Increased MPG for carbs?
 

Right now I have an '81 C10 single cab, long bed, two-wheel drive model pickup. I'm wanting/needing better gas mileage. I have a 350/350 combo right now, and would like to keep it that way, but if I can't really get any better mpg out of it, I suppose I'll have to swap it with an EFI motor QQ lol

My question is, how can I increase the gas mileage more?

Currently, I'm fixing the previous owner's neglect and putting life back into this behemoth. When I got it, I was probably getting about 6-10 mpg city. I never got to really do the whole calculating thing because I was always stretching the last dollars of my paycheck when I actually HAD work. Now though, I feel like I'm getting better mpg. I've put on an Edlebrock performance intake manifold, a Street Avengers series Edlebrock 600 cfm carb, Edlebrock breather kit and air filter, and have replaced all of the exhaust line, pardon the manifolds (which are next when I get income again). I have a 3" exhaust true dual exhaust line with Thrush Welded mufflers on each line minus cats.

I'm going to be honest and say that I literally have no mechanical incline, besides changing tires, batteries, headlights, and oil. That's only because I worked at Walmart's TLE section for two years. I love cars, and have a lot of stats memorized about them, but you hand me a wrench and I'll stare at you dumbfounded. I won't try to claim that I know anything that I don't, especially with this being the case.

I've been told that a bigger pipe, pardon the massive ones unless it's diesel, will increase both power and fuel mileage. I was also told an X-pipe would help, but not until I had my exhaust already put on. Does it? If so, should I do it when I get the headers put on?

I was also planning on lowering my truck a little bit to get the "bruiser cruiser" look, and to increase fuel mileage. I've been told that a lower stance will help aerodynamically to decrease drag, increasing mileage.

Also, I was planning on putting aftermarket wheels onto my truck (no bigger than 20s, and most likely 18s). I know that these won't effect gas mileage, but I heard that if I changed the wheels I would have to mess with the gearing of the truck since it was built and tested with the 15s. Is this true?

However, I was also wanting more power as well on top of gas mileage, but as of now, those roles have reversed. I've been told that you have to sacrifice one to have the other, but I don't want to believe that. I just want a nice blend of each.

I also just read about modifying the carb to increase gas mileage. However most of those people have "vanished". The way one man described it was that it ran on gas vapors instead of actual raw fuel and that it was more potent that way. Which, to the untrained such as myself, sounds like power while also boosting mpg.

I also know that on TBI and EFI that if you put a cold-air intake on the vehicle, it will give you some power and also increase gas mileage. Is it possible on a carburetor motor? And if so, will it have the same effects?

Lastly, I know that diesels and small tuner engines use turbos to boost power and I've heard that it WILL increase gas mileage and that it WON'T. So which is it? Does anyone know?

If anyone or a few people can help give me some insight to these questions or even suggest other methods (besides converting to CNG as it costs too much for me at the time), I would be thrilled to read them and think them over.

Thanks a bunch.

Re: Increased MPG for carbs?
 

The first step that I would recommend is to calculate a baseline of your current mileage and you ideal mpg goal. There have been plenty of recent threads on how to increase MPG. Just keep in mind that without an overdrive transmission or running a diesel engine, it's going to be hard to get much more than 15 ~ 17 mpgs.

It sounds like you have your truck already setup very nicely. IMHO the 3" pipes are just about right, I would have done 2 1/2" pipes. The street avenger carb is supposed to have an extra spring to delay the control of the secondaries (for an additional fuel savings of around 5%). Are you running the stock cam shaft? I would recommend a towing cam (which would be a little bit more performance orientated). Headers would help with improving the MPGs but only by 1 or 2 MPGs.

Honestly, (as long as the engine is running properly) a lot of if depends on how you drive the truck.

BTW I am getting around 12 mpg with a 454 (recent tune up) and 4 speed granny. I drive like a man twice my age and keep it under 65 MPH; If I drove like other drivers my age it would be closer to 8 MPGs.

Good luck

Re: Increased MPG for carbs?
 

I feel like there's a way to get more than 15-16 mpg. That carb tweak I mentioned, when the guy learned about it from the guy that told him how to do it, told the writer he was getting 150 mpg. I'm just looking to get in the 20-30 mpg range. And I truly believe this is possible, as other stories have surfaced similar to the carb tweak one. Students at Kansas University bought a wrecked F1 car and used the motor in it that was pushing around 890 hp? I think that's what they're pushing, anyways, they took that motor, built their own frame, and crafted a body around it, and it was getting 115 mpg. I feel like I can get my goals with builds like this happening, and still get a decent 300-500 hp.

However, I also have been told what you told me a few times. So I dunno. If I can make it, I can, if I hit what everyone else is hitting, then I'll just have to accept that, haha. Most likely at that point, I'll just switch to EFI and try to increase gas mileage from that motor.

Thank you for your input though. :D

Re: Increased MPG for carbs?
 

I think that alot of it has to due to the lack of not having an overdrive trans. Also the efficiency of gas has actually decreased with the new blended fuel.

Even the top of the line new model gas trucks are only getting low to mid 20's MPG (with v6 engines). Diesel trucks get much better mileage and are more efficient with their fuel.

Check out this PM article:

http://www.popularmechanics.com/cars...nt-than-diesel

Re: Increased MPG for carbs?
 

I'm sorry to burst your bubble, but you will never get 20+ mpg in one of these trucks unless you go LSx with EFI or 6.2L diesel. You MIGHT crack the low 20's then, but that's it. The story about getting 150mpg? 100% complete and total BS. Pure and simple. Never going to happen.

The 115mpg chassis with 890HP? Sure, if you have a custom body with a super low co-efficient of drag and run the motor in it's most efficient range around a track without using the throttle after initial acceleration. But in a 30+ year old truck? May as well drive a barn door down the road.

I'm sorry, but your hopes and optimisms are just completely outside the scope of reality. With some tweaking and fine tuning, proper gearing, and a healthy engine, you MIGHT be able to pull down 17-18mpg on the highway, but your city mileage would suffer. Then, at that point, you have to ask yourself...how much money did I just spend to get 2-3mpg more out of this motor? Many times, people get so caught up in the mileage numbers, that they forget about cost and return on investment. If you spend $3000 to increase your gas mileage by 2mpg...It's going to take a looooong time to break even.

Let's break it down:

12,000 miles a year
15mpg
$3.75/gallon
That means you'll be spending $3000/yr on fuel ((12,000mi/15mpg )* 3.75)


12,000 miles a year
17mpg
$3.75/gallon
That means you'll be spending $2647/yr on fuel ((12,000mi/15mpg )* 3.75)

You'll save, on average, $353/yr. But you spent $3000 to gain those few mpgs...

It will take 8.5 YEARS to break even on your investment. It would be better to just accept your current mileage, or whatever you can gain from simple tweaks, and just run with it.

Re: Increased MPG for carbs?
 

:ito:

Re: Increased MPG for carbs?
 

My grandpa's doesn't. His is a 2004 F-250 King Ranch and he's only getting 11.3 or 11.8.

He had a cold air intake on there and it gave him 2 more miles per gallon, but his warranty wouldn't let him have it on there or it would void it. However, he also forgot to keep it, so someone got a free cold air kit, haha. I've thought about ditching my 350 turbo for another tranny. If I did that, I'd like to get a 5 or 6 speed. Do you know of any that can mount up to an old motor like mine? Are there adapter plates for that? Or would I just have to replace the motor if I wanted a tranny like that?

Re: Increased MPG for carbs?
 

My grandpa's doesn't. His is a 2004 F-250 King Ranch and he's only getting 11.3 or 11.8.

He had a cold air intake on there and it gave him 2 more miles per gallon, but his warranty wouldn't let him have it on there or it would void it. However, he also forgot to keep it, so someone got a free cold air kit, haha. I've thought about ditching my 350 turbo for another tranny. If I did that, I'd like to get a 5 or 6 speed. Do you know of any that can mount up to an old motor like mine? Are there adapter plates for that? Or would I just have to replace the motor if I wanted a tranny like that?

Re: Increased MPG for carbs?
 

The 350 is a popular engine and has been around so you have a decent tranny selection. What gears you got in your rearend?

Re: Increased MPG for carbs?
 

in the city with my 86 i get 14-15 but that is where i live not really city. same as my dads 97 ram 2500 on the highway tho it is diff i get a constant 21 or better at speed with no overdrive and mine weighs in at 5200lbs and stock hight with bfg at's on it.after 80 tho it drops fast. my motor is a crate 350 with stock q jet. have been told that the air dams help alot. as far as diesel there are guys in the mid to uper 20's with isb's and 4bt's. 6.2 that i have got me 21 at 75 on FLAT land hills killed it

Re: Increased MPG for carbs?
 

Think about it, your driving a giant barn on wheels, well about the same shape. You also do not have computer sensors and gadgets to regulate anything, most carbs act like a water hose with gasoline for the engine. Unless you go with a late model computer controlled engine I doubt you will make it to the high teens. The most I have read on here about mpg's was 17-18, but I think they had an overdrive trans.

Good luck though, I'm trying to squeeze every bit I can outta mine.

Re: Increased MPG for carbs?
 

If a 6.0 PSD is still running after 50,000 miles is a miracle;)

Re: Increased MPG for carbs?
 

In my Malibu and if I drive nice, I can pull 20-22mpg with a smallblock.

My K20 with the 454? 11-12mpg with 4.10s and 35s.

Re: Increased MPG for carbs?
 

Just so you know a f1 car avgs 3.1mpg some one is pulling your leg big time.Take a look at http://www.popularmechanics.com/cars...-finalists-won Its 840lbs with 40hp that's what a real 100mpg+ car is.

Re: Increased MPG for carbs?
 

Adding a turbo to a diesel engine usually decreases solo fuel economy but helps with heavy pulling fuel economy since the engine doesn't have to struggle so much and blow black smoke.

Re: Increased MPG for carbs?
 

Ok, so I finally found it, and it turns out they used a carbon-fiber F1 chassis and an electric driving system. It hits 300 mpg though, which is still pretty cool.

And so what about my bubble? I'm still optimistic that there is something out there that can break 18mpg for us "barn doors".

On top of that, I also feel like the stories of getting those huge numbers off of modding the carb are true, since I've heard them from a few places even when I was growing up. My grandpa even knew a guy that did the conversion himself and saw similar figures, and did so for anyone that paid him for his time to do so, but he lost contact with him a couple decades ago it seems.

The whole idea is plausible. I mean, the entire "theory" is that it uses fumes, which are much more potent and easier to consume than raw fuel. If you've ever lit alcohol on fire, it's the same thing. The fumes are so flammable that the liquid never catches on fire. The flame actually just causes the alcohol to evaporate and burn above it.

Think of it another way. You hear of houses being soaked in gasoline and lit on fire. What happens? It burns down. Then you hear about a gas leak in another house. What happens when a flame is introduced? A cinema worthy boom.

Besides, if it doesn't work, then I'll be where I'll be. If it does, then huzzah! I've done it.

Re: Increased MPG for carbs?
 

Hurray for the Powerjoke! lol

Re: Increased MPG for carbs?
 

There is something that can break 18 mpgs in these. An ls swap and a double overdrive. Not much short of that though... A turbo can help improve economy, but only if you drive it that way. Your best bet is to tune the carb properly, keep your fluids clean and full, check your tire pressure, grease EVERYTHING, and drive it like your grandmother. And I'm sorry to say, but there is no magical carb tune thing that turns gas into fumes and nets over 100 mpgs. If there was every car manufacturer in the world would be doing it stock.

On a side note my fiance's Honda Civic Hybrid gets over 40 mpg. You could always spend all the money you'd put into an EFI setup into buying a more efficient car...

Re: Increased MPG for carbs?
 

Well it is possible to hit 18 mpg on a carbed truck. My 1972 GMC, 1/2 ton, 4x4, 350 cu in, did even better than that and that was in the early 80's. Here's the formula.

1. 3.08 gears
2. SM465 4 speed manual
3. P235/75/15 tires
4. SP2P Edelbrock intake manifold (small diameter intake runners)
5. Rhodes lifters
6. High lift / short duration cam
7. Quadrajet carb (leaned out for best fuel economy)
8. Carb spacer
9. Timing advanced
10. Water Injection
11. 55 mph

For even better fuel economy, I would use Vortec heads so I could run more compression and more timing advance. The Vortec heads should be good for an additional 1-2 mpg. Also, for highway driving, 2.73 gears would even be better.

Re: Increased MPG for carbs?
 

For the 1990 Suburban listed in my signature, I'm getting on average mid 20's with that setup. At the price of fuel these days, it has already paid itself off.

But my 1982 Suburban 6.2L diesel (1/2 ton, 2x4, 3.08, 700R4) does even a little better. With some help from some exhaust headers, fuel economy is in the upper 20's. I even got 31 mpg one time on a long trip being very careful with the gas pedal.

Re: Increased MPG for carbs?
 

Unrelated to the main post but Edahall: I always considered going with a GV unit or a 6 speed to gain some more drivability, but I never considered both. Whats the OD gear ratio on that thing?!

Re: Increased MPG for carbs?
 

Gear Vendors OD has a ratio of 0.78. With my 6 speed manual and Gear Vendors combined, the final ratio comes out to 0.546. This puts the engine RPM at 1251 at 60 mph.

Re: Increased MPG for carbs?
 

Gotcha, I think for the money I'll do a t-56 magnum for the 0.50 ratio, but that is a rock solid setup for sure! Wish they did a GV for the T-56...

Re: Increased MPG for carbs?
 

Don't know if that would hold up to a Cummins putting out 1000+ ft lbs of torque at 1700 rpm's though.

Re: Increased MPG for carbs?
 

I know what you have in your truck, I said I would do a T-56. I definitely wouldn't put one behind a well built diesel, but I only have a 350. I just know that they make GV units that match up to a lot of the GM 4 speeds, but the ratio's for OD aren't what I'd like to get. I'd never looked into anything more than a 4 speed with it though. If your 6 is right around the same then it isn't worth it to me, but again, mine's only a 350.

Re: Increased MPG for carbs?
 

Just so you know, that's how every carb on the planet works. You don't just pump liquid fuel into the cylinders, the carb atomizes the liquid fuel (turns it into "fumes") by using a a venturi and engine vacuum.

Re: Increased MPG for carbs?
 

just find a 700r4. all youll need to do is move your trans crossmember back about an inch shorten the drive shaft and put the tv cable on.

its a lot cheaper then a gv unit

ive built my engine light and full roller just to save fuel. i got fuel injection and a 5 speed headers, h pipe, i went from 4.10 to 3.73, and i have 4wd
i get 20mpg highway easy even with a 1 ton the old lock out style front ends they work wonders

all i really wonted to do was go on the highway and i wonted 4wd, i was able to do that with just the transmission and adapter. i was only getting 12mpg ... i only got 1 tank and long trips changing elivation is not too easy to do with a carb so i put efi on it and the gear change was just a why not.

Re: Increased MPG for carbs?
 

You may as well take that statement right out of the conversation, the Fords have awful fuel economy. I worked as a fleet manager for a while for a small shipping company , the fords use substantially more fuel that the dodges the duramax is in the middle between the two

Re: Increased MPG for carbs?
 

I have a neighbour who regularly drives from western ontario to Northern Alberta with the same set up you listed ( 6.2 700r4 3.08 2wd) and he gets the same 29-32 range on his trips. He is 70+ and drives like he is 90+ , but he gets amazing economy.
Nice suburban too.

Re: Increased MPG for carbs?
 

To start with, I'd prefer a quadrajet over that Edelbrock. Edelbrocks require their own calibration kits for any tuning. Speaking of which, the only real way to dial in any carb is with a wideband, otherwise you are shooting in the dark. That coupled with a correctly curved distributor will yield some gains in MPG. I shoot for a leaner 15.0 AFR for very light throttle and idle conditions, while still maintaining a safe 12.8 AFR under heavy load. And I generally go for about 16 initial timing with 20 degrees of centrifical built in for a total of 36,,,should be a good starting point for most engines give or take a few degrees. Then dial in about 12-14 degrees of vacuum advance with an adjustable unit, and hook that to manifold vacuum.

Done this way will give you the best all around performance and fuel economy you could expect from any engine. From there it's all basic stuff. Free flowing exhaust with an X or H-pipe, long tube headers, a good dual plane intake will all help.

Then attack all the HP dragging rotational weight. Dual electric fans will free up some HP and mpg over a mechanical fan, aluminum driveshaft is easier to turn. Lightweight wheel and tire package is easier to turn, then pay attention to the size and the tread pattern as these can affect mpg as well. You could go as far as lightweight viscosity oils throughout. A good working fresh air intake system is free HP. Basically anything you can do to make life for the engine easier will generally return you with MPG gains. You can really get nit picky here, but it all adds up. There is much more to do as well.

I get a respectable 14 mpg out of my 79 1 ton with a 502/400 turbo and 3.73 gears in a truck that weighs 5500 lbs. with some of these tricks mentioned. It cruises nicely at 65 mph at 26-2700 rpms. That's through a power robbing 400 turbo and that huge 14 bolt full floater.
I am doing a custom aluminum radiator with dual electric fans, a gear vendor overdrive unit to drop cruise rpm 3-400, and will eventually go to a lighter wheel/tire package. Currently the 16.5's weigh 65 lbs. each with E load range tires on it :lol: I should gain an easy 2-4 mpg with all these changes and put the truck nearly at what some of the new trucks get for mileage. Respectable for a 500 cube gas engine with a carb ;)

My 72 4x4 blazer with a 6.0/4L60 swap gets 22 mpg with 3.73 gears and 33" tires, it weighs 4600 lbs. I run a lightweight wheel, and kept the tire width to 10.5", and a mild tread pattern (BFG all terrains) all help the rotational mass and rolling resistance. I also did dual electric fans on this swap, and I have a sharp custom tune in it using HPtuners and a wideband. That's the sweet part with this EFI, you can fine tune the fuel tables as well as a few other little tricks. Alot of my gas mileage with this rig is in the tune.

You can get upper teens in these old trucks with a carbed 350 using alot of these tricks and a sharp tune, with the right gearing and tire size. But it's going to cost money to do it. Whether it's worthwhile is up to you. That depends on what you plan with the truck, and how long you are going to keep it.

Re: Increased MPG for carbs?
 

Lots of good ideas here. I have learned over my 40 some years that if you start by optimizing what is there first is a good place to start. I am a huge fan of Taylor wires! For these trucks, Spiro Pro wires are the way to go. VERY low resistance and no radio noise (and cool colors if that is what you need). I would NOT do a cool air intake, that will hurt mileage. I would actually let the motor take in the warmer air from the motor. Open elements are cool if it doesn't rain. K&N or like that is great for flow.

Not a fan of carb spacers. A good dual plane intake, either stock or raised is fine. Go with Performance Distributor module and coil! This is a must. But you better have the Taylor wires I mentioned. Stockers will explode!. Gap plugs at about .050-.060, really! The ign. upgrade is good for a few mpg. I do this on all the trucks/cars I have had. Going to Taylor wires on my 2012 Silverado as soon as the motor is broken in. My 2005 Silverado 1/2 T got 27.2 mpg with a 5.3. That is 65mph on the hwy.

Carb is up to you. Just read your plugs, this is huge! Very little color on the insulator is what you want, lighter than cardboard. I have run Holley a lot over the years, all sizes and configs. The one that had the best milaeage was the 4010 body style that they dropped. BUT! Summit picked up the casting rights. Take a look. the whole top comes off. No gas spill changing jets. They have annular discharge boosters rather than the down leg or "dog" leg boosters (i.e. more efficient). The regual Holley guts work except the top body gasket. No other gaskets are below the fuel level. Cool huh?

On the dist, I always ran the manifold vac. and not ported. On a 350, I run about 34-36* of total advance all in by 3500. Depends on what your motor/cam likes.

Was playing with converters, a 2500 stall works great on the street. Get a Gil Younger valve body kit for the 350TH. They run cooler, no slip, last for ever. Oh ya, add a cooler always.

this is getting long... Have heard about running synthetic lube in the rear end, just not made up my mind there.

the bottom line? Drive like an old man, take your time, keep the right foot light and gradual. If you need to be there 30 min. ago, you should have left earlier.

Keep up the great site!! I have open ears, let me know what works for you, please!!

Re: Increased MPG for carbs?
 

Thanks for all these ideas guys! It's interesting to read all the different styles to get to the end result. However, I'm thinking about saving up for either an EFI engine swap, or buying a custom built 383 Stoker from Unlimited Performance. They're priced at $8,200, and are built to exactly what I ask them to build it for. And it comes with 380 hp and 440+ ft-lbs. of torque. :D I might even see if they can take that and EFI it as well.

One day, I'll also find something to cram one of their 572s in. :D $19,200 built from scratch and has 790 hp. Pretty sure that'll be my midlife crisis, haha.

Re: Increased MPG for carbs?
 

I built the 383 stroker, for the money, I wasn't that impressed. Seemed like a lot of work for very little. In what little I have done, the heads are everything! The cam, well, duh, sure. It really depends on where you want the torque to come in and the $$$ too.

Guess I am to old school. I like my Holleys. I can tune them to do whatever I want. I like the throttle snap that I can get that EFI can't. Seems like there is just a little delay on the efi stuff. Guess I have tinkeritis too. Think it is a guy thing, really.

Had fun with the emissions test once too(off topic). They said my 52 5 window p.u. with a 410 wouldn't pass the smog test. Legally, I don't have to. I have to meet EPA emisions that were required in 1952. In Missouri, we don't have smog tests anyway, this guy was being a jerk. I went home, switched carburetors, put a barrel of alcohol in the bed. Since I ran a racing fuel business, it was not a big deal. Went back, told him to "sniff this". He plugged in his stuff, I started the truck and "gassed everyone in the building! The were all running out, gasping, wiping their eyes. I laughed my head off. I passed the test!! They told me to take it home and not come back. One officer asked me to launch it hard once. Told him I didn't want the ticket. He threw his badge in the car and told me to have at it. I pulled out on the street, dumped the clutch at about 4500 and picked up the front end and carried it through 2nd gear and let it down. The officers all just waved at me.

This little stunt of just 60 miles round trip cost me a barrel of alcohol ($165) but they learned their lesson. It was a blast too seeing everyone scatter!! ;)

Have fun, enjoy the life and the pursuit.

d

Re: Increased MPG for carbs?
 

A simple a/f meter and some good tinkering on a carb will net the same mileage with a carb vs efi

Also 9k for a 383 crate engine??? That sh!t better be putting out 600hp. 380hp and 440 tq can be put down by a vortec 350 with a 268 cam and headers. That's about 2k
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Re: Increased MPG for carbs?
 

Wow. Those guys are WAY overpriced.

Re: Increased MPG for carbs?
 

You guys are thinking too hard...hypermilling!!! Go to about 55mph, turn of engine coast to stop light, turn engine back on :)

Re: Increased MPG for carbs?
 

Your right, a good friend of mine who is a gm asap tech, one of the old school guys who worked at a dealer says that a carb properly set up can out perform a efi set up, his vehicles always have been amazing with holleys and quadrajets .
He does say the quad is a better more fuel efficient design.

Re: Increased MPG for carbs?
 

The Quadrajet will return better mpg for a few reasons. The front primaries are smaller, a very efficient booster design atomizes the fuel, and the metering rods offer very fine fuel metering.

Without a wideband AFR to do your tuning with however,,,you are basically shooting in the dark. With the right lean part throttle adjustments made using a wideband, you can get great mileage out of most any carb,,,some are more involved to deal with, but the end results are similar.

EFI shoots for a target 14.7 AFR all the time unless you are in PE mode (power enrichment).

You can shoot for this same AFR using your wideband and in some cases even a little leaner doesn't hurt anything on light throttle cruise, light load conditions. Some tuners have gone as far as 15.0-15.3 AFR for light cruise applications and pick up some MPG. I've flurted with 15.0 on some of mine, and it's been fine for years. On my 502 pickup however I prefer to keep that one slightly on the rich side (14.2-14.4) at part throttle because I use it for towing heavy loads. At low vacuum conditions (half throttle or more) when towing up hill or pulling away from a stop, the power valve opens and quickly richens it to the low 13 AFR range, and full throttle is at 12.7 AFR, like I said, slightly rich but I feel it's better protected from detonation this way while towing.

The problem now though is ethanol in the gas. The more ethanol in the fuel the richer the fuel mixture has to be to make the same power. Even 10% will change the AFR .3-.4 tenths so there is a fine line there,,,and then it gets more involved depending on where you fuel up the car. Not every station carries the same amount of ethanol. I've seen them carry as much as 17% using a little ethanol test kit. So gas mileage, (and you tune) will change from one fillup to the next.

As far as a carb working better than an EFI is up for debate. The advantage EFI has here that I find tuning my LS engines, is the very fine detail fuel adjustments that I can make in the fuel table cell blocks which creates an entire graph or fuel curve. I can make it do what ever I wish and get some pretty darn good fuel mileage out of it with a key stroke. The adjustments are infinate. On a carb there can be certain areas that you'll have to fudge and live with where the AFR dips or jumps around,,,unless you run a very expensive carb that has adjustable air bleeds, adjustable power valve circuits etc....and it gets pretty involved.

However it has been shown on the dyno with the same engine that a carb still makes more HP and torque by a very slight margin.

They both have good and bad points.

Re: Increased MPG for carbs?
 

In all fairness he was comparing late 1980's early 1990's fuel injection, Throttle body to carbs not the more sophisticated systems that we have today.

Re: Increased MPG for carbs?
 

MPG with a Quadrajet is better than Holley because of the tiny primaries and HUGE secondaries vs the Holley's all 4 bores being equal sized. Keep those secondaries closed on a Quad and you can pull more MPG out of it vs throttle body for much the same reason (TB has two large bores to flow the same air WOT as a Quad).