5.7 vortec mpg

[evilunclegrimace]

All true, just seems like a large jump in mileage especially considering everybody else's experience as well. I was hoping you had some profound knowledge we didn't. Turns out I just need to stop driving like an idiot. I was really hoping otherwise, I like driving like an idiot [emoji3]

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The skinny pedal is a lot of fun but it does come at a price. My SCSB 5.7 w 3.73 gears and 245/65R75 tires pulls 17.2 MPG's at 75 MPH on a 2 hour drive from Erie to New York state through the hills at Ellicottville.
The wife's '92 RCLB 5.7 with 243 gears and 265/75R16's only pulls around 14 MPG's in the city.

 

[L31MaxExpress]

Hmmm... I do run taller tires (33") and most of my miles are city, but I'm never in stop and go traffic. Is the added weight offset by aerodynamics with the suburban? So many people reporting mileage in the same ballpark, then yours comes in 33% higher, what are we doing wrong?

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Mine has always gotten alot better than 15.8 on the highway. My worst tank going to Ohio a few years ago and back was just under 17. My best tank was just under 19. Had the tuned 0411, 395' marine cam, marine intake, thorley tri-ys, exhaust, 4L85E, 9.5" 14-bolt with 3.73s and 31.5" tall 20s. The stock 5.7/4L60E/3.42 on P235/75R15s was consistently over 18 mpg highway. Running anywhere between 75 and 90 mph. I am sure being 2wd helps when it comes to driveline losses and drag though. When my 2nd 4L60E was starting to die, it would not lock the converter. I drove it for months in 3rd gear on the highway. It still got 15-16 mpg running along at 3,000+ rpm in 3rd with the converter unlocked.

 

[Supercharged111]

Any chance you'd be willing to share anything other than "you're wrong"? It's not exactly constructive.

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Yes, data logs which are on my laptop at home (I am not). Fast covered it with MAP drop, my observations were very similar and this was before I deleted the lip.

 

[Awest623]

The throttle body is the narrowest point in the intake system, stands to reason an additional half inch or so of diameter would increase air flow through the system. Whether or not the fuel system has enough overhead to take advantage of that available airflow remains to be seen, but the anecdotal evidence of the two users with experience is enough for me to take a chance with it. Especially with my future plans of putting in a 383, and the relative low cost of the part.

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The throttle body wouldn't make a difference because it's not the restriction. The stock vortec intake manifold is the restriction. You want more flow? Do a manifold swap, otherwise the throttle body ain't gonna make a damn difference.

 

[Hobie]

The throttle body wouldn't make a difference because it's not the restriction. The stock vortec intake manifold is the restriction. You want more flow? Do a manifold swap, otherwise the throttle body ain't gonna make a damn difference.

But it does make a difference, not much, but it does. I recently made two trips (410 miles round trip) to the same location, both trips set cruise at 75mph, and the trip with the 350 throttle body made 18.8 mpg. (96 K1500 Z71 3.42 locker, 32" tires, with me, two bags of tools, and the usual things in the truck.)
Second trip was with the 454 throttle body and it averaged 19.9 mpg. Yes there could be tons of other factors, as it's not a huge long term data pool, but one huge thing to notice, is how much throttle it took to keep the truck at 75, 25-30% for the 350, and 12-18% for the 454, and as less throttle input was needed, I noticed there were a lot less downshifts during hill climbs. And due to the design of the 350 throttle body, there is a night and day difference between throttle response between the two. Yes it may not make any more power at WOT but it definately is a huge improvement in part throttle applications.

 

[CRF450R]

But it does make a difference, not much, but it does. I recently made two trips (410 miles round trip) to the same location, both trips set cruise at 75mph, and the trip with the 350 throttle body made 18.8 mpg. (96 K1500 Z71 3.42 locker, 32" tires, with me, two bags of tools, and the usual things in the truck.)
Second trip was with the 454 throttle body and it averaged 19.9 mpg. Yes there could be tons of other factors, as it's not a huge long term data pool, but one huge thing to notice, is how much throttle it took to keep the truck at 75, 25-30% for the 350, and 12-18% for the 454, and as less throttle input was needed, I noticed there were a lot less downshifts during hill climbs. And due to the design of the 350 throttle body, there is a night and day difference between throttle response between the two. Yes it may not make any more power at WOT but it definately is a huge improvement in part throttle applications.

I'm going to have to look at a 454 throttle body on eBay I didn't want to do a cold air intake but I started looking at them and I would say they are all hot air intakes untill I came across this Volant air intake it's tempting would it work with the 454 throttle body? And well I'm thinking of spending money what about shortie headers are they worth it I already have a full 3" dual exhaust no cats.

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[Hobie]

I'm going to have to look at a 454 throttle body on eBay I didn't want to do a cold air intake but I started looking at them and I would say they are all hot air intakes untill I came across this Volant air intake it's tempting would it work with the 454 throttle body? And well I'm thinking of spending money what about shortie headers are they worth it I already have a full 3" dual exhaust no cats.

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I'm really not 100% sure if it will or not, but if it fits on a 350 throttle body, I'm sure it will fit on a 454 throttle body. You can go through my write up on my truck thread, the 454 throttle body is just slightly wider in OD where the intake hat fits onto the throttle body, and the factory hat has to be "forcibly persuaded" onto it with light tapping from a wooden block or rubber mallet. Also I dont more reading after I performed the swap that some people have actually knocked the lip off of the 350 throttle blade, theoretically achieving the same result without having to buy another throttle body. But without a doubt, the final decision is yours rather you want to do it or not.

Also if you dont want to deal with tearing throttle bodies apart, and swapping them, I could perhaps put together plug and play throttle bodies if one were interested in this

And on the headers, in my opinion, I wouldnt go with shorties, but I would rather go with mid, or long tubes due to the gains throughout the powerband.
But shorties do have their place, especially if you already had an exhaust done, and want something bolt on, and shorties only seem to have an increase in low end torque, and I havent heard too many people claiming increased fuel economy with shorties, but mid or long tubes seem to have a consistent gain in fuel economy. But you'll have to have another custom exhaust put in once more

 

[CRF450R]

I'm really not 100% sure if it will or not, but if it fits on a 350 throttle body, I'm sure it will fit on a 454 throttle body. You can go through my write up on my truck thread, the 454 throttle body is just slightly wider in OD where the intake hat fits onto the throttle body, and the factory hat has to be "forcibly persuaded" onto it with light tapping from a wooden block or rubber mallet. Also I dont more reading after I performed the swap that some people have actually knocked the lip off of the 350 throttle blade, theoretically achieving the same result without having to buy another throttle body. But without a doubt, the final decision is yours rather you want to do it or not.

Also if you dont want to deal with tearing throttle bodies apart, and swapping them, I could perhaps put together plug and play throttle bodies if one were interested in this

And on the headers, in my opinion, I wouldnt go with shorties, but I would rather go with mid, or long tubes due to the gains throughout the powerband.
But shorties do have their place, especially if you already had an exhaust done, and want something bolt on, and shorties only seem to have an increase in low end torque, and I havent heard too many people claiming increased fuel economy with shorties, but mid or long tubes seem to have a consistent gain in fuel economy. But you'll have to have another custom exhaust put in once more

Well once the Truck is painted it's getting motocross decals down the bottom half of the truck plus some other advertising from buddy's truck accessories tire and Kawasaki dealer. It'll be basically used for advertising once it's painted so was just going for sound as I plan on buying a Tundra as my new daily driver it wouldn't be hitting drag strips

 

[df2x4]

All this talk about throttle bodies on the Vortec trucks... I have to throw in my two cents. As others have mentioned, the 350 throttle body itself is not a restriction on anything even close to a stock engine. Other users have proved this by data logging manifold pressure/vacuum. I would not go swapping a 454 throttle body onto a 350 unless you have serious engine modifications that require the extra CFM and plan on tuning the PCM accordingly. @Hobie, this is a complete guess but my gut feeling says the MPG improvement you saw after that swap was the PCM pulling fuel at part throttle. (Or more likely the fact that the 454 TB requires less throttle pedal to get an equivalent amount of air into the intake)

In regards to the lip on the throttle blade, it's there to smooth out throttle response. Removing it will gain you nothing as far as actual HP/TQ, it just makes the truck suck more air at low throttle levels. I know several people here have done that mod and enjoy it on V8 trucks, but my experience in my V6 truck was that it made my accelerator pedal feel like an on/off switch. I put a factory blade back in it with the lip still intact and I strongly prefer the more linear throttle response that gives me.

 

[Hobie]

I completely agree with you @df2x4 I dont believe that the throttle body alone will gain any HP/TQ numbers throughout the rev range at WOT, but at part throttle may be a difference? Again, I havent been able to look at any hard numbers, but it indeed improves throttle response. I always felt as if my truck was extremely sluggish for what it is, and it just feels much better, although I'd imagine no improvements in acceleration have happened.

Now all of this is just with my truck, I dont have any major modifications, just a very mild RV cam and 6" rods when the engine was over hauled.

And to the fuel economy, it may just be, and like I said I havent put enough miles to see if it actually did improve fuel economy, and I'll keep tracking things and see how it looks.