gmc fullsize 4wd.... stock though.. he said he can pull 18 in upstate ny..... he is very light footed.. he leaves the heavy foot for the 66 vette convertible with a 427 for that task.... or the 02 50th anniversary vette for corner fun... so pickup is all easy going... :haha:


oh yeah I thought about going diesel to make bio diesel.. thus making gas like $.75 a gallon...
 
my dd '94 c1500 w/4.3L tbi v6 gets around 17 in the horrible stop-n-go traffic i have to put up with every day. when i get it on the open road and cruise at 80+, mpg rises to about 23. my best ever is 28mpg on a long roadtrip.

my 82 k5's original engine got 8-15mpg, and i think the reman is getting 12-15 or so.

needless to say, i miss my '87 honda, sometimes. would be nice for the commute.
 
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