Need advice on what to do

I wouldnt say its an advantage to have a carb cause it can be tuned.  the Sniper for example can be tuned a lot more than a carb ever could be tuned.

You can set up a fuel map where AFR can vary from 12.3:1 rich for power down to 16.5:1 to 17.5:1 for cruise economy.

A carb you can tune it with in reason but you cant tune it to vary down to every 100 rpm like you can with fuel injection like a sniper for example.

Below is a fuel map that I did not even attempt to mess with but you can fine tune it so much better than a carb.  This is where something like the sniper shines is you can get it so precise that you will see a improvement in economy.  With a carb you may have to make concessions since you cant tune a carb down to such a small point.



Now if we are talking about OEM OBDI EFI then yeah a carb would be better as those systems dont have the adjustability and the tech is no longer there due to how old the system is at this point now.

I have a quick change kit for my Summit carb but never ordered the jets and the accelerator pump as that was lower on my purchase list.  But the more I thought about trial and error for making changes to fine tune it and how many times id have to take the carb apart to make changes, I started thinking about EFI.  The bright side with EFI is I can have it dyno tuned as well if I wanted to since a laptop can be used with it, dyno shops around here wont touch a carb unless you just want to see how much power your engine makes as far as tuning goes they wont touch a carb.  They really wont even touch OBD I systems either since it is obsolete and the tech to make the changes in the computer just isnt out there anymore.

Rusty, SD was all bank fired.
It wasn't until EECV and MAF that it went sequential port fuel injection.

It sounds like you are completely sold on the Holley Sniper EFI system, and that is fine.  But it also sounds like the main reason for replacing your carburetor with it is because you simply don't want to take the time to tune it.  That is also fine.  

The fact is, a carburetor is an analog device and it simply cannot self-tune or self-diagnose.  The main advantage to an EFI system is that it can.  In exchange, you pay a much higher price for it and get a whole mess of wiring, numerous sensors, and a computer to make that happen.

To be fair, manufacturers originally calibrated their carburetors (and ignition timing) for each specific application when they were new.  So they were set up pretty well when they left the factory.   As the years went by, vital carburetor parts often went missing (such as the choke, solepot, and air cleaner, for example) and they were often maladjusted to compensate for these missing pieces or to cover up a completely different problem.  Even worse, carburetors were unknowingly exchanged for a rebuilt unit with a different calibration than what it was originally designed for.  Or - in your case - the fuel blend changed, but your carburetor was calibrated to run on a much different mix.

I hope your aftermarket Holley EFI system works well for you. *PLEASE* don't be one of those people who replaces a very old, worn out, and out-of-tune carburetor they have simply lost interest in with a brand new EFI system, takes the time to install on their engine and goes through the programs required to properly set it up, and then claim it is so much better than a carburetor ever could be.  It takes TIME to properly set up a carburetor - just like it takes time to install and set up a complete EFI system.  All other things being equal, there isn't much difference between a well tuned and matched carbureted system and a properly functioning EFI system.

You really can't seem to accept that technology has left you in the dust.

But whether you choose to accept it or not, time moves on.
99% of things get better, not worse.
And titanic industries like semiconductors, automobiles and petroleum have been investing billions and billions of dollars to make these improvements while you've had your head buried in the sand.

No matter how many times you repeat your mantra, the past is not coming back, nor was it superior.
Are you down with the whole "Clean, beautiful coal!" garbage too?

Perhaps we should put electricity aside and go back to steam power and belching smokestacks spewing sulphur, mercury and arsenic.
So thick that it obscures the sun at midday, like Pittsburgh a century ago?

Because, you know, things just worked better then...

Or like the '60's & '70's when the air was yellow with automobile exhaust and your eyes burned in that acrid soup.

Modern EFI engines can actually have cleaner exhaust than the air they take in, in cities like Delhi or Bejing.

ArdWrknTrk wrote

You really can't seem to accept that technology has left you in the dust.

But whether you choose to accept it or not, time moves on.
99% of things get better, not worse.
And titanic industries like semiconductors, automobiles and petroleum have been investing billions and billions of dollars to make these improvements while you've had your head buried in the sand.

No matter how many times you repeat your mantra, the past is not coming back, nor was it superior.
Are you down with the whole "Clean, beautiful coal!" garbage too?

Perhaps we should put electricity aside and go back to steam power and belching smokestacks spewing sulphur, mercury and arsenic.
So thick that it obscures the sun at midday, like Pittsburgh a century ago?

Because, you know, things just worked better then...

Or like the '60's & '70's when the air was yellow with automobile exhaust and your eyes burned in that acrid soup.

Modern EFI engines can actually have cleaner exhaust than the air they take in, in cities like Delhi or Bejing.

That seems a bit uncalled for.

I am only comparing the power and fuel economy numbers of a properly tuned and matched carburetor with a properly functioning EFI system.  All other things being equal, there simply isn't that much difference.  

I agree with you in that modern engines do tend to burn a bit cleaner.  But that has less to do with EFI and more to do with better heads, camshafts, catalytic converters, etc. Even so, EFI is still going to be a bit cleaner for our environment because it can constantly self-tune.  That not only helps modern engines to last longer, but it also helps to keep our air cleaner if (and when) a problem arises, and every little bit helps.  

That being said, no one ever says they want a fuel injection system for "better emissions." Instead, I often hear things like "better cold starts" and "better performance" or "better economy" as reasons why from the companies who market them as well as the people who purchase them. Those are simply not valid reasons to replace a carburetor with a fuel injection system.  The truth is, if you replace your carburetor with an EFI system and you get "better cold starts" and "better performance" or a big increase in fuel economy, then something was not right with your carburetor.  

Perhaps I misrepresented myself in this discussion.  I do understand why carburetors were replaced with EFI. I do not think a carburetor is "superior" over EFI.  I have two other newer vehicles with EFI, and I would absolutely not replace either of them with a carburetor.

EFI takes all the fun of driving a car / truck with a carb from starting it when cold and needing to find what it takes to start. Do you pump 1, 1.5 or 2 times? Hold it a little bit or half way down after the pump?

Also going from carb to EFI for a few more MPG how long would it take for pay back?
Don't get me wrong I like EFI on the car & truck I have but they came with EFI.
Dave ----

I thought it might have been but I am not real up to date on EECIV based fuel injection that was a bit before my time as I didnt get training on computer systems on cars till after the 1995 OBD II switch over.

But I do know that group fired MPI EFI wasnt really much better than plain on TBI since they all fire at the same time just like on a TBI system.

Well the main reason is because my 306 build is going to be 4V regardless.  I have a Summit 600cfm 4V carb which is built by holley for Summit which is an upgraded variant of the holley carb based off the ford 4100 carb.

I was fully content with investing the time and doing carb, but with each installation of EFI and seeing how much better the sniper runs out of the box than a carb out of the box I started thinking to myself, for a truck I want to drive do I want to have to worry about making adjustments all the time like a lot of aftermarket carburetors tend to need which there is no guarentee that the Summit carb would be as bullet proof as the ford 2150 carb I would be replacing.  That is the thing that had me seriously weigh between the EFI and carb.  Can I be confident that once I invest the time to properly set up the carb would the carb run the same regardless just like my old 2150 that is being replaced or is it going to be like the holley 4150 I have on my 63 that needs the air/fuel mixture played with at least once a month.

For a truck that I plan to drive every day I dont want to spend more time under the hood making adjustments I rather be able to get in the truck and basically go.

That is what ultimately sold me on the sniper.

As far as the wiring, youd be suprised how little wiring there is with the sniper.  If you are doing it bare bones and not adding all the bells and whistles that you dont need for it to operate you only need to hook up five wires.  A battery hot, a battery ground, a rpm signal, a key hot, and run the blue fuel pump power wire.  In my case I would be actually hooking up seven total wires, a AC signal wire to provide idle up function with AC on and a AC trigger wire that on wot will trigger the relay it is attached to which will break the AC compressor circuit for an AC cut out.

This isnt like an EECIV or EECV type fuel injection system with 200 wires, the sniper has all the wires self contained with only a few hook ups needed for basic operation and then optional wires you can hook up for more features.

As far as my setup goes, the engine will be built, the system will be installed the basic tune will be setup then I am going to Crosby to a well known tuner and give him $200 for a dyno tune on the sniper.  Everyone I talk with he is the worlds best and has his custom tuning in cars in every country around the world.

Only reason I am losing the 2150 carb is a 2V carb is not going to be enough for a 306 build with a aftermarket roller truck cam with over .500" lift and AFR Renegade heads.  I need to switch to a 4V and that is where my concern with the carb comes in.

I dont find it fun when you hop in your car ready to go and your aftermarket carb is running bad and you have to play with the idle mixtures.  That is how my holley 4150 is on my 63.  That is what I started fearing with my Summit 600 cfm vac secondary which is built by Holley for summit.  I want to drive my truck not get it in to go some where and the thing starts running horrible and instead of getting in cranking the truck up and leaving I have to pop the hood and lean over the fender and make adjustments.

If I had 100% undeniable proof my summit carb wouldnt do that I would gladly stick with it.  But for me its not just the extra mpg, its the over all package ontop of me not having to go under the hood like on my Holley 4150 that needs the idle mixture played with at least once a month.

Now if your only reason for EFI is for fuel economy then yea I say dont do it cause its not worth it if you just want to improve fuel economy.  But if you want something that will adjust itself and doesnt require you to pop the hood every month or so to play with the idle mixtures like is common with aftermarket carbs like Holleys then I would suggest looking into it.

Me I have numerous reasons to go for it, the fuel economy improvement is just the cherry on top for me especially with a 16 gallon saddle tank.

I have a built up 306 myself, and like you, it originally had a Motorcraft 2150 carburetor that ran excellent.  When I rebuilt my engine and did the DSII conversion, I decided to go with a 4-barrel carburetor.  I got talked into a Holley carburetor, and I was never really that happy with it.  It ran okay, but it simply wasn't near as sharp and consistent as my original Motorcraft 2150 was.  And the electric choke was a real pain.  I never had starting issues with my Motorcraft 2150 like I had with that Holley.  I think that was the worse part for me.  Like with your '63, I felt like I was constantly having to fiddle with it.  I found out the hard way that an aftermarket Holley carburetor is a racing style universal  carburetor that is made to fit *any* engine - but it's up to the owner to make all the right adjustments in the right sequence to dial it in correctly.  

So I can understand the draw of a self-tuning EFI system.

One day after I fiddled with it (again), it started leaking at one of the fuel bowls. I got fed up with it and decided I needed to either replace it or find someone who knew what they were doing. I started researching stock Ford carburetors, hoping that there was a 4-barrel version of my reliable Motorcraft 2150.  I found exactly what I was looking for when I discovered the Autolite 4100.  Like the Motrocraft 2150, the Autolite 4100 had annular discharge boosters and a thermostatic choke - but it had two extra barrels!  I tracked down the right size and calibration, and with very little tuning, I was back in business.  I am happy to say my truck now runs better than ever with good power and even better fuel economy.  I have the simplicity and reliability of my original Motrocraft 2150 - but in a 4-barrel version that is the Autolite 4100.  Once I dialed it in, I haven't had to mess with it AT ALL in almost 10 years.  

This is my first and only vehicle with a carburetor, and I can honestly say that there is very little difference between driving it compared to my fuel injected vehicles.  

Unless you already purchased the Holley Sniper, I would strongly recommend you to consider an Autolite 4100.

I actually already have the sniper stealth.  I bought it last month along with a bunch of other stuff.

The Summit 600cfm I have is a Holley made carb but it is an upgraded version of the holley upgrade they did to the 4100 motorcraft.  I think it was a 4050 holley or something like that.

I just am not sure on if it will be just like other holley products, I was willing to give it a try how ever.  But I figured right now at the very least I can use it for my 351W on my 78 Mercury so I wouldnt be tossing the carb.  Or I could hold onto it in case the sniper stealth turns out to be more trouble than its worth.  But Ive installed 6 of them now with another two more on the burner to be installed in the next few weeks.  Never had a problem with them and we always sent them out with an out of the box wizard tune.  Customers were always happy with no complaints.

I did work on a '62 galaxy and I cant remember the other one it might have been a tbird but both of them had 4100 carbs on them, they were simple and tuned great when I rebuilt them.  Only draw back I found was locally rebuild kits wasnt something you could find locally and had to order it.  But like you said the Summit carb is just like the 4100 with the annular boosters and one piece design and could accept a quick change vacuum secondary kit from holley and used holley accelerator pump cams and the biggest difference from the old 4100 like you mention this is a straight electric choke.

Honestly I really did want to run this carb, but more I thought about it the more I started wondering about typical holley problems such as constantly making idle mixture adjustments over time.  I dont know if being based off the 4100 family of carbs would counter that or if it being updated by holley for summit if it would have the same issues.  I know lots of people love this carb and how responsive it is.  But I just never seen enough long term reviews on it.  I try to go by long term and if people have problems or not.

I put this Holley on my truck. https://www.holley.com/products/fuel_systems/carburetors/street_warrior/parts/0-80457S

I ordered 2 down on the jets I believe, for the altitude I’m at, 4100 feet. Once I got the choke where I liked it, took a few cold start mornings, it has been trouble free. It’s been on at least three years.

Those Snipers are cool, carbs are cool! Have fun with it!

My truck and fuel economy haven’t met yet!

LARIAT 85 wrote

I am running an Autolite 4100 on Lucille, and I can get about 18 mpg on the highway if I drive it right.  When I tuned it, I got better power and economy by going from the stock size 49 jets to 50 on the primaries and from the stock size 58 to 60 on the secondaries.

Rick,

My MPG is about the same (17.5), which makes sense given how closely matched our 5.0/302's are. Of course they're not identical...but I'd say based on our MPG that they perform very similarly at cruise RPM with similar weight swb trucks. I'd love to try one of those Summit M2008 500 CFM carbs, but I have my Holley working so nicely now I don't want to even touch anything.

I have an AFR gauge, so I know where my set-up is running (Usually around 14:1 on the highway, sometimes a little lower), and my plugs are clean as a whistle. When I take them out of the heads, they look like I just took them out of the box.

Comparisons are tough as lots of other things come into account...local climate and temps, road surface, fuel quality, etc. I know if I ditched my fat 275/60/15 tires for something more stock in size that I'd see an improvement in MPG.

Anyway, I know my carb can be tuned even finer, and my AFR numbers dialed in for even better mileage, but I'm too lazy to do it, and it's working so well where it is now I don't want to bother with it anyway.

I may swap in EFI someday, but as it stands now it is not on my radar.

From your description, it sounds as if your Holley is tuned very well to your truck.  I wouldn't touch it, either.  17.5 is very good fuel mileage for your truck.  I think to squeeze much more out of it would probably be at the expensive of power.

I think at this point the next step for both us in the fuel mileage department would be to get the appropriate gear ratio to better match our tires and more modern driving habits.  (My tires aren't as fat as yours, but they are taller.) These trucks were very conservatively geared off the rather small stock size tires and a national speed limit of 55 MPH.  I am fairly certain a lower (higher numerically) gear could increase both fuel economy and power for my truck.  

What is your cruising RPM at 55?

LARIAT 85 wrote

What is your cruising RPM at 55?

That's a good question. I'd have to check it to be sure, but I'd say around 1750 RPM. Wife and I put a couple hundred miles on the truck today but I was mostly running at almost 70 MPH, and at that speed my tach is reading only 2000 RPM. I have to drive a good 10 miles at 45-50 MPH to get from where I live to the highway, and if I recall correctly at that speed it's usually around 1500 RPM in 5th, or 2000 RPM in 4th. My truck is almost geared too tall, but I like the way it is.

Rembrant wrote

LARIAT 85 wrote

What is your cruising RPM at 55?

That's a good question. I'd have to check it to be sure, but I'd say around 1750 RPM. Wife and I put a couple hundred miles on the truck today but I was mostly running at almost 70 MPH, and at that speed my tach is reading only 2000 RPM. I have to drive a good 10 miles at 45-50 MPH to get from where I live to the highway, and if I recall correctly at that speed it's usually around 1500 RPM in 5th, or 2000 RPM in 4th. My truck is almost geared too tall, but I like the way it is.

1700 RPM @ 65 MPH is where I am at in over dive with a 2.75 rear gear.
Think 55 MPH is about 1500 RPM in over drive.
I am running 235 / 75 / R15 tires but I have a 300 straight six and it likes to pull at low RPM's.
I need to get the wife to do a ride along so I can track the MPH @ RPM in drive & over drive.
Dave ----

Have to also go by location cause 55mph highway speed is no longer the highway speedlimit country wide like it was at one time.  Here our highway speed limit ranges from 60 to 85 mph depending on where you are at.

I personally am setting my truck up to be around 70 - 75 mph in the cruise rpm range of the cam I have.

Cam I have, crane listed the cruise rpm to be 2,400 - 3,000 rpm.

With 31x10.50-15 BFG KO2 tires which are really 30 1/2" tall not 31" tall, which stock tires being 27.60" tall my 2.75:1 axle ratio currently is a 2.49:1.  If I run a 3.00:1 my ratio would be 2.71:1 which would be very close to the stock 2.75:1 ratio.  If I run a 3.25:1 my ratio would be 2.94:1 ratio which would give me a little more acceleration but will also raise my cruise rpm.

Now while I should shoot for 2.75:1 I am taking into consideration of transmission slippage, if I can get my transmission to have 3% to 5% slip then I can get by with a lower axle ratio for my goal otherwise I will have to go with a higher axle ratio.

Based off the calculations I have done I did 3% to 10% slip which seems to be the range for a C6 transmission but Hughes says their XTM is a tighter converter with less slip and many have told me a rebuilt C6 would be in the 3% to 5%.  The following is what I came up with accounting for ratio change based off tire size as well as slippage.

3% slip @ 75 mph : 2,724 rpm w/3.25:1 ; 2,515 rpm w/3.00:1 ; 2,305 rpm w/2.75
5% slip @ 75 mph : 2,782 rpm w/3.25:1 ; 2,568 rpm w/3.00:1 ; 2,354 rpm w/2.75
8% slip @ 75 mph : 2,873 rpm w/3.25:1 ; 2,682 rpm w/3.00:1 ; 2,431 rpm w/2.75
10% slip @ 75 mph : 2,936 rpm w/3.25:1 ; 2,710 rpm w/3.00:1 ; 2,485 rpm w/2.75

8% slip w/3.25:1 axle : 2,490 rpm @ 65 mph to 2,873 rpm @ 75 mph
5% slip w/3.25:1 axle : 2,411 rpm @ 65 mph to 2,782 rpm @ 75 mph
3% slip w/3.25:1 axle : 2,543 rpm @ 70 mph to 2,724 rpm @ 75 mph

My goal is to go for the 3.25:1 axle ratio but I will know more once I get the transmission stage of my build done and see what I am looking at in the real world.  But based off this, with a 3.25:1 axle ratio with my tire size I should be capable of running 65 mph to 75 mph between 2,400 - 3,000 rpm which is ideal for me.  Here in Texas we have highway speeds of 60 to 75 where I drive and even on I10 leaving Houston where it is 60 mph everyone is going 70 and 75 already and if you try to run 60 you will get ran down.  So in my case gearing to put the speed I will be going 65 to 75 with in my cruise rpm as much as I can is what determines my axle ratio to be.

I also have a gear chart that lists the most common gear ratios with the most common tire sizes and gives you the rpm as well as a yellow, black, and blue lines.  yellow is for economy, black is for balance and blue is for out right pulling power.

for a 3.21:1 axle on this chart which is the closest to the 3.25:1 I am looking at with a 30" tire and 31" tire since mine is 30 1/2" it is putting me at 2,337 and 2,261 rpm outside of the fuel economy range as it is too low of an rpm but this chart does not account for slip that automatics have which will result in an elevated rpm range.  Like right now my C6 is worn out with some 12 or 13% slip where my 2.75:1 axle ratio with 30 1/2" tall tires has me turning 2,750 rpm @ 75 mph currently when I should be turning around 2,400 rpm as my effective axle ratio is 2.49:1 with the taller tires.

But based off this chart for best economy with my tire size not account for transmission slip it says I should go for either a 3.42:1 or 3.55:1 which would put me around 2,500 to 2,600 rpm.  In reality it would put me over 3,000 at the speeds I will have to travel but at 55 mph it may be perfect.  But you cant go driving on the highway at 55 mph when the posted limit is 75 and everyone else is doing 90.  I would get pulled over so fast for not even going the speed limit.

I also found if I go with a 3.25:1 which is my goal with the 8-tooth drive gear cut into the output shaft for my C6 I would need a 17.06 tooth driven gear and ford happens to make a 17 tooth driven gear that will work for me.

But this is my setup though, other peoples setup will vary.  Mine I am piecing my truck together to work with one another on my parts, its why I selected the roller cam I did as its 1,400 - 5,400 rpm power band with a 2,400 - 3,000 rpm cruise range which allows me to run a little more axle ratio to offset my over sized tires and when used in conjunction with the E4OD planetary gear set to get a lower first and second gear of 2.72:1 first and 1.54:1 second (stock was 2.46:1 first and 1.46:1 second) my towing capability should easily be bumped up to at least 9,000 - 10,000 lbs.

With a 3.25:1 axle ratio with stock C6 planetary, my final drive ratio would be 7.99:1 first, 4.74:1 second, and 3.25:1 third at the rear wheels.

With a 3.25:1 axle ratio with the E4OD wide ratio upgrade, my final drive ratio would be 8.84:1 first, 5.00:1 second, and 3.25:1 third.  This is why the E4OD planetary wide ratio upgrade will be done regardless if I go 3.00:1 or 3.25:1.

This here should allow my 306 to be right in the cams sweet spot while cruising down the highway.  In this sweet spot I believe efficiency will be high enough that I should see a decent fuel economy on the highway.

The problem lots of people make is they dont gear for the speed they are wanting to go and thus they end up limiting themselves.  Sure I could throw 3.55:1 gears on my truck and make it a stump puller with the E4OD set but then that limits my speed I can go on the highway and keep the engine in the sweet spot of 2,400 - 3,000 rpm.