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#1 |
Registered User
Join Date: Aug 2013
Location: Four Corners
Posts: 36
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What kind of fuel mileage do you get?
I drove my truck to Utah last weekend and managed 12mpg over a half tank going 70-80 with some runs faster then that, I was pretty impressed by that.
350 Quadra Jet Headers/Dual Exhaust 3.73's 4 Speed What do you get? |
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#2 |
Registered User
![]() Join Date: Dec 2015
Location: Holland Mi.
Posts: 302
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Re: What kind of fuel mileage do you get?
On a 200 mile trip last fall, some interstate at 65-70, some 2 lane at 55-60, and a little around a small town, I got 18.3 mpg. Couldn't believe it, I thought the gas guage was broken until I refilled the tank when I got home. That was my '70 C10, 350, 1977 Olds Quadrajet, headers and 3speed manual. I was going to replace the carb with correct Qudrajet but after that trip I have left it alone. Most of the other highway trips I have taken with that truck, I was towing our 18' Chris Craft and got about 12 mpg which I think is still really good.
Last edited by Ed F; 05-23-2016 at 09:26 PM. |
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#3 |
Registered User
Join Date: Dec 2009
Location: bisbee, arizona
Posts: 1,529
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Re: What kind of fuel mileage do you get?
68K20 327 4bbl......7-9 mpg with 456 gears
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#4 |
Registered User
Join Date: May 2016
Location: Henderson NC
Posts: 975
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Re: What kind of fuel mileage do you get?
I just installed a GM L31-R crate engine in my truck. I have a Holley 750, long tube headers with 2 1/2 inch exhaust out the back, th350 trans with 307 gears in the rear. I've only got a little over 200 miles on it and haven't checked the exact mileage but I'm really impressed with it. I would be surprised if it isn't getting better than 15 mpg.
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#5 |
Registered User
![]() Join Date: Nov 2015
Location: Odessa, Texas
Posts: 29
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Re: What kind of fuel mileage do you get?
69 C20 with a 292, granny 4 speed and 3.73 gears. I get between 15-17 MPG at 65mph depending on the wind.
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#6 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,647
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Re: What kind of fuel mileage do you get?
Haven't really checked mine in a very long time..... many years ago I did about a 3700 mile trip and averaged 11.5 mpg iirc. Truck info in sig, 4.10 gears.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#7 |
Registered User
Join Date: Mar 2006
Location: Latrobe, Pa. 15650
Posts: 344
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Re: What kind of fuel mileage do you get?
69CST396-Bored and stroked to a 440 with 11.1 compression, Houghes 400 Turbo transmission, 3:73 posi, 21 gallon gas tank. Tanked it up going to work which is 35 miles away at mostly 50-60 mph. Came home after a 70 mile round trip. Pulled into the garage and saw there was only an 1/8 of a tank left. To scared to do the math.
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#8 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,858
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Re: What kind of fuel mileage do you get?
12.5 MPG in my '72 in signature. The K/20 Highlander I had got the same. That truck had 400 SBC 4bbl, 4spd, 4.10s, & 315/75. All mixed daily driving
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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
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#9 |
Registered User
Join Date: Mar 2013
Location: Campbellsville, KY
Posts: 888
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Re: What kind of fuel mileage do you get?
'85 C3500, 454/TH400/4.10's, SRW, all stock, curb weight approx. 5,250 lbs.: 12.5 at a consistent 55-65 MPH on the highway, without cruise. 9.5-10.5 when towing 6-10,000 lb.
'67 C10 Suburban, 350 (close to specs of the base Goodwrench crate engine - 76 CC, 1.94 intake heads, .383/.401" cam) with Rochester 4G and iron intake, points distributor, ram's horn manifolds with dual 2" exhaust, all stock otherwise, NP435/3.73's, 30.5x10r15 tires, approx. curb weight 4,600 lbs.: 14 MPG at a steady 60-65 MPH, more like 13.3 with 4 people, a lot of luggage and a Honda 175 motorcycle in the back.
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Alex V. ------ 1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs. 1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue. |
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#10 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: What kind of fuel mileage do you get?
Pretty sure these are 12mpg, maybe 14 for a carefully driven six cylinder. You'll hear hero stories of 20+ mpg one way and so on but nothing we can do can match the efficiency of a modern Silverado, so you have to look at what they get (they're probably heavier though) and sort of set that as a reasonable maximum I think.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#11 |
Senior Member
![]() Join Date: Dec 2013
Location: Gods country East,Tn
Posts: 8,545
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Re: What kind of fuel mileage do you get?
We're dealing with 50 year old trucks with the aerodynamics of a shoe box , Just because you drop a late model drivetrain In it does'nt mean your gonna match any sold today . You really have to consider whether you want to drive a cool truck or count pennies by driving a cool truck ? If you really need to worry about gas mileage park it and buy an old Honda 4 banger to daily drive .
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![]() 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop |
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#12 | |
Senior Member
![]() Join Date: Jun 2005
Location: Winona Lake, IN
Posts: 6,286
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Re: What kind of fuel mileage do you get?
Quote:
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70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear |
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#13 |
Senior Member
![]() Join Date: Jun 2005
Location: Winona Lake, IN
Posts: 6,286
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Re: What kind of fuel mileage do you get?
I only have about 500 miles on mine since the big block swap, so I have not really checked it out yet. I got 14-15 with the 250/TH400/3.73 combo. That was mostly back and forth to work-13 mile round trip at 50-60 mph. I am hoping to get at least 11 with the 402. All stock, except mild cam and 750 Eddy carb with 1" spacer.
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70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear |
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#14 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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My 71 has factory 4:10 gears along with 6.0 4l80E over drive and it's doing all it can to 16-17 on the open highway.
I compensated that with a 42 gallon tank though! I got right at 600 miles out of one tank back in 2014 on the hot rod power tour without running the AC at all driving on interstate the whole time coming home from Dells Wisconsin. I had some left but I had never driven it that far so I got scared and filled up.I made it home on the one fill up. That's 950 miles I drove straight through that day. I left at 11am that morning and at 3 am next morning I pulled into my garage in Liberty! About 14 hrs total That was stopping for a friend who blew a distributor cap out to and finding a parts store for him. Fixed it on the side of the interstate! Several bathroom stops to. ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#15 |
Registered User
![]() Join Date: Mar 2005
Location: Jurupa Valley, Ca
Posts: 1,210
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Re: What kind of fuel mileage do you get?
1970 C20, 350 4BBL TH350 4.10 gears 10 mpg doesn't make a different how I drive.
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Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC |
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#16 |
Senior Member
![]() Join Date: Aug 2014
Location: Sandy, Oregon
Posts: 2,376
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Re: What kind of fuel mileage do you get?
I have a 72 with rebuilt (but orignal engine) 350 small block, th350 and 3:73 gears and at 60 I'm getting about 17
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My dad always says that HEI distributers are pointless... •1972 Custom/10 Deluxe. My first truck and I've had it since I was 7. Tilt, tach, AM/FM, 350, deep dish rally's, original paint and an increasing amount of NOS jewelry. It's always taking my money.. •1967 c10 with tach, dropped 3/5 on deep dish rally's •1972 Cheyenne Super. Sold |
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#17 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: What kind of fuel mileage do you get?
I presume that's highway - I doubt these trucks could come near that in city or mixed driving, at least not when modern trucks are putting in 12 or so City.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#18 |
Registered User
Join Date: Apr 2012
Location: A Sunny Place For Shady People
Posts: 468
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Re: What kind of fuel mileage do you get?
69 C-20 350ci/TH400 with Gear Vendors OD, 4:10 rear
Need to log this stuff after the next fill up, and do the math. Usually put about 12g after 2 weeks of driving to work an running errands.
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Chris '69 C-20 '04 Jeep TJ |
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#19 |
Registered User
Join Date: Jul 2010
Location: MD
Posts: 1,937
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Re: What kind of fuel mileage do you get?
Another MPG thread if interested:
67-72chevytrucks.com/vboard/showthread.php?t=548916 As for me, I get about 8-10 mpg around town. c10 long bed step side, 250 engine, 1bbl carb. Not stellar mileage, but it runs great and I do get plenty of smiles per gallon.
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1969 c-10 Step Side Long Bed. I-6 250cid = ![]() |
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#20 |
The Niner
![]() Join Date: Nov 2010
Location: Broad Brook, CT
Posts: 2,494
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Re: What kind of fuel mileage do you get?
69 C/20 with 350ci, TH400, and 4.10 gears, I get 11-12 mpg
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"A good racer is one whose head is in communication with his balls." - Richie Evans 1970 C/20 - 402/TH400/3.54s - 74K miles 2003 GMC Sierra 2500 - Wheatland Yellow Niner Progression Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=697183 Classic Trucks article: https://www.motortrend.com/features/...et-c20-driven/ |
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#21 |
Registered User
Join Date: Mar 2006
Location: Latrobe, Pa. 15650
Posts: 344
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Re: What kind of fuel mileage do you get?
At 50-60 mph, my tach was fluxing between 3000 and 3700 rpm. I would watch the road and look down at the gas gauge and the needle moved an 1/8 of a tank. I would continue to watch the road for a little bit and look down and the gauge moved another 1/8 of a tank. Yes, I looked for leaks and any gremlins sucking on straws. Nothing. The next time I drove it to work, I never went above 50 mph. Had a 1/4 tank when I got home The first trip was a whole lot more fun. Isn't that what this is all about, fun? I'm NOT complaining.
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#22 |
Senior Member
![]() Join Date: Jun 2005
Location: Winona Lake, IN
Posts: 6,286
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Re: What kind of fuel mileage do you get?
Yep, fun is exactly what it's about for me. If I were worried about mileage, I would not have put in a big block.
__________________
70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Power windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear |
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#23 |
Registered User
Join Date: Mar 2015
Location: South of Pittsburgh
Posts: 428
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Re: What kind of fuel mileage do you get?
67 C10. 496 BBC tremec 5 spd with 3.73s. Haven't got it out on the highway to try out the OD yet, but in town it gets 6
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#24 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: What kind of fuel mileage do you get?
I believe the question in the olden days for my truck was "How far can you make it with the camper and big block and THREE full fuel tanks?", but I took out the two spares at restoration time.
I actually would have kept them if I drove it enough that the gas wouldn't all go stale, but I figured I'd never reliably burn 60 gallons in mine.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#25 |
Registered User
Join Date: Sep 2012
Location: SoCal
Posts: 529
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Re: What kind of fuel mileage do you get?
L33 5.3L
4L60e mid length headers CAI Blackbear Performance Tune 3.42 w/Eaton posi currently 80% highway 20% city I see roughly 23mpg |
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