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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: cwilson jr on April 03, 2009, 01:25:57 pm

Title: MPG
Post by: cwilson jr on April 03, 2009, 01:25:57 pm
does anyone know what these trucks are "supposed" to get?  i have an 85 k10.
Title: Re: MPG
Post by: biggietalls on April 03, 2009, 02:25:55 pm
need to put more info about it then that
Title: Re: MPG
Post by: 79K20 on April 03, 2009, 03:16:45 pm
Who freakin' cares! We're not talking about a gas-sipping Prius here...

Mine has a sticking-choke-quadrasuck and 4.10 gears... I never plan to check the MPGs!
Title: Re: MPG
Post by: eventhorizon66 on April 03, 2009, 03:24:31 pm
Who freakin' cares! We're not talking about a gas-sipping Prius here...

Mine has a sticking-choke-quadrasuck and 4.10 gears... I never plan to check the MPGs!

LOL.  My truck with stock 350, Edelbrock carb, 700R4, 3.73 gears, 29" tires gets around 15-16 mpg average (that's about 70-75% freeway; and very conservative acceleration in the city).  All highway yields 18-19 if I keep it around 65 mph max.  And I'm super-pleased with those figures.
Title: Re: MPG
Post by: cwilson jr on April 03, 2009, 03:54:35 pm
my bad.  it has a 350 in it.  stock all the way around.  normal maintenance items are in check and have been replaced not too long ago and it just seems like i'm doing a little worse on miles than everyone else.  we're talking between 8-9 in city/hwy mix and 14 on pure hwy, and i mean 100% hwy while i was traveling and without any load.  i also have a very "tentitive" style of driving which shows up in my other vehicles, but doesn't seem to make any difference in my k10.
Title: Re: MPG
Post by: VileZambonie on April 03, 2009, 04:30:01 pm
Tune it up and set your timing.
Title: Re: MPG
Post by: cwilson jr on April 03, 2009, 05:30:27 pm
it does have a "buck" in it every once in a while,which i believe is a miss in the engine.  as far as the timing how big of an issue is that?
Title: Re: MPG
Post by: VileZambonie on April 03, 2009, 05:45:25 pm
What do you mean issue? It's critical to engine performance, fuel economy and lowest emissions.
Title: Re: MPG
Post by: cwilson jr on April 03, 2009, 06:14:00 pm
i was referring to looking into it and/or correcting.
Title: Re: MPG
Post by: eventhorizon66 on April 04, 2009, 01:04:19 am
Easy peasy. ;)
Title: Re: MPG
Post by: Just-speed on April 04, 2009, 09:35:01 am
When I bought my 84 k10 it was 100% stock and was getting about 12mpg with the 305 that was in it.

Now with my 350 I get around 8 mpg. 
Title: Re: MPG
Post by: eventhorizon66 on April 04, 2009, 10:19:31 am
I should have mentioned that the figures I posted above represent a very deliberate effort for max mpg.  Acceleration is very moderate, but not so slow that I'm always accelerating.  Idling time is minimized by avoiding as many lights as possible (when practical).  Highway speeds rarely exceed 65 mph and are frequently around 60 mph.  I only achieve those figures when I make an effort to.

My worst tank while I was "tuning" the carb and ignition timing was about 7 or 8 mpg.  It involved plenty of 50% - 100% throttle acceleration, occasional WOT at freeway speeds, lots of "experimenting" with freeway cruising speed, etc.

I think that most people drive too aggressively to achieve decent mpgs.  It just puts me in stitches when I see a Pruis cutting in and out of lanes, speeding, tailgating, and accelerating balls to the wall (which looks rather pathetic BTW).  They could have saved serious coin by going with a small non-hybrid sedan and driving more conservatively.  People would rather fork over good money for the latest trend than simply improve the way they drive for free.  LOL, it kills me.
Title: Re: MPG
Post by: zieg85 on April 04, 2009, 01:18:50 pm
I am getting 10 right now.  My carb is original and is in need of a rebuild.  Choke pull off is bad so the first 5 minutes is chugging black smoke.  4 years ago when I brought it home I averaged 16 traveling 65 mph with the tailgate off.  454 4 speed with a 3.23 gear
Title: Re: MPG
Post by: cwilson jr on April 04, 2009, 09:38:25 pm
something else i noticed is when i was letting it set for a long time before i moved, i would start it up weekly and let it run for a while in park.  i then would have to eventually give it gas (still parked) to keep it from getting over the 210 mark, which i always floored it to kick down the rpms.  i forget what this is called on the carb engines.  anyway it would sound fine.  the other day while driving i pretty much gunned it from a slow pull out and while it was floored, it sounded horrible and like it was choking.  the air filter is pretty new.  could this be a bad cat?  is there a way i could tell this?
Title: Re: MPG
Post by: Stewart G Griffin on April 04, 2009, 10:12:57 pm
cw, you should get (i think based on my scientific findings) about 14.  i will give you a link to my MPG thread when i get the time.  Alternatively, you could search for it under my name.

What diff gear(s) do you have?
Title: Re: MPG
Post by: Irish_Alley on April 05, 2009, 01:46:30 am
with my 86 c10 not sure of ratio but it had a 350 and 350t i was getting 12mpg of the cheap gas and 14mpg at the high end gas pumps. now with the same motor in my 79 k20 i get about 8. just took the carb apart, its a Holley 640 or something i know its a 600. didn't rebuild, just took it apart to clean. cause i noticed a lil rust in the fuel filter so i figured i had some extra gaskets just laying around. when i took the secondary cover off it had been dry so long it had corrosion building up in it. not sure if that hurt or help, I'm sure it hurt the mpgs
Title: Re: MPG
Post by: cwilson jr on April 05, 2009, 11:00:52 am
What diff gear(s) do you have?

i have the standard axle ratio code on the options list.  does anyone know what that is off-hand anyways?


something else i noticed is when i was letting it set for a long time before i moved, i would start it up weekly and let it run for a while in park.  i then would have to eventually give it gas (still parked) to keep it from getting over the 210 mark, which i always floored it to kick down the rpms.  i forget what this is called on the carb engines.  anyway it would sound fine.  the other day while driving i pretty much gunned it from a slow pull out and while it was floored, it sounded horrible and like it was choking.  the air filter is pretty new.  could this be a bad cat?  is there a way i could tell this?

also does anyone have any ideas with this?
Title: Re: MPG
Post by: TexasRed on April 05, 2009, 11:09:11 am

something else i noticed is when i was letting it set for a long time before i moved, i would start it up weekly and let it run for a while in park.  i then would have to eventually give it gas (still parked) to keep it from getting over the 210 mark, which i always floored it to kick down the rpms.  i forget what this is called on the carb engines.  anyway it would sound fine.  the other day while driving i pretty much gunned it from a slow pull out and while it was floored, it sounded horrible and like it was choking.  the air filter is pretty new.  could this be a bad cat?  is there a way i could tell this?

also does anyone have any ideas with this?

Could be an accelerator pump issue. Have you checked the output of the accelerator pump?