Fuel Efficient '72 Chevy K20

[brad_man_72]

Originally Posted by WIDESIDE72

Sorry, dont know how else to say this. Hope it doesnt hurt your feelings.

You're free to believe whatever you like, no feelings hurt, 17mpg with truck pulling the boat down the highway 70mph, 18mpg with truck empty (playing a bit), 28mpg driving the miata like a rented mule most of the time.

The cheapest way to buy less gas and own a classic truck is to buy a beater, I needed a beater that id actually drive (5 speed, rwd, posi, convertible).

[capev86]

on my 72 Suburban C20:

originally:
307 2 barrel
3 on the tree
4.57 gears in the HO52
10-11mpg

mods:
Edelbrock Perfomer Intake (idle-5500rpm)
Rochester Q-jet
4.10 gears
14-16mpg

with the steep gearing and the aerodynamics of a brick (even modern trucks can't escape this), best mpg is attained at a steady pace around 50mph. future plans call for installing another 3 on the tree 7 bolt Saginaw with a Borg Warner overdrive on the back end. hopefully i will be able to top 20mpg on the highway once i get my other transmission installed.

[RichardJ]

I can't agree with you guys on the Gear Vendors unit. I guess they have their uses, but I don't see this as one of them.

This pile of parts is $3,100 + tax + shipping and it doesn't end there. I don't see the return.



A good 4spd auto with OD would be better or for that price you should be able to find a 6l80E and they have double over drive.


>>brad man 72
After my ls swap and beater I get about 25mpg combined.<<

We're to understand you are combining the mileage of your truck with your jap junk?
You must work for the Government?

>>a $1000 beater for when you don't have to drive the truck.<<

Don't have to drive the truck? I'm sorry, I don't get that either.
I enjoy driving my old truck. It's the Vette that gets 20-25 mpg and sits on a trickle charger.

[capev86]

the gear vendors units with their mild overdrive ratio are better suited to an old motor home that never had overdrive or a tow rig that rarely runs solo. with the purchase price plus all the custom fab work required to install (shortening the drive shaft, etc) it will take a LONG time to get any kind of return on investment. what they are good for is as a gear splitter like the HD trucks with a 2 speed rear.

[engineer_gregh]

This is a great thread. I have a 71 long bed with the following; 3:08 non-posi, turbo 400, BB 402 bored .30 over, Comp Cam 268HE, headers, Edelbrock RPM intake with an Edelbrock 750, all freshly rebuilt and tuned properly. I average 9 MPG around town and 12 MPG on the freeway. I just did a 500 mile round trip run this past weekend. Along with the gas mileage other concerns are highway speeds, RPMs, and drivability. I kept the speed constant at 65 MPH on the freeway to average 12 MPG and was at ~2400 RPM's. I think after this trip I would like to add cruise and should look for a way to add an overdrive tranny like a 700R and up the rear end ratio to 3:73. At 65 MPH on I-75 you're a snail, and trying to hold constant speed without cruise is difficult (maybe I'm just getting old). Just my thoughts.

[msgross]

buy a motorcycle...

crunch the numbers and see what the return on investment is "if" you happen to raise the MPG by 10%. I doubt that it will py or itself in he next decade unless you drive that truck 20,000km a year. If that's the case then get a cheap fuel efficient car/motorcycle and enjoy the truck as is. Better use of money IMHO.

My 2005 Tahoe barely gets 20mpg on road trips. That's an LS engine, 4L60 tranny, 3.52 (or 3.42) gears and new Michelin street tires. Do a body swap.

[brad_man_72]

Since all of my gas money comes out of my pocket yes I take all of the vehicles I drive into account. So now I have more fun vehicles to enjoy and more money in my pocket to mod my truck.

My $800 jap junk beat a 450+hp 69 camaro with suspension mods and sticky tires around an autocross course.

For me getting better mpg is about saving money, I don't really see any other reason, maybe I'm missing something. Other than a decent tune and swapping to an od trans when your trans goes out anything else will take forever to pay for itself.

[capev86]

no matter what you have for an engine and gearing, you got to keep the speed down for the best economy. with a truck there is a lot of weight being pushed down the road and air to displace and that air resistance increases exponentially as speed goes up. even the most efficient and slippery shaped cars get best fuel economy well under 60mph. and driving a little 4 banger car as a daily driver will save you economy and wear and tear on your pride and joy. i couldn't imagine driving my truck to work every, even if i do have a 5 mile commute. i have a 97 camry for a salt sucker and i'm resto modding my 86 Aries wagon for use as a sporty summer car (2.5 turbo inter-cooled, 5spd, big brakes, sporty suspension, etc).


12mpg isn't bad for a big block truck. a lot of bb trucks struggle to clear 15 even with an overdrive. yes the 3.73 with overdrive will be better than a straight 3.08 gear in regards to performance and economy. i actually like the 3.42 gears in my dad's 99 Suburban C1500. 2wd, 350 and overdrive and he has managed 22mpg.

[engineer_gregh]

capev86 you're dead on. Its more about enjoying the drive than gas mileage for me. I want to be able to take a 200 mile trip a couple of times a year when the weather is nice. My truck goes to shows during the summer months but I also enjoy it in the winter. Its not a daily driver and hopefully never will be but man its sure fun to drive!! I'm considering the OD and 3.73 to be able to better flow with traffic patterns in TN and GA on the interstate, which is 70 to 75 MPH.I didn't run more than 65 MPH because of the RPM's. BB and high RPM's for sustained time don't go well together.

[62k10&84k20burb]

I dont know, my grandpas c20 with a 250, and 4spd pulled about 17 mpg

[msgross]

Originally Posted by 62k10&84k20burb

I dont know, my grandpas c20 with a 250, and 4spd pulled about 17 mpg

This is a K20 though...

[1971 cheburban]

That my friend is what we call a conundrum, just kidding, four cylinder cummins, nv5600 and a 3 speed splitter would be efficient, if you wanted to move put it in low range, low gear under drive and pull your house away, then on the highway you could do 90 rpms at 70 mph and you could drive that mother******* like a semi

[Coley]

The cost of gas debate always illicits some great responses.
Gas mileaage been well marketed as being a major vehicle cost...when really it is a minor vehicle cost in most cases.
The extreme case of cost is when you commute extensively for more than 1/2hr in any direction to and then from work at which point you should be running an economy car.
The major cost of a vehicle is in the purchase (often financed) and resulting depreciation. These losses make the gas mileage costs look like a walk in park usually. A quick analogy is thats its like spending a half million bucks (or more) on a new house because it has an efficient furnace...LOL...even a house is a better investment...LOL.
We are fortunate that these trucks are at a point where they don't depreciate....actually they probably pick up a buck or two in value everyday which helps offset the gas they do use.
My '72 is actually the most cost effective vehicle I own at the end of not only the 1st year...but the 3rd and 5th.
My two bits.
Coley

[driller35]

72 K10 Shortbox
350- 4sp 3.73 posi , numbers matching original 76,000 orig miles
gearvendors overdrive
consistently gets 19.5 mpg hiway

[72MARIO]

Originally Posted by driller35

72 K10 Shortbox
350- 4sp 3.73 posi , numbers matching original 76,000 orig miles
gearvendors overdrive
consistently gets 19.5 mpg hiway

Is that to a Canadian gallon ? or U.S ?

[driller35]

That's imperial measure Canadian,

[Lemield]

My K20 gets 17-18mpg in town and 23mpg on the highway. It has a 6.2 turbo diesel and a ranger overdrive, SM465 4 speed transmission.

[burnin oil]

Originally Posted by 1971 cheburban

That my friend is what we call a conundrum, just kidding, four cylinder cummins, nv5600 and a 3 speed splitter would be efficient, if you wanted to move put it in low range, low gear under drive and pull your house away, then on the highway you could do 90 rpms at 70 mph and you could drive that mother******* like a semi

My old DD was a 95 Dodge 2500 4x4. Had 3.55s with a 6spd manual and a Cummins. With alot of stop and go (think 45 minutes of concert traffic each morning) It got 16.5 MPG pushing 700 RWHP.

My MPG fix is take the other halfs TDI Jetta 50+ every tank and it isn't stock either.