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General Site Info => General Discussion => Topic started by: 77c10diesel on November 10, 2010, 02:24:30 pm
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I may be selling off my 2003 Cummins Dodge and need to get something to drive to work. I gave the 77 C10 Diesel to my son, and it will be done soon I hope.
So, other than going with another Diesel, how would be the best way to make a high MPG truck. I know there was a special optioned truck for 81-82 that had a 6cyl and a manual trans that got 30 MPG, but details seem hard to be find and verify.
I am thinking I would look for an 81-87 (best aerodynamics) with a manual trans. What transmissions were available? Any 5 speeds?
As for the engine, maybe a 305 with a very mild cam, dual plane manifold, 4 brl and some shorty headers?
Add an MSD and a K&N filter. Drop the truck a few inches and keep the tire size close to stock.
What would be a good rear ratio?
I know EFI would be the way to go, that might come latter, but what other suggestions would you have if starting from scratch to build for MPG?
I do not have the truck yet, so I can look for what I want, and around here they are plentiful and cheap. And, yes I know, 88+ are better for aerodynamics and FI, but they are ugly to me. It will be a daily driver 2wd, 1/2 ton mostly long back roads and freeway.
Thanks for any input you can give, or other posts on this subject, links, etc.
Scott
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350's would be the best IMO. I firmly believe if the engine is geared right and is tuned you should be able to reach 20mpg. A lot of folks call me a liar when I tell them I have gotten as high as 16 with my 3/4T 454. If the engine isn't working hard to keep the truck going down the road that is what would yield the best results. I had real good results in a 1972 C-10 using a 2 bbl which I had a variety of jets that I kept going down in size, kept checking the spark plugs and the tail pipe for color. The truck had a TH350 and 3.08 rear gears running 235 75R 15's and got 16-17mpg. The 72 was stock height and a lot heavier than a 81 or newer. A rare optioned manual trans was a 4 speed OD and paired with a 2.73 rear end and 215 75R15's. Of course the 305 was the V-8 of the 1/2 tons. If I was going to build one I would have a 2.56 rear end and a 4 speed w/granny gear as opposed to an overdrive which is very hard to find. My $.02
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Yea I seen an old article where they tested the 4.3 v6 out v. the 305 and the differences in mileage and power were very slight. I would say go with a 350.
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Believe it or not, as a first move, i would be looking to move down to say 195/75r 15's or even 195/65/60 r 15's and aluminum wheels. Also, brand makes all the difference in the world; i would be looking at Michelins.
Remember that these trucks weigh at least 3800 lbs and are large. They simply are not high mpg vehicles. The only way(s) to get more reasonable mpg is to go diesel, move down on cubes (v-6 or inline) or go hi compression and water injection.
Pls see my ongoing scientific thread regarding mpg:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=8474.0
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Use a quadrajet on a V8, if you don't want TBI. I think the manual will win out for mileage in most any case except highway cruising, where the 700r4 with OD would keep the rpm's down some. I read somewhere that when they switched the front clip design in 81 it reduced something like 300 lbs from the vehicle. Travel light and keep it tuned up.
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I know that I will never see 30 MPG out of a full size Chevy/GMC truck. That is not what I am after. But, I also want to be able afford to drive it. Right now my 7000lb Dodge gets 20-21 MPG on Diesel. Diesel is about $.20-$.30 more per gallon, but it varies, sometimes its the same as gas. The problem is the added $380 payment on that beautiful truck. So, I can afford to use a little more fuel and still save some cash.
I am thinking I still need a 3/4 ton and may just go with a 6.2L Diesel, but I like the Idea of a second truck just for commuting, I hate little cars.
I swapped a 5.7L into my sons 77 just for fun, it was going to be mine, but he decided that he wanted it more than his 62 Corvair Monza.
Anyway, any more suggestions? I am open to all.
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I consistantly have gotten 18mpg never more or less city or hwy from my 82, LWB, 305, sm465, 4X4, q-jet with 31X10.5X15 bfg all terrain t/a's.
Only work I did was a tune up with a new complete dist. and spent a lot of time getting it to run just right(re-routing/replacing vacuum lines, timing etc).
With my '80 SWB, 250 I-6, sm465, 2WD, lowered 2/4, 275/60/15 firestones, I get 16-17 without as much power.
from that experience I would go for a 305 over a 250, I don't really really know why the 82 did so we'll on mpg. seems like I should have luck to see 15.
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Diesel is going to yield the best mileage in any truck, close to 20mpg city (25mpg highway) is not out of the question with one. I would get an 700R4 with it and gear it with 3.08 if all you are doing it driving. If you want a manual, get a NV3500 out of a 88-up pickup.
81-87 truck got lighter because of several reasons, sheetmetal not being the biggest part, and it started in 1980. Frame crossmembers were no longer solid, glass was thinner, power motors were smaller/lighter, brake rotors on the STD were thinner and had less drag among other things.
My high mileage 305 in my 87 pickup gets 22mpg on the highway and 17mpg in the city.
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i never thought i'd say this since i love older vehicles (when I say older, I mean 60's and 70's) with points and carbs and no computers. But since having my '91 3/4 ton 5.7 tbi sub 4x4, which, btw, gets me 17 mpg hwy (yes that's correct--w/33's on a 3.73 and 4l80E trans) and around 12 city, I am now sold on TBI engines over carbs. I have always been the one who likes to change and be able to adjust things (ie: idle), but, the reliability and eifficiency of a tbi is great. So I'd be in the hunt for a '87+ truck which has tbi. And, I agree about the 5.7. Never had a 305, but, to be a pick up truck, I can't see going smaller than a 350 so you won't have to keep your foot on the floor to move the heavy metal.
With that said, is your way to work mostly highway? I have seen a few posts here say taller rear gear and OD etc...But, if you drive, say roughly 50% city or more, I would'nt opt for such a tall ratio drive line because, again, you'd have to keep your foot in the accelerator to get 'er going so often. If it is mostly hwy miles, sure, go with the taller rear gear and OD.
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Right now my drive is 90% back roads, 45 MPH or higher, all straight roads, no curves and its about 20 miles. I may be changing jobs to a place about 1 hour away, but same kind of roads.
I do have another 5.7l diesel, but I think I would rather use a 6.2l or some other diesel (Isuzu, etc).
I think what I will end up with is 2 trucks. One will be a Crew Cab 3/4 ton with a 454 or diesel, the other will be my commuter. I need something to haul the 5th wheel, and kids, the other to just drive. I guess a Diesel crew cab might be able to do both if driven easy .
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Get an 81 or up shortbed truck, they're lighter and more aerodynamic than a comparable pre-81 truck. Make sure you have the air dam on the front bumper. keep a 28" or smaller tire, and keep them fairly skinny. Also use the lightest duty suspension to save weight. Barebones trucks weigh a good bit less than silverados with all the insulation, power options, AC and such. Get an electric fan. Nix the AC, maybe the power steering if you have arms like the hulks waist. Lower the truck some. Make sure all the body panels like up well. If you have a V8 or diesel, maybe keep the AC, as I get better mileage with the windows up and the AC going than I do with the AC off and the windows down. They don't wind-tunnel trucks with the windows and tailgates down. ;D Install a vacuum gauge in the dash <-That Really does help! use aluminum wheels and light duty tires to save weight. use a manual trans. have a fleetside bed. use a single tank setup so you aren't driving around with twice the fuel weight. Get a cold air kit and hi flow air filter. use full synthetic oil. get smaller mirrors. buy higher offset wheels like off of a newer truck, as the deep rally wheels are bad for air flow, as thats why all the new cars have no dish wheels on them. get a trans with a lockup converter. Open up the spark plug gaps approx. .010 from stock. roller cam/rockers. don't usehi volume oil pumps or water pumps. benchseats weigh less than bucket seats. dont dynomat anything. use lightest GOOD grease you can in the wheel bearings. use lightest weight GOOD oil you can in the differential. MSD type ignition box- thats a big one. Use resistor type spark plugs. if you have overdrive, Keep a single exhaust system - 2.25" to 2.5" with a chambered type muffler.
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Eat salads instead of Big Macs.... Lol I had to
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Get an 81 or up shortbed truck, they're lighter and more aerodynamic than a comparable pre-81 truck. Make sure you have the air dam on the front bumper. keep a 28" or smaller tire, and keep them fairly skinny. Also use the lightest duty suspension to save weight. Barebones trucks weigh a good bit less than silverados with all the insulation, power options, AC and such. Get an electric fan. Nix the AC, maybe the power steering if you have arms like the hulks waist. Lower the truck some. Make sure all the body panels like up well. If you have a V8 or diesel, maybe keep the AC, as I get better mileage with the windows up and the AC going than I do with the AC off and the windows down. They don't wind-tunnel trucks with the windows and tailgates down. ;D Install a vacuum gauge in the dash <-That Really does help! use aluminum wheels and light duty tires to save weight. use a manual trans. have a fleetside bed. use a single tank setup so you aren't driving around with twice the fuel weight. Get a cold air kit and hi flow air filter. use full synthetic oil. get smaller mirrors. buy higher offset wheels like off of a newer truck, as the deep rally wheels are bad for air flow, as thats why all the new cars have no dish wheels on them. get a trans with a lockup converter. Open up the spark plug gaps approx. .010 from stock. roller cam/rockers. don't usehi volume oil pumps or water pumps. benchseats weigh less than bucket seats. dont dynomat anything. use lightest GOOD grease you can in the wheel bearings. use lightest weight GOOD oil you can in the differential. MSD type ignition box- thats a big one. Use resistor type spark plugs. if you have overdrive, Keep a single exhaust system - 2.25" to 2.5" with a chambered type muffler.
Good advice, the short wide 81+ trucks are not easy to come by, I have seen short step sides. May have to go with the salt flats/Rat Rod look with the salt flat disks narrow wheels and tires, lowered etc. That OK, I like that look anyway.
How hard is it to install a later 5 speed in an older truck?
Seems like it might be worth getting an 88+ parts truck to get the EFI and 5 speed out of.
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I got between 24-25 mpg with this setup, and its no word of a lie, no one ever believes me until they come for a ride with me and see for themselves. I bought this truck as a DD while I fixed up my 4x4 and its still my DD 3 years later. Its an 84 1/2 ton longbox. It has a 305 (stock as far as I know), with a 700R4, and a 3.07 posi rearend. 235/75/15 tires on factory rally rims. Almost all of the factory emissions crap is still on the motor, and it has a quadrajet on it. All I ever did to it was routine maintenance. Unfortunately its lacking a little these days as I've put MANY miles on it and it could use some love. But it still gets around 20 mpg or so. As for the power it has lots, no need for a 350, when properly tuned and in good shape these engines in these lighter trucks are great.
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I got between 24-25 mpg with this setup, and its no word of a lie, no one ever believes me until they come for a ride with me and see for themselves. I bought this truck as a DD while I fixed up my 4x4 and its still my DD 3 years later. Its an 84 1/2 ton longbox. It has a 305 (stock as far as I know), with a 700R4, and a 3.07 posi rearend. 235/75/15 tires on factory rally rims. Almost all of the factory emissions crap is still on the motor, and it has a quadrajet on it. All I ever did to it was routine maintenance. Unfortunately its lacking a little these days as I've put MANY miles on it and it could use some love. But it still gets around 20 mpg or so. As for the power it has lots, no need for a 350, when properly tuned and in good shape these engines in these lighter trucks are great.
1) Is this the LE9 engine?
2) Cancel my previous comments; i now feel the best way is to look for a diesel pickup(even though you said other than diesel.....)
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my 82 burb 3/4 ton 350, sm 465 trans, 3.73 gears, 235.85.16s gets 16 city 20 hwy
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Whats an LE9? And yes the diesels do pretty well, they're just more expensive to repair.
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Whats an LE9? And yes the diesels do pretty well, they're just more expensive to repair.
Basically a "high" (9.5-1) compression 305 from the factory----you said your's was stock as far as you knew.........
http://en.wikipedia.org/wiki/Chevrolet_small-block_engine#305
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Oh thats very possible, its quite a peppy 305. Is there any way of telling if thats what I have. ???
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my suggestion is to look into adding propane injection to a 81+ 6.2 or 6.5 turbo diesel c or k truck. whille there is a cost adding this system, it is capible of increasing the efficency of the diesel engine and increasing the mpg. Diesel Power magazine had a competition between several build diesel trucks, one of them was a duramax chevy truck with propane injection, on the controlled mpg run it averaged an amazing 45mpg. we have a 85 k10 with a 6.5 banks turbo in it. 700r4, 33 1250r15, and using royal purple syntethic lubs. we consistently get up to 22+ mpg hwy by driving conservatively. i am very interested in the propane injection system, but am still doing research on the subject.
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A lot of folks call me a liar when I tell them I have gotten as high as 16 with my 3/4T 454
Zeig, i beleive you. we have an 87 454 r30 dually that we were getting 16 miles with it too, just bob tailing though!
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A lot of folks call me a liar when I tell them I have gotten as high as 16 with my 3/4T 454
Zeig, i beleive you. we have an 87 454 r30 dually that we were getting 16 miles with it too, just bob tailing though!
Thanks... course pulling my car trailer it drops to 11 and if I push it on the highway it gets thirsty. She likes 55-60 best.
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usually run it between 2500 and 3000 rpms. thats its sweet area. it drops down to around 11 or 12 hauling our flat bed and horse trailer.
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Someone mentioned earlier the 4.3 engine and for just a plain DD that sees light duty...a carb'ed 4.3 and stick with a 3.08 would be just fine. Our family ran two Astro vans for years with a TBI 4.3 / 700R4 and I swear it was a 2.79 ratio. Plenty of low-end torque to get rolling or haul a load of 5 people and car parts...but on the highway it would get 25 mpg consistently. We never towed with them, but they hauled plenty of cargo and one lasted 280K before the motor needed work. Only turned about 1800 rpm on the freeway. I'd recommend the trusty 4.3 to anyone.
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Just get a 4.3L S10. I had one in highschool and it did better than my 3/4 ton and was still able to haul several cars on a single axle car hauler. Hauling the cars was all she wanted but she still did it just fine.
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I've got 2 Chevy Suburbans. The 82 plain Jane Suburban 2 wheel drive, 1/2 ton, 700r4, 3.08 gears, came stock with the 6.2 diesel. It would constantly get mid 20's on the highway but it was so low on power that it was a safety concern. So I installed exhaust headers and dual 2-1/2" exhaust and a non EGR J code intake manifold. Power went up considerably and mileage went up to 30 mpg on the freeway at 55-60 mph. If I drive 70, mileage drops off quickly to about 24 mpg. The 6.2 diesel can be built for excellent fuel economy but several things are needed to get there. The most important thing is heads with small precombustion chambers. The older 6.2 heads came with small precombustion chambers but later on, power became more important than fuel economy so larger precombustion chambers were installed. So power went up and fuel economy went down. That said, the newer heads with larger precombustion chambers can have small precombustion chambers installed to gain that efficiency. The next important thing is a good free flowing exhaust. Then next would be free flowing air filter and Non -EGR J code intake manifold. Not having free flowing air flow into the engine just causes it to make black smoke rather than make power. Also important for fuel economy is a tall rear end like 3.08's or 3.42's and tall and narrow tires that you can pump up to 50 psi. The 1982 stock 6.2 came stock with 135 hp and with my setup, I'm probably running right around 170 hp. It's not much but it gets you where you want and sips fuel.
The other Suburban is a 1990 that now has a 1989 VE pump Cummins engine. This Suburban is 3/4 ton, 3.73 gears, 4 wheel drive and has all the bells and whistles. Behind the engine is a 6 speed NV5600 manual and gear vendors auxilliary overdrive. RPM's at 65 mph is 1320. It also has larger oversize tires and a 2" lift. At 60 mph, I get 26 mpg with the rig. It doesn't get quite the fuel economy of the 82 Suburban but it weighs a lot more and has a lot more power. Even with 10k pounds behind it, you don't slow down on the hills and it gets better fuel economy towing a heavy trailer than the 6.2. However, for solo driving, it is overkill. Way more power than you really need.
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to me the extra cost of Diesel just doesn't make up for the difference anymore, Use to be it was lower than gas, but now its quite a bit more than gas,and I thought it was a 305 they had in 80 or 81 that they designed special for fuel mileage. had a good compression ratio somewhere in the lower 9's and a good qjet, might have had some steep rear gears etc its around here somewhere.
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I know. give me a cummins motor. and i'll give you a 305
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My trouble is that I own a Cummins motor and can not afford it. It an 03 Common Rail that makes insane power, there is no end to the power it has. However, the $400 a month payment is killing me.
I do have a 77 that I swapped an Olds 350 Diesel into, but it is not finished yet. It is for my son and I hope to see 28-32 MPG out of it, but we'll see. (just no towing with it!)
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I had a buddy with a 93 suburban with a 454 4l80e it would get 16 empty but even if so much as a cricket jumped on the trailer hitch it was down to 11 ..lol
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The 6.2 diesels do well enough for High mpg without modification (Get rid of EGR and use dual pipes helps for sure). I have a dual exhaust 6.2 with a 2.73 rear and a 700r4 overdrive transmission. I do not baby my truck for mpg's. I am just as likely to hit 85 mph as to stay at 65mph. So when I say I never get less than 22 mpg on the highway believe it! I know I could get 26+ if I tried but that would require concentration and ruin all the fun of saving 5 minutes. I also get 15-16 mpg in the city. And I mean Washington DC, stop and go traffic where the general speed limits on main thoroughfares is 25 mph! So my combined city/hwy is 18-20 mpg. While my low mileage Humvee engine was being installed I borrowed a 1995 Dodge Ram 3500 w/360 magnum v8 & dually tires. Averaged 8-10 MPG. If I stayed in town hauling a load or my foot got heavy it got down to 6 mpg!! I was sure glad to get my diesel back. And diesel costs are typically below premium, so I figure less than 10% added pump cost for 30-50% better mpg. The increased costs of oil/filter changes are offset by relative lack of tune-up issues and longer term reliability IMHO. Further, despite all the naysayers, I believe diesel will be the last internal combustion holdout. We can make real biofuel for diesel out of weeds. All we need is a solvent and vegetable oil. Try that in your gas engine. Finally, I have never owned a full sized Van or pickup that averaged over 15 mpg before and I have owned six and driven more than I can count. Working on this '86 Sierra is a breeze too. I will never own anything else as a daily work truck other than a 84-87 Chevy/GMC with a 6.2 diesel. I ;D them!