![]() |
Register or Log In To remove these advertisements. |
|
|
![]() |
|
Thread Tools | Display Modes |
|
![]() |
#1 |
Registered User
Join Date: Jan 2018
Location: TN
Posts: 263
|
Increase in gas milage
My 69 gmc 1500 Long bed. Leafs in the rear. 307 rear end. Year old 350 crate. Quadrajet Th350gets around 12-14mpg. If I switched out the quadrajet for a Holley sniper. Installed a 700r4 different rear end gearing. Probably 3.54. What kind of fuel milage increase would i probably see. I would like to trip in to the goodguys get down next year without killing my wallet in the process. I do not want to LS swap the truck. Any other ideas to increase the gas milage? I also would like to make it be my daily for college (because who wouldn’t love daily driving a c10 ) but the few times I have Commuted in it the gas was too much to keep up with.
|
![]() |
![]() |
![]() |
#2 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
|
Re: Increase in gas milage
That's pretty good mileage. Expect less with a square bore carb. You can spend a lot of gas money trying to get a couple more MPG that you 'might' gain.
__________________
"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 ~ |
![]() |
![]() |
![]() |
#3 | |
Registered User
Join Date: Nov 2018
Location: Sweetwater, TN
Posts: 14
|
Re: Increase in gas milage
Quote:
|
|
![]() |
![]() |
![]() |
#4 |
Registered User
Join Date: Jun 2015
Location: Melbourne, Australia
Posts: 231
|
Re: Increase in gas milage
I did the sniper thing and the improvement in mileage was barely noticeable.
Not worth it in my opinion if you’re purely after mileage gains.
__________________
John 69 c20, 396, th400, dana60, ps, ac |
![]() |
![]() |
![]() |
#5 |
Registered User
Join Date: Mar 2007
Location: cincy
Posts: 694
|
Re: Increase in gas milage
Same here. I didn't change gearing still have 3:73.
__________________
There's something women like about a pick-up man 1967 c10 swb Stepside 2004 SSR 2013 Silverado swb |
![]() |
![]() |
![]() |
#6 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
|
Re: Increase in gas milage
^^^ Very good tip right there! I save 2-3 mpg by staying at 65 in my '95 truck w/OD and maybe 1 mpg doing 55-60 in my '72. I have no problem on interstates staying in the right lane. It's a speed limit, not a speed requirement.
Was that Quadrajet fresh when new engine was installed? Can't beat one in proper working order.
__________________
"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 ~ |
![]() |
![]() |
![]() |
#7 | |
BlahBlahBlah
Join Date: Feb 2002
Location: Wa.
Posts: 19,877
|
Re: Increase in gas milage
Quote:
|
|
![]() |
![]() |
![]() |
#8 | |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
|
Re: Increase in gas milage
Quote:
__________________
"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 ~ |
|
![]() |
![]() |
![]() |
#9 |
Hittin E-Z Street on Mud Tires
![]() Join Date: Nov 2004
Location: Greenville, SC
Posts: 23,090
|
Re: Increase in gas milage
You won't see much of anything at all compared to the #'s you posted. The best my truck has ever gotten with the 700R is 17 mpg - 100% highway at 60-65 mph (it's happy zone). It drops to 15 at 70-75 and I only get 11-12mpg most of the time "around town."
I did my 700R swap to get my RPM's down, but I already had a 3.73 rear.
__________________
Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride ![]() American Born, Country by the Grace of God ![]() 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! |
![]() |
![]() |
![]() |
#10 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,720
|
Re: Increase in gas milage
You can buy a LOT of gas for what a gear swap, an OD trans swap and FI costs...
You will most likely never make that up. Do it because you want to. Do it because of the performance increase but don’t think the mileage improvement will pay for that stuff.
__________________
44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
![]() |
![]() |
![]() |
#11 |
Its a Truck Thing......
Join Date: Dec 2004
Location: Sierra Vista, Arizona
Posts: 3,159
|
Re: Increase in gas milage
I am running a 3.42 rear gear with a 700R4/350 Edelbrock 600. Around town I get about 11/12. On the interstate or long back roads I can get about 16/17. Its a longbed and I drive it everyday.
There was a lot of cost to get it that way. If I do go FI it will be a Vortec swap. Only way I would add just FI is if it was really cheaper to convert. Carbs are fine if you keep them maintained. I average about 8/10 days between fill ups at about $40 a pop, but I live in a small town. Been through Dover many times..... Shoot me a PM if you want any info on the swaps.... Smitty
__________________
71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time |
![]() |
![]() |
![]() |
#12 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,217
|
Re: Increase in gas milage
The Q-jet is the best carb for MPG. Make sure it is working right & check the ign. system. Make sure the mechanical advance is not stuck or sticky. Make sure the vacuum advance is good. Experiment with timing settings. If the vacuum advance is not hooked to full manifold vacuum, try it that way. Sometimes little things can add up to 2-4 MPG. increase.
George |
![]() |
![]() |
![]() |
#13 |
Registered User
Join Date: Feb 2003
Location: Santa Ana, CA
Posts: 2,191
|
Re: Increase in gas milage
Schedule your trips so you always have a tailwind
![]() |
![]() |
![]() |
![]() |
#14 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,156
|
Re: Increase in gas milage
Cleaning it up aerodynamically will help. Lowering my S10 Blazer upped my highway mileage from 18-19 to 21-22. Getting the front air dam down within 6" of the ground makes a difference. Do a search for air dam or spoiler. Switch to smaller mirrors, remove the radio antenna. Put a cover on the bed or remove the tailgate. Put skinny tires on. Get a set of Bonneville disk wheel covers. Think salt flat racer.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
![]() |
![]() |
![]() |
#15 |
Registered User
Join Date: Sep 2011
Location: Ark City, Kansas
Posts: 3,337
|
Re: Increase in gas milage
12 MPG is good, 14 is great.
I also will ask about the tune of your Quadrajet...If yours is just stock, it's doing quite well. A dial in with Cliff's parts can help, but I would NOT touch your carb in it's current condition. All the stuff you have to do to install F/I is too much work, and too much $$$ If, you want to tey to gain some MPG, I'd buy another Quadrajet, just like yours, buy a kit and all parts needed from Cliff. He can tailor a carb to your engines exact specific needs, every time, it can make a big difference...Don't touch your current carb!!! |
![]() |
![]() |
![]() |
#16 | |
Registered User
![]() Join Date: Oct 2011
Location: Victoria, B.C
Posts: 3,794
|
![]() Quote:
....what would that be?....2-5 mpg? Next, what would those upgrades cost? carb/trans/rear diff?....$1500-2000? So you have to save that much on the fuel difference to make the numbers work. So how many miles does $1500-2000 pay for? ....500 gallons of gas? The odds of seeing that savings quickly show up to pay off the upgrades are slim to zero....respectfully. Now, if you can afford those upgrades....great, and if you want them to improve the driving experience....great, just don't expect them to help the 'bottom line' costs of the truck much. In my opinion gas mileage has been an odd and misdirecting marketing system in attempting to establish (or 're-direct') relative vehicle costs...but this has been covered before at length in other threads. All good Coley
__________________
....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500 |
|
![]() |
![]() |
![]() |
#17 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
|
Re: Increase in gas milage
In the early '70s after the gas crisis you could buy nice comfortable fullsize American cars for a couple hundred dollars. The owners were casting them off to squeeze into Japanese econoboxes that replacement parts cost 4x as much as the American cars. All to save money at the pump and make car payments while we drove cars that cost what one of those payments was, but took more gas to run.
__________________
"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 ~ |
![]() |
![]() |
![]() |
#18 |
Registered User
Join Date: Feb 2009
Location: Southern Oregon
Posts: 1,352
|
Re: Increase in gas milage
All awesome advice.
Like others have said, you are already doing well at 14 mpg. Do not expect a miracle here. I would try and tweak what you have to squeeze the most out of it. Play with the timing and keep detailed notes. Do one change at a time and chart every fill up. Make sure your odometer/speedometer is correct or find out what percentage it is off by to factor accurate milage. Consider a clutch fan or electric fan. They are worth a smidge on mpg. Synthetic oil in the diffs to reduce drag. Check the drag on your drum brakes. A cold air intake may help slightly as well, especially in the summer. Like everyone else said, keep the qjet. Learn about them. Especially the adjustable part throttle circuit. An O2 sensor may be a viable investment as well. The biggest thing here is driving slower. Keep your speed under 65. Ideally 55-60. HO455 hit the nail on the head with his info on aerodynamics. You may see a 10-20% increase in mileage with most of your current parts and minimal cash outlay. Which is always good! ![]()
__________________
1967 C10 Suburban 454/TH400/3.07's An Average Joe and His 'Burb: http://67-72chevytrucks.com/vboard/s...d.php?t=775843 |
![]() |
![]() |
![]() |
#19 |
Registered User
![]() Join Date: Oct 2011
Location: Victoria, B.C
Posts: 3,794
|
![]()
...also remember to put the air pressure up in your tires....at or near maximum always for gas mileage.
Running soft can cost you a mile or two per gallon pretty easily with the extra rolling resistance. ....oh yeah, don't forget to wax it. ![]() lol All good Coley
__________________
....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500 |
![]() |
![]() |
![]() |
#20 | |
Registered User
Join Date: Jan 2018
Location: TN
Posts: 263
|
Quote:
Posted via Mobile Device |
|
![]() |
![]() |
![]() |
#21 |
Registered User
Join Date: Jun 2015
Location: @
Posts: 890
|
Re: Increase in gas milage
I bought an aem airfuel guage lets you tune what ever carb you got properly with real world real time numbers and you can see each circuit so you know your airflow screws are right jets power valve whatever your setup . I have a holley and tend to drive 55 mostly so I set the airflow screws to give me 13.5 to 14 at idle the main jets give me a nice 12.5 to 13.5 at 55 and I set up the powervalve and secondary's to give me around 10 to 11 when I want to jump on it hard . I gained 5 to 7 mpg over using just a vacume guage . im getting 12 - 14 on a stock 1984 350 turbo 400 trans and 373 rear gears . this summer I plan to play with the timing to see if I can get a few more im greedy that way . oh I found the guage in evil bay for around 200 bucks 5 to 7 mpg will pay for it in no time
|
![]() |
![]() |
![]() |
#22 |
Registered User
Join Date: Feb 2018
Location: gilmer tx
Posts: 75
|
Re: Increase in gas milage
I drive my duramax for mileage or my car. These old trucks are just for fun. They were built when gas was .25 a gallon and are an aerodynamic brick. Like others have said just drive it and enjoy. My 72 C20 gets around 12 or so and that's about normal for these things. If you want mileage then go to a newer engine with FI.
|
![]() |
![]() |
![]() |
#23 |
Registered User
Join Date: Apr 2003
Location: NB
Posts: 3,367
|
Re: Increase in gas milage
I increased my gas mileage by 60 percent.
I take the bus Tuesday Wednesday Thursday 45 mile and hour top speed doesn't hurt either
__________________
1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD |
![]() |
![]() |
![]() |
#24 |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,200
|
Re: Increase in gas milage
Just drive slower.
That's free. K
__________________
Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
![]() |
![]() |
![]() |
Bookmarks |
|
|