tips for better MPG

[DreamRyder1963]

If it makes a 20 hp different then there's no denying the switch. I doubt it will make that much of a change on mine.

RManson some corvette owners claim 30+ mpg highwaywith an ls but most people I have talked to get around 21-22mpg with ls swaps.

[RManson]

I also disagree with the 20hp claim. Think about the impact that would have on a motor that makes 200hp stock. Real world is probably more like 4-6hp.

I was actually referring to LS swaps in our trucks. A Corvette has a few advantages over a C10 when it comes to cutting through the wind and all. I'm guessing my LS-equipped '68 is probably getting around 20, but it's not stock and I haven't done the calculations with any kind of accuracy. I'm curious what a stock LS with an OD trans yields in a C10.

[i82much]

Originally Posted by DreamRyder1963

If it makes a 20 hp different then there's no denying the switch. I doubt it will make that much of a change on mine.

RManson some corvette owners claim 30+ mpg highwaywith an ls but most people I have talked to get around 21-22mpg with ls swaps.

The biggest thing I have actually seen with my own eyes is the wideband deal. A typical old street Holley is probably set up to cruise at around 12:5 or 13:1. Those are crazy rich numbers for any kind of fuel economy. Typically you can increase the primary power valve channel restrictions, jet the front side down and achieve much better cruise AFR's while still staying at about 12.5 under full throttle.

[Stu Pidd]

Originally Posted by DreamRyder1963

....some corvette owners claim 30+ mpg highwaywith an ls....

The newer Corvettes have a very tall sixth gear. Engine is running about 1500 rpm on the freeway. That's possible with lots of torque pushing a light-weight car. Top speed is in fifth gear- Sixth is only for mileage.

Not gonna happen with a full-size truck.

My data point: '68 C20, 350 w/ Edelbrock carb, SM465, 4:10 rear gets almost 15 mpg on the highway, but I keep the speed down to 60-ish to keep the rpms down. I have an NV4500 tranny sitting in the garage, to be swapped in with an LS engine soon.

LS/Vortec plus overdrive should do quite a bit better. We'll see.....

[Jack_71C10]

i saw this guy running an HHO setup in North Carolina about a month ago.
Some people swear by it, Some people call it bad science.

[i82much]

Originally Posted by Stu Pidd

The newer Corvettes have a very tall sixth gear. Engine is running about 1500 rpm on the freeway. That's possible with lots of torque pushing a light-weight car. Top speed is in fifth gear- Sixth is only for mileage.

Not gonna happen with a full-size truck.

My data point: '68 C20, 350 w/ Edelbrock carb, SM465, 4:10 rear gets almost 15 mpg on the highway, but I keep the speed down to 60-ish to keep the rpms down. I have an NV4500 tranny sitting in the garage, to be swapped in with an LS engine soon.

LS/Vortec plus overdrive should do quite a bit better. We'll see.....

I think people overstate the importance of engine RPM and underestimate the importance of wind resistance.

http://drivelinenews.com/news/how-mu...le-ratio-make/

If you look at the BSFC numbers for most engines, they actually don't make the best power per pound of fuel at the lowest possible RPM. Instead, the sweet spot is usually a good bit higher, maybe 1800 RPM for a modern V8 and 2500 RPM or so for a modern 4 cylinder.

In a carbureted car, you need to tune to get the AFR where it needs to be. If you have a rich main circuit (very common) then increasing your RPM is going to drop your fuel economy a great deal because you are bringing on the main circuit by driving faster, but this can be addressed by proper tuning.

[DreamRyder1963]

Originally Posted by Jack_71C10

i saw this guy running an HHO setup in North Carolina about a month ago.
Some people swear by it, Some people call it bad science.

Ok that one is new to me. What is it?

[Fitz]

Originally Posted by Stu Pidd

The newer Corvettes have a very tall sixth gear. Engine is running about 1500 rpm on the freeway. That's possible with lots of torque pushing a light-weight car. Top speed is in fifth gear- Sixth is only for mileage.

Not gonna happen with a full-size truck.

My data point: '68 C20, 350 w/ Edelbrock carb, SM465, 4:10 rear gets almost 15 mpg on the highway, but I keep the speed down to 60-ish to keep the rpms down. I have an NV4500 tranny sitting in the garage, to be swapped in with an LS engine soon.

LS/Vortec plus overdrive should do quite a bit better. We'll see.....

Lots of folklore here. My 2010 Corvette weighs 3300 lbs. My 67 stepside weighs 3380 lbs. The corvette gets 28 mpg at 70 mph with the revs steady 1t 1800 rpm. My 67 C10 gets 16 mpg at 70 mph with the engine ticking over at 1800 rpm on the same drive. My home to my office and back. The Corvette is a computer controlled 437 HP LS3 with the paddle shift automatic. The final drive ratio is 0.6:1. The 67 stepside uses a TH400 auto backed by a gearvendors overdrive with a final drive ratio of 0.7:1 BUT it is a ZZ572 big block with a very carefully tuned 850CFM Holley double pumper. When I can keep my foot out of it it does OK on mileage because of the drive train and gearing but if I get into the secondaries I can watch the fuel gauge fall. 100 miles of hard running will empty the 18 gallon tank. What makes the LS motor better in the MPG arena is the wideband control loop that adjusts timing and injector volume based upon inlet air flow and the O2 sensor outputs to maintain a perfect fuel air ratio. A carbed engine can't do that so you have to rely on the finesse of the guy who set it up to get the best economy. That can't be done and still maximize performance. If you put an LS motor into your truck without re-mapping the fuel air curves to match your drivetrain you will NEVER get close to the potential that engine gas for power and economy.

[Stu Pidd]

Originally Posted by Fitz

My 2010 Corvette weighs 3300 lbs. My 67 stepside weighs 3380 lbs. The corvette gets 28 mpg at 70 mph with the revs steady 1t 1800 rpm. My 67 C10 gets 16 mpg at 70 mph with the engine ticking over at 1800 rpm on the same drive. ......... If you put an LS motor into your truck without re-mapping the fuel air curves to match your drivetrain you will NEVER get close to the potential that engine gas for power and economy.

Thanks! Great to have first-hand info. Learned something here.

[davepl]

How could a 1970-era anything this heavy achieve 18 city? My wife's Escalade gets 13. My Range Rover gets 12. And those are decades newer and more efficient.

Highway I can see. But stop and go in a truck this heavy seems impossible to do efficiently without some kind of (shudder) energy recovery system.

[nightmare]

Originally Posted by davepl

How could a 1970-era anything this heavy achieve 18 city? My wife's Escalade gets 13. My Range Rover gets 12. And those are decades newer and more efficient.

Highway I can see. But stop and go in a truck this heavy seems impossible to do efficiently without some kind of (shudder) energy recovery system.

I beg to differ with this. There have been studies done that show all the "technology and safety" that goes into the newer cars also decrease fuel mileage. Besides, vehicles have gotten bigger as time has progressed. If you were to take the drivetrain of a newer vehicle (LT or LS, fuel injected), and place it in an older vehicle, you will inherantly get better mileage than the vehicle it was taken from.

Look at the weight of that Escalade. It's probably around 5900 lbs. Also look at the size of it compared to a 1972 Chevy Shortbed. It is larger, therefore, worse mileage.

Had vehicles stayed the same size as they did back in the late 60's and early 70's, but the engine technology still progressed, we would probably be getting 25-30mpg routinely.

[DreamRyder1963]

Plus our trucks really aren't very heavy. They are long around 4000 less in some cases. Pick up and single air bag or electric seat motor out of a newer car and multiply it for every corner. That adds up quick. A modern sedan can easily weight has much as an old truck.

[special-K]

Most everyone has a carb guy in their area that can do a Quadrajet right. I know I do. I also had no gauge or speedometer in my '72 K2500 for a while. I had a '72 K/20 at the same time. I was driving to the same location for work and drove one or the other truck,so I knew the exact mileage I was driving the K2500. They both were getting 12.5 mpg consistently. The trucks had differences yet it all balanced out. The K2500 has a 350/TH350,4.10s,and 12.50/33 rubber. The K/20 had a 400SBC/4spd,4.10s,and 12.50/35 rubber. Both with Quadrajets. The torque of that 400,100% lock-up of the 4spd,as well as the taller rubber proved to be a sensible combo. The truck felt like it was never working. It just rolled along with a light touch of the throttle

[i82much]

Originally Posted by davepl

How could a 1970-era anything this heavy achieve 18 city? My wife's Escalade gets 13. My Range Rover gets 12. And those are decades newer and more efficient.

Highway I can see. But stop and go in a truck this heavy seems impossible to do efficiently without some kind of (shudder) energy recovery system.

I agree with the others that old trucks are not that heavy relatively speaking. Newer trucks obviously have much better control over ignition timing, afr, even more even combustion chamber temps and better chambers. OTOH, not being subject to nox emissions means you can run an older one leaner if you really want to get some mileage out of it.

[Ackattack]

I get about 18 mpg in my 68 with a 5.3L/4L60E and 4.10s doing about 75. I'm sure it would be better with 3.73s or 3.42, but who cares.

On the other hand my 97 CCSB on 35s w/ a 6" lift that weighs in at 7500lbs is AVERAGING 16.6 mpg (high of 20.4) over the last 16000 miles. Oh yeah, it has a cummins in it . I bet a 2wd 67-72 would get close to 30mpg with a 12V cummins in it (and probably over 30mpg with a 4bt).

[67ChevyRedneck]

The aerodynamics of a BRICK factor in as well. My truck weighs in around 3,900lbs with the 350/700R/3.73, A/C, etc. When going 70mph, if I let off on the gas I feel the truck quickly decelerate. In my 2000 Z71 which weighs like 5,600 lbs, has a 5.3/4L60/3.73, the "slow down" is much much less noticeable when I let off the gas at the same speeds. The whole extra weight argument becomes a wash when you factor in the crappy aerodynamics of these trucks. So yes, if modern trucks were back down to weighing 3,700 lbs, yeah, with their aerodynamics they would get much better fuel mileage! Even most midsize family sedans weigh 3800-4200+ lbs now a days.

We've also had quite a few "what does your truck weigh" threads over the years and most short beds come in around 3,700-4,000 lbs

[quick60]

Im running an L6 250 so kinda comparing apples and oranges but I saw a dramatic increase in fuel mileage and performance by tuning with a vaccum gauge. Adjusted the timing for best vaccum and backed off just a little then adjusted the carb mixture screw for best vaccum. Also added greased lightning to the oil. I know it sounds goofy but I think that made a big difference as well. The engine drivetrain definately quieted down and seemed to run much better. There is a forum member who owns a parts biz that has a page on their web site on how to tune with a vaccum gauge but I cant remember who it is. He also suggests driving with a temporary vaccum gauge set up in view to show you how much your lead foot affects mileage.

Id be interested if the OP just added the greased lightning to see if there is any improvement at all.

[i82much]

Originally Posted by 67ChevyRedneck

The aerodynamics of a BRICK factor in as well. My truck weighs in around 3,900lbs with the 350/700R/3.73, A/C, etc. When going 70mph, if I let off on the gas I feel the truck quickly decelerate. In my 2000 Z71 which weighs like 5,600 lbs, has a 5.3/4L60/3.73, the "slow down" is much much less noticeable when I let off the gas at the same speeds. The whole extra weight argument becomes a wash when you factor in the crappy aerodynamics of these trucks. So yes, if modern trucks were back down to weighing 3,700 lbs, yeah, with their aerodynamics they would get much better fuel mileage! Even most midsize family sedans weigh 3800-4200+ lbs now a days.

We've also had quite a few "what does your truck weigh" threads over the years and most short beds come in around 3,700-4,000 lbs

Weight is a bigger issue for stop and go, drag coefficient is a bigger issue for highway.

[67ChevyRedneck]

Originally Posted by i82much

Weight is a bigger issue for stop and go, drag coefficient is a bigger issue for highway.

Very true. My 67 averages 12 around town and the Silverado 14. I attribute the differences to the carb and my right foot

[i82much]

Originally Posted by 67ChevyRedneck

Very true. My 67 averages 12 around town and the Silverado 14. I attribute the differences to the carb and my right foot

Ya gotta smack 'em around every now and again or you may as well just drive a Prius!

[Dunenutt]

http://www.network54.com/Forum/21565...+Fan+Dyno+Test

Found it...

[i82much]

Originally Posted by Dunenutt

http://www.network54.com/Forum/21565...+Fan+Dyno+Test

Found it...

That's a good test, and certainly seems to show that fans can draw substantial amounts of power. On the other hand, those tests are measuring how much the fan draws on full-throttle runs through the RPM band. I am thinking at 2500 RPM or so the numbers are quite a bit smaller (at least the direct driven fans without a clutch, not sure how effective the clutches are at slowing the fan at higher engine RPM).

[DreamRyder1963]

Originally Posted by Dunenutt

http://www.network54.com/Forum/21565...+Fan+Dyno+Test

Found it...

That's an interesting article. It would be nice to gain 10% from a simple fan swap.

[chevy72blu]

I get 22-23 highway with an LS1/4l60E/3.73 on a 29" tire. Truck weighs right at 4k lbs with a full tank and my fat butt in it.

More important than anything else is how you drive it. Its not just keeping your foot out of it, but coasting to redlights/timing them to minimize acceleration, leaving intersections slowly, etc, etc. My wifes new car has a fancy trip computer with instant/average MPG and I've learned a lot from keeping my eye on it while driving. "Normal" would put me around 24-25 city while really upping the grandma factor gets me up to 33-34, more than the epa estimate for the vehicle.

[davepl]

Originally Posted by nightmare

I beg to differ with this. There have been studies done that show all the "technology and safety" that goes into the newer cars also decrease fuel mileage. Besides, vehicles have gotten bigger as time has progressed.

Had vehicles stayed the same size as they did back in the late 60's and early 70's, but the engine technology still progressed, we would probably be getting 25-30mpg routinely.

I can't agree there - the technology has not hurt mileage, it's only improved it. I'm not sure, other than carrying the weight of wires and chips, which is silly, how it could be otherwise.

Now on the weight part I agree. My Range Rover Autobiography weighs a good 2000 more pounds than my Longhorn (about 6800 vs 4800). And the hilarious part is all the weight savings - aluminum bodied, aluminum engined, titanium who knows what ... just to keep it at 6800!

Minimum base curb weight I could find for an F-150 is 4685, which isn't all that bad. And you'll max it out at 23mpg highway.

After all, at some point it requires a certain amount of fuel to move a a pound of truck against air drag.