"IDROVEAPICKUPTRUCK" (idroveapickuptruck)
09/15/2014 at 21:53 • Filed to: None
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"IDROVEAPICKUPTRUCK" (idroveapickuptruck)
09/15/2014 at 21:53 • Filed to: None | 1
| 29 |
So I bought a '85 stepside C10 with a 454 swapped into it a few months ago. I'm planning on finally putting some work into it in the next month or so but I had a question. I wanted to use this vehicle as my crosscountry-mobile a la roadkill muscle truck, but just how terrible of fuel economy can I expect? It's a 454 out of a motorhome with some LS5 oval heads swapped on backed by a turbo-400 and 3.08 rear gears. I'm not expecting 20mpg or anything but is even like 15mpg possible on the highway with a decent tune?
Thanks oppo.
Jordan and the Slowrunner, Boomer Intensifies
> IDROVEAPICKUPTRUCK
09/15/2014 at 21:59 |
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Maybe some sort of Gear Vendor overdrive unit.
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IDROVEAPICKUPTRUCK
> Jordan and the Slowrunner, Boomer Intensifies
09/15/2014 at 22:17 |
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Oof. Those are pricey. Working out the ratios 65MPH would be like 2400 RPM currently.
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Jordan and the Slowrunner, Boomer Intensifies
> IDROVEAPICKUPTRUCK
09/15/2014 at 22:20 |
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My revs are 65 at around 2600 at 12 mpg highway, so I feel your pain. Except you have power to pass...
deekster_caddy
> IDROVEAPICKUPTRUCK
09/15/2014 at 22:21 |
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if you get an OD trans (4L85E or so) you might get 18. Not worth the cost of building an expensive transmission though. I had an 8.1 in my '05 Yukon and 15 was a good day...
Edit - there's no way you will see 18.
Tohru
> IDROVEAPICKUPTRUCK
09/15/2014 at 22:27 |
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The TohruTruck was an '86 C10 longbed with a 305, Turbo 350, and 2.73:1 gears in the back. Without the topper, it got 16mpg if I stayed under 55mph. At 65 it got 10-12. The topper took 2-3mpg off those numbers.
It has been retired due to transmission failure, frame rust, and cab rust.
^ No topper.
^ With topper.
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Tohru
> deekster_caddy
09/15/2014 at 22:28 |
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I had an '86 C10 with a 305 and 2.73:1 gears in it and it couldn't hit 18mpg - it was lucky to get 15mpg if I drove it like an old man.
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IDROVEAPICKUPTRUCK
> Tohru
09/15/2014 at 22:40 |
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Okay, I'm looking at like 12MPG tops then. Wonderful.
unpredictable_swerve
> IDROVEAPICKUPTRUCK
09/15/2014 at 22:54 |
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so much want.
Hi there
> IDROVEAPICKUPTRUCK
09/15/2014 at 22:55 |
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When you see the words "big block" right next to each other, then you should not expect more than low to mid teens out of a gallon of gas on the highway, and mid to high single digits in town. Maybe 10 mpg in town if your town is tiny and has no traffic or stoplights.
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IDROVEAPICKUPTRUCK
> Jordan and the Slowrunner, Boomer Intensifies
09/15/2014 at 22:58 |
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Okay, looks like 12mpg is what I should be hoping for then... lets see how many miles it would take to make a gear venders worth it if I can get say 17MPG with it, from doing the math I would have to drive around 40,000 miles to make it worth it...
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IDROVEAPICKUPTRUCK
> Hi there
09/15/2014 at 23:05 |
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Yeah that's pretty much what I was expecting, just trying to get an idea of what my gas budget it going to be looking like.
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Jordan and the Slowrunner, Boomer Intensifies
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:05 |
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Oh, I don't have what you have, I was just saying I know how it feels. My misery comes from Japan's finest, the lovely Toyota 3VZE 3.0L V6.
wantafuncar
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:12 |
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You bought a big block chevy v8 full size truck and aren't happy with the gas mileage?No offense, but what did you expect? Its not a lightweight, fwd, compact car with under 200hp.
I like those trucks - probably a blast to drive. If you're seeking high mpg, you are probably better off swapping that big block out for something lighter & more efficient (perhaps a LS series motor). It'd take a lot fo miles to make up for the cost, but its probably the only realistic way to approach 18mpg (or more? I know some LS owners report 20+mpg, albeit in cars).
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IDROVEAPICKUPTRUCK
> wantafuncar
09/15/2014 at 23:17 |
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Dude, where did I ever say I was expecting good gas mileage, if you would actually read I was asking if 15 mpg was even possible. I know the fuel economy is going to suck, I'm just trying to get an idea of how much suck we're talking about so I can budget appropriately for my upcoming road trips. There is no need to be a dick about it.
Frank Grimes
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:20 |
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Arent those gear vendors like 3k? I would rather swap a T56 in it for that kinda money.
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IDROVEAPICKUPTRUCK
> Frank Grimes
09/15/2014 at 23:23 |
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Yeah they're really pricey. A T56 would be cool but believe it or not this is a vehicle I think is better suited to an automatic. Realistically I think I'm going to live with the super shitty mileage, I've got other things planned for this truck first. Namely a Vintage Air system and possibly air suspension
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Hi there
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:31 |
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Smaller fuel injected motor and some kind of 6 speed gearbox and 2.88 gears if you weren't going to use that 454's torque for hauling crap.
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wantafuncar
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:33 |
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wasn't trying to be a dick...
i guess i just wouldn't worry about mpg if i was buying anything like that at all. cost of entry for a big block, so to speak. you knew or should have known the mpg would suck going in (without major changes like ls swap, 6+ gears, etc).
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IDROVEAPICKUPTRUCK
> wantafuncar
09/15/2014 at 23:44 |
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Yes I knew it was going to suck, but I'm planning a 10,000+ mile road trip so budgeting is important, and knowing what to expect is helpful, even if it's going to suck.
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IDROVEAPICKUPTRUCK
> Hi there
09/15/2014 at 23:45 |
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Not worth the expense of a swap, I got the truck with the 454 already in it for a good price.
blacktruck18
> IDROVEAPICKUPTRUCK
09/15/2014 at 23:45 |
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Just give up and send it my way. I guess I could put up with it.
If you can find a 700R4 out of a c20 or c30, I think 1982's and newer but don't quote me, it will swap right in. Then put some 2.73 gears in it and you should be doing much better.
I miss my c10's. The gold one had a slightly built 350 with that same trans and gears. It did pretty decent mpg wise and would beat up on LT-1 f-bodies when they were new.
This one not so much with the mpg's. But it could set off all the car alarms.
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Tohru
> IDROVEAPICKUPTRUCK
09/16/2014 at 00:20 |
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Right. If you drive it like you're on your way to cash your Social Security check and play bingo.
Even if you threw in the tall rear axle like my truck had, you'd only pick up about 1-2mpg.
The thing that would make the biggest difference is overdrive. The best value for overdrive is a 700R4.
Your Turbo 400 (THM400/3L80) has the following ratios:
First Gear - 2.48:1
Second Gear - 1.48:1
Third Gear - 1.00:1
Reverse - 2.07:1
A 700R4 (4L60) has the following ratios:
First - 3.06:1
Second - 1.63:1
Third - 1.000:1
Fourth - 0.70:1
Reverse - 2.29:1
The 700R4/4L60 isn't quite as beefy as the THM400/3L80, but when the 3L80 got overdrive it also gained computer control - the 4L80-E. To drop a 4L80-E in the truck would require a standalone transmission controller for a couple hundred dollars.
The 4L60 gained computer control in 1992, becoming the 4L60-E. Stay away from those, they need the standalone controller.
A Camaro/Firebird from '83-'91 or an Astro from '85-'91 is a great source of 700R4's.
crowmolly
> IDROVEAPICKUPTRUCK
09/16/2014 at 10:50 |
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Big one.
What kind of carb is on it?
Engine specs? Ignition?
If it's a stock smog-era 454 you might be able to do OK even without overdrive. If it's an 850 double pumper and an aftermarket cam, break out the wallet.
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IDROVEAPICKUPTRUCK
> crowmolly
09/16/2014 at 10:52 |
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It's got LS5 heads on it instead of the peanut heads it came with. Holly 750 CFM Carb, stock ignition, stock internals.
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crowmolly
> IDROVEAPICKUPTRUCK
09/16/2014 at 10:54 |
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What manifold? Points or HEI? Is that 750 a 4150 DP or a 4779 vaccum secondary? Headers?
How would you rate the tune?
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IDROVEAPICKUPTRUCK
> crowmolly
09/16/2014 at 10:58 |
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Uh, don't really know. I'm out on an oil rig right now. I bought the thing a few months ago, it went from the trailer up and down the block once and then into my driveway. Hasn't moved since and the battery is dead.
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crowmolly
> IDROVEAPICKUPTRUCK
09/16/2014 at 11:07 |
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Ha ha. Gotcha. Well, when you get a chance, pull and post the specs and we can try and figure out a way to maximize your MPG. To be honest it won't be spectacular but it's not WOW ZOMGZ A BIG BLOCK YOUR GONNA GET 4MPG BRO.
If the right parts are there and the tune is very good you can do the best with what you've got.
Also, two things of note. I think I saw somewhere that you are planning a big trip.
1.) When you change the oil during the trip make GOD DAMN SURE you get the proper oil with ZDDP or you will be walking. Not only will modern oil lead to premature cam failure but big block chevys have a reputation for bearing failure.
2.) Price out an OD trans swap vs. the cost of fuel on the trip. If you are going 10,000 miles and getting 10mpg that's 1000 gallons of fuel. If you put a 700-R4 in with a .7 OD you would get 13 mpg, which would be 769 gallons of fuel. At $4/gal that means $4000 vs $3076.
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IDROVEAPICKUPTRUCK
> crowmolly
09/16/2014 at 11:14 |
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Thanks for the advice, especially about the ZDDP, I hadn't heard about that before and just read up on it. Will absolutely make sure I use the correct oil.
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Hi there
> IDROVEAPICKUPTRUCK
09/16/2014 at 13:35 |
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Just saying, if you want more than slight double digit fuel econ on a cross country trip, a 454 isn't the way to do it.