mpg guess on possible new setup for me

[trkklr77]

I RRRREEEEEEEEEEAAAAALLLLLLLLLLLYYYYYYYYYY dont want to sell my short 71. BUT i spun a bearing in the bbc so it has to come out to get fixed. i also am looking at a new job where i will need to be driving 100m minimum daily. there in lies the delema, i can sell my roller short fleet for a nice $$$ and get a toy or newer chevy [89-98] for the gas.

it has been suggested by a few freinds that if i
3.07
700r4
taller tire
the truck i should get around 15mpg, does this sound feasable or should i be coughing up smoke rings?

the reality is the difference of money, $2500 inbound or $1000 from my pocket, i have found quite a few possible new rides but i KNOW i will hate myself for ever if i sell the shorty.

i want to hear what yall think.

[GREASEMONKEY72]

the combination of all would probly get you around 15mpg but just one or 2 of those i dont think will get you up that high but will get you higher than you are now but its also on how you drive to, if you leave a bit sooner and drive 55mph instead of say 75mph youll get better mpg there and also if you leave the light slower and build up to speed instead of getting up to speed as fast as possible youll save gas that way to but in the end its all up to you in what would be your best bet, and if you dont have any of those things yet itll most likely cost more than 2500 that you would get for the truck to put in a new trans, gears and tires

sorry for rambling

[mnunn454]

Since you're in love with the truck (and it appears the BBC power too) I'd leave the truck as is, and spend a little on a more economical daily driver with a V6 and an overdrive tranny.

My $2500 95 Olds Eighty Eight DD gets 25+ MPG. The difference in MPG between a DD like this and your 15MPG truck (after the SBC/OD driveline conversion) will quickly pay for itself given today's escalating fuel prices when you're driving 100 miles a day.

If I do the math, a 10MPG improvement generates $30 or more a day in savings at 100 miles a day. That's $600 or more a month in fuel savings that could be otherwise put to better use (like fixing the BBC?)

Just a thought.

[byrd]

I don't see whay you would have any trouble getting to 15 mpg. I have a 350/350 th and 3:73 and I get a steady 13 mpg all around highway and in town. I would like to see what the taller gear would do intown when not using the OD. Although with the taller gears and the torque needed to make these trucks move you might have to travel at 75 mph to get into the power range of the motor.

My project's drivetrain was built for daily driving. I have a mostly stock(small cam upgrade) 250HP 350, with a 200r4, and 3:07 rear. I will only use OD on the highway @ or above 65 MPH. With a 28" tall tire it should be right around 1750-1850 RPM's in OD @ 75 mph. Now the cam is set to make it's power from 1600-2600 rpms, so it should be optimum for fuel milage given the engine is making enough torque @ 1800 not to bog down from the wind resistance @ 75 mph. If the combo doesn't work for me I will change the rear to a 3:42. I wish I had some real life experience with this combo to give you better feedback, but imo it should work out great.

[mrein3]

Originally Posted by byrd

snip...

My project's drivetrain was built for daily driving. I have a mostly stock(small cam upgrade) 250HP 350, with a 200r4, and 3:07 rear. I will only use OD on the highway @ or above 65 MPH. With a 28" tall tire it should be right around 1750-1850 RPM's in OD @ 75 mph. Now the cam is set to make it's power from 1600-2600 rpms, so it should be optimum for fuel milage given the engine is making enough torque @ 1800 not to bog down from the wind resistance @ 75 mph. If the combo doesn't work for me I will change the rear to a 3:42. I wish I had some real life experience with this combo to give you better feedback, but imo it should work out great.

byrd touches on some important things here. MANY people put a .7:1 overdrive tranny (700r4, 2004r, many manuals) in only to find out that with their 307 rear end they got LOWER mileage.

Here is what I'd do:
Figure out what your commuting speed is MOST of the time. Do like byrd and figure out what a 28" tall tire and a .7:1 ratio will be doing with a 307 rear end at that speed. You just may be better off with a 373 rear or 411 or 342 at that speed.

Once you got that all figured out I'd do what mnunn454 said. Except I wouldn't stop at 25mpg for your commuter. I've been getting 34-38 miles per gallon with my 1994 Ford Escort since I bought it new in January of 1994. It has worked with little maintenance for 272,xxx miles, all the time racking up mpg numbers over 30. Long commutes in these little cars is what they were made for.

Now do some math. Since January of 1994, my commute being 76 +/- miles per day, I've consumed 8000 gallons of gas. A very well set up truck, getting 15 mpg, will consume 18,133.33 gallons of gas. If you pay $3.00/gallon for that amount of gas over 13 years you'll spend $54,400 in the 15 mpg truck and $24,000 in the 34 mpg car. You're saving $30,400 over 13 years or $2338.46/year. Now if you're doing 100 miles per day or 25% more, you have to scale those numbers up. $68,000 in the truck, $30,000 in the car. What can you buy for the $38,000 you'd save in the commuter.

G6, Focus, Cobolt, pick your favorite, get one with a 5-speed, drive the crap out of it. (And don't let the secret out to the Toyota and Honda buyers that you can get an American made, well built, low maintenance car for $10,000 brand spanking new)

[byrd]

G6, Focus, Cobolt, pick your favorite, get one with a 5-speed, drive the crap out of it. (And don't let the secret out to the Toyota and Honda buyers that you can get an American made, well built, low maintenance car for $10,000 brand spanking new)

Very well stated!!!!!! and excellent comparision. My DD(98 cirrus)gets 21 all the time so my cost comparision will be a lot closer in actual cost, but the car is hand me down from the wife, she gets all the new ones first so not cost output for it and has been paid off for 6 years. A great car, a few small issues all fixed under warranty, but it has 140K and still runs just as good as the day we bough it, and haven't put a dime in it in almost 4 years(except normal maint)
We have a 05 cobalt ls got it for $13K brand new. 2 yrs and 21K not a lick of trouble. It averages 28 in town and my wife almost never takes the highway to work,it is suppossed to get 32 on the highway. We have taken it to Cinn,Oh about 2 hrs from here and it averaged 31 with 3 people and the a/c on full blast.

[Boog]

TK. You know you'll not get great mileage with the BB and maybe 15 with a small block, od trans, etc. Several things have to be considered.
Is this job expected to be long term?
Cost of gas and it's upward trend.
Can you afford to keep your truck and buy an econo car? (purchase, license, insurance, taxes)
How much do you want to keep your truck?
You can use one of several online tire, gear calculators to see what your setup can do with different tire diameters, gear ratios and 3 sp trans and OD trans. One online calculator is www.richmondgear.com, street calculators. Your small block should be most efficient running around 1800 to 2200 rpm, provided it's not loaded with some high rump cam and high rise intake, etc.
Our all stock 97 4wd Burb gets 19 and 20 out on the highway running 70 to75 with the 5.7. It is getting this good of mileage while running right at 2,000 rpm. Yes it is fuel injected and comp controlled but it does run easier at that rpm.

[lukecp]

I bought a used '97 Saturn for $2550 about 3 years ago....38-42 mpg on the highway, with the AC on, and around 30 in town. I've put 47,000 miles on it since then. Very hard to beat the "bang-for-buck" there...its been reliable too, I drove it from Missouri to Washington, DC (1100 miles) a few weeks ago and it never skipped a beat. It is slow and handles crappy (better handling than a truck though, lol).
I went through a similar thing at the time...add a 700R4 and/or EFI to my truck, which might get 18mpg then, or spend the same amount or money on a car that would get excellent gas mileage, and have my truck as a toy.

[67ChevyRedneck]

Keep the truck and buy an eco car. I have a Z71. The best any new fullsize does is 17-20mpg HIGHWAY ONLY (depending on what combo you get), and in 2wd trim only, but as soon as you hit any city type driving they all get 14-15mpg.

As far as the truck, I personally think a 3.07 with a 700R4 is a bit steep. You could compensate for that with a smaller tire. Even new GM trucks with OD (the 4L60 is essentially a computer controlled 700R4) don't use a gear higher than 3.23. Most come with a 3.73.

Real world example. My 67 has a 350/700R4/3.73 with edelbrock 650cfm carb and bowtie overdrives tranny kits. I've checked every tank for the past 6 months and for straight city driving (stop and go) I've gotten tanks ranging from a low of 12.7 and as high as 13.2, the average seems to be around 12.9mpg and I RARELY use OD. I manually shift the truck a lot (from OD to 3 and 3 to OD) because the 700R4 has a tendency to want to shift into OD at 40mph under light acceleration. I leave the truck in 3rd until at least 45 or 50 mph.

On the highway I can get 15 mpg at 75+mph (ok, more like 80 ) but if I keep it to 65 I can push 16mpg out of it.

No matter what you do to these trucks, they're still big, heavy, bricks.

[72 cheyenne pdx]

I say keep the 71. I know this is taboo, but if you want a truck and have good mpg, get a Toyota/Nissan compact P/U as your DD. You can pick up an older (late 80's/early 90's) for less than 2k. You will get 25+ mpg in them. If you want to stay American, then get a s10/s15, Luv, or Ranger(another Taboo). They will also get 25+ mpg.

That's my $0.02. Good luck with the decision.

[trkklr77]

i can not have a car, to useless, unconfortable, small, easily beaten up throw away, i need to be able haul parts, tools, fishing stuff, camping stuff...........

i cant really aford to keep the truck and get a gasser. i maybe going on the hook to get a loan for a newer 98+ chevy weather i sell the 71 or not.

in the next year or so [if i get the new job] i will get 50-75% increase in income, and in 6 months i will be able to control the distance i will be driving better, ei: closer to home.

i want to eat my cake and drive my chevy.

[streetstar]

Going to a newer truck isnt going to help your mileage that much --- unless you go to a new compact truck, like a Tacoma or a Colorado --- My '06 F150 only gets 14-16 mpg and cost 28 grand.

I have a truck with a 250 I6 and a 4 spd Granny gear tranny that gets better mileage than that , but any v8 powered older, 3 speed truck i have ever had got 10-12.

Think about how much gas you could buy with 20 or 30 grand (about 600 a month) -- because thats what new trucks cost.

And paying 10 or 12 grand for a used 4 or 5 yr old truck can be a rip deal too sometimes