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I've been doing alot of thinking the past couple months and im considering swapping from efi to carb. Im getting tired of dealing with a laptop and 10,000 other possibilities to go wrong with efi.
My question is what is all needed on the fuel supply side?
My current combo is as such.
65 chevy 2
Ls3 block (416)
Tfs 235 heads
239/247 112 .625/.625
1 7/8 full length headers to 3" x pipe magnaflow 3" tailpipes.
holley split with 4150 accufab.
term x max, 50lb gm injectors.
3100lb race weight.
12-1 compression
FLT lvl 4 4l60e
Yank ss4000
3.42 gears (changing to 3.90 soon)
26" rear tire.
Fuel system is a walbro 340lph intank with a -6an feed and a -6an return with a tanks inc regulator.
I want to keep the intank pump if possible to keep the pump noise down. Will i have to run larger feed and return lines? The sending unit that holds the pump is a 1/4" npt feed and return( basically 3/8" or -6an) is that going to be a problem?
I'm also wondering a 750, 850, 950cfm holley type carb?
Is the MSD 2014 ignition box the go to?
I'm going to need a stand alone for the 4l60e.
thanks
For MOST people, EFI is set and forget. It keeps AFR the same regardless of temp or altitude.
Carbs do not do that.
That's the major reason it's on EVERY car and truck built today.
It passes today's smog standards while running great.
The last cars with carbs ran like crap.
Even the earliest cars with EFI ran better than before, and the latest ones are light years ahead in performance and efficiency
If carbs could do all that, they'd still be around. But they're NOT.
For MOST people, EFI is set and forget. It keeps AFR the same regardless of temp or altitude.
Carbs do not do that.
That's the major reason it's on EVERY car and truck built today.
It passes today's smog standards while running great.
The last cars with carbs ran like crap.
Even the earliest cars with EFI ran better than before, and the latest ones are light years ahead in performance and efficiency
If carbs could do all that, they'd still be around. But they're NOT.
I'd be more inclined to say the main reason cars have been using fuel injection for the past 43 yrs has to do more with CAFE standards and EPA standards.
No efi is not set and forget......especially when something like a 02 sensor goes out and leaves you stranded along side the road.
Dumb statement. Nothing is maintenance free. Most new cars see 100k miles without anything more than oil and filter changes.
No carb could pass emission regs as they are, NOR get the fuel efficiency EFI affords.
There is no sensible argument for carbs in today's world
Dumb statement. Nothing is maintenance free. Most new cars see 100k miles without anything more than oil and filter changes.
No carb could pass emission regs as they are, NOR get the fuel efficiency EFI affords.
There is no sensible argument for carbs in today's world
Saying an O2 sensor leaving you stranded, especially on a V8 with 2 sensors.
It will run crappy, but not leave you stranded.
But that has nothing to do with AFR or timing adjustments, hence my set it and forget it line.
Saying an O2 sensor leaving you stranded, especially on a V8 with 2 sensors.
It will run crappy, but not leave you stranded.
But that has nothing to do with AFR or timing adjustments, hence my set it and forget it line.
this is the "DUMB STATEMENT ". you assume my car has two 02 sensors when in fact it doesnt. I see you have 0 experence tuning holley. Ill let you know something, when the O2 goes out most of the time it tries making the engine run at 35-1 afr. So yes itll leave you stranded unless you make provisions in the tune before.
It's pretty obvious your anti carburetor so just stop with your negative comments unless you have something useful to add.
I'd be more inclined to say the main reason cars have been using fuel injection for the past 43 yrs has to do more with CAFE standards and EPA standards.
No efi is not set and forget......especially when something like a 02 sensor goes out and leaves you stranded along side the road.
If your EFI is Volumetric Efficiency based, it doesn't need the O2 sensor to run. If it does die, all you need to do to get home is turn the O2 sensor self-tune authority to 0 and it will base fueling entirely on the fuel map and Manifold Air Pressure sensor says.
If your EFI is Volumetric Efficiency based, it doesn't need the O2 sensor to run. If it does die, all you need to do to get home is turn the O2 sensor self-tune authority to 0 and it will base fueling entirely on the fuel map and Manifold Air Pressure sensor says.
yes that is true. I was just using that as just 1 example of something that can go wrong. Ive already had a injector driver go out in the holley and that wasn't fun. Over the last 40 yrs of working on cars ive had both carb and efi. Both have there problems. To me carburetor setups are just less of a hassle for a weekend cruiser like mine.
If you are doing a new build, a carb could be easier to get "good enough". However, With the entire EFI system already in place it should be much simpler to fix what you have than start over. Dealing with an ignition box and trans controller are going to be just as bad as the full EFI system, then you also have to change the fuel pressure regulator and tune the carb.
To be frank this is the Carbureted LSX Forum and it's for people seeking advice on carburetor fuel systems. As for computer controlled EFI systems once the tune is set to the fuel being used you no longer need the O2's or any of the other sensors the ECM needs to command fueling or timing. I guess if you traveled to race the car from sea level to places with high elevations where there's a drastic change in the atmosphere it might pose a problem but the engine is still going to run it just may not be running it's best and adjustments would still need to be made regardless of what fuel system you're using except in cases where the computer is allowed to make it's changes to the fueling and timing based on what information it gets back from the sensors. The idea of not having to rely on computer components to control my engine and transmission the ability to run is quite appealing to me.
Last edited by 01CamaroSSTx; May 14, 2025 at 04:23 AM.
I have not had a carb LS setup that I didnt like yet. Ive had a BIG cam 6.2, all the way to a stock 5.3 they all ran absolutely flawless with out of the box brawler mechanical secondary carbs. I ran a 650 on the 5.3 and all the way up to a 850 on a 6.2, also ran a few 750s just fine on some other 5.3's and 6.0's and I would not hesitate to run those setups again, well I actually am running a carb 5.3 in my ski boat right now with ZERO issues.
With that being said if I already had a running EFI setup AND needed to control my electronic transmission, there is no way id consider swapping to a carb. You will be buying a carb, buying a MSD box, and the trans controller, then having to rewire stuff and regulate your fuel pressure down ....... naaahh im certainly gonna keep the EFI if thats the case.
But for anyone to say a properly running carb is no good...... I dunno what to tell you, they have worked just fine for a LONG time lol.... from weedeater engines to 1000+ Cubic inch race car engines... keep trash out of them and your good to go.
The only time I personally wouldn't run a carb is in a blow thru setup or if I was needing to control the trans like the OP is.
If you want to put a carb on it, put a carb on it. It's your car.
There are pro's and con's to both. If you are more familiar with a carb maybe that's the better way to go for you. It doesn't make sense for you to stick with something you aren't happy with, even though the internet says you are wrong. LOL
EFI works well, very well, but there is a learning curve to it. The "Self tuning" bullshit that every company pushes is, just that, bullshit.
It's marketing that makes people who know nothing about EFI, think it's a bolt on and you never have to worry about it again. That obviously is not the case, then people hate EFI in general or a specific brand(even though there are some junk *** EFI companies out there)
You should be able to use your existing fuel system as is, but will have to change the spring in the regulator to a low pressure spring to get your fuel pressure for the carb.
Speaking of carb, since you are getting one, make sure you get one with a provision for a TPS sensor, you will need that for the trans controller.
I've used the MSD Atomic standalone transmission controller on several cars and have had good luck with them.
Nothing wrong with going carb'd. Since there is no variable valve timing, or other things requiring an ECM, you just need a simple trans controller
I myself am going full Luddite build. 5.3 LS4 stripped down to bare nothing, Holley 830HP, lightened flywheel with a quarter master 2-disc clutch in front of an AR5 trans. The only thing electrical will be the starter, alternator and lights.
I'm contemplating the MSD 6014, or a belt driven magneto.
@65LSXNOVA .... I had this in my bookmarked links for a while and posted in the tech section of a marine forum as well as an old truck forum 4 years back. it mirrors what I discovered in the early 80's and 90's going back and forth between EFI and Carb. https://www.hotrod.com/how-to/carbur...t-on-ls-engine from a performance and fuel economy point of view, a carb is just as good as EFI on an LS since we are not phasing cams, etc.especially if you do not change elevations often, there is generally no re-tune unless you swap parts
for example, I live at 22' above sea level in a state where the highest point is a bridge that goes 210 feet above sea level. the temperature swings between 40 degrees and 95 degrees. I do not even run a choke or fast idle cam on the carbs on any of my project vehicles or the boats. no need to. you live in a state that is relatively flat as well with an elevation of 450-650 ft above sea level. although since you may see colder weather, you probably want a choke.
It is your vehicle, build it the way you want and drive it.
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