We never said a carb couoldnt make the same power. We have taken a big block race motor on the engine dyno with a carb and put holley efi on it and made the same power with less fuel. The issue is "most" people do not have a fine tuned carb or have the abilty to tune a carb and a distributor so they are no where close to where there should be. We add efi to older carb motors all the time and pick up 30-75hp going to efi, but the gain is because we are tuning the efi and the old setup wasnt properly tuned.

 

Now that is interesting! I bet a person with some contacts in China to make cast aluminum intakes to mount 4 x 2 barrel Webers on LS engines with cathedral port heads could make a pocket full of money selling the carb/intake/linkage combo for like 3.5k a pop

Personally I don’t care what people run but I do prefer some creativity and the willingness to take some risks when they are creating something special like a LS swapped car

The carburetor I’m using now is a Quadrajet (especially for the haters)

 

do you not realize the fact that an engine has to pull THROUGH the rpm range and peak power of your shitty intake manifold is killing your acceleration. 55ft lbs list is a **** ton and will make it feel like a dog.

 

then I guess the answer is, no I haven't been disappointed in my ls swaps compared to sbc because I actually use a proper combination instead of a giant intake on a tiny motor with the worst 4150 carb money can buy. but you do you and now you can tell your friends that those new fangled LS motors are trash compared to that glorious sbc

 

This is all anyone needs to know about this thread. If you're reading/responding for any reason other than entertainment, you're wasting your time.

 

Actually that's not a true statement either and likely the opposite is true. Unless you have one O2 sensor per cylinder EFI is no better than and sometimes worse than a carb for keeping the proper AFR in each cylinder. I'll give a simple opinion as I understand it...(I've been wrong before lol), The carb sitting above the intake and being a wet system means that the AFR is set before it's distributed to each cylinder so each cylinder will have an AFR that is the same in mixture, The volume of charge each cylinder gets depends on the intakes ability to distribute the volume evenly and most intakes are pretty good at it but not great. This is where the old one carb per cylinder setups were able to shine.
EFI on the other hand injects the same amount of fuel into the cylinder regardless of the volume of air that is pulled in, If there is a problem with air distribution then you can have cylinders getting less air than another yet getting the same shot of fuel from the injector. If you do a search you'll see that intake distribution problems have carried over to EFI intakes as well. Then you also have the issue of injectors that flow varying amounts of fuel per pulse, I you have a known flow matched set and they never get dirty/clogged then you're all set in that aspect. Unless you have a system that uses one O2 sensor per cylinder to monitor and adjust each separately the O2 reading is just an average meaning one out of range can have an effect on all other cylinders.

The thing that makes EFI so good is it's ability to adjust to barometric/temperature/load changes among others that added together mean a more efficient running engine. One thing you never have to worry about with a carb is a failing injector burning up a piston.(sarcasm)

 

wet flow can be more difficult to get even because fuel has a much higher mass than air so it can come out of suspension around turns and stuff.
my opinion is having individual injectors at the heads is going to be more even because uneven dry air will be less uneven than uneven wet air. but I'm a nobody.

 

I'm not arguing that carbs are better, Just that they aren't nearly as bad as people try to make them out to be. I made the switch long ago and won't be using them unless it's someone else's vehicle. I just pulled a rebuilt carbed 350 from a sprint car I bought, Someone else started to make it street legal and I bought the project. It's getting an LS infusion with Inglese efi stack injection. I get the look of traditional stacks sticking out of the hood with the benefits that EFI and the LS engine offers. Car should weigh about 1,600lbs and have about 450hp...Should be a pretty quick street car lol
I did find out something that I didn't know while attempting the swap... The LS is slightly wider than the SBC, I did a search before I tried dropping it in and lets just say there are a whole lot of people posting the wrong information, It's only a small amount but it's enough to keep the motor from fitting without redoing that section of the chassis.

 

The challenge is the fuel can and does drop out of suspension in the airstream BEFORE it gets to the intake valve. So it's very common on this type of carbed set up for cylinders to get different mixtures. Even worse than a single carb on a V8 is a single carb on an inline 6.

.....and I violated my own counsel....

 

Bingo....

 

an ls swapped car is special? Maybe you are special too?


quadrajunk? Good choice. This junk keeps better and better.


folks I think this thread was made as a joke and to ruffle feathers. It can’t be serious. I think it’s just for boredom entertainment.

 

Again not nearly as much as people think and certainly not enough to matter with most builds, I watched them on the dyno to many times to count and recently quite a few with 8 O2 sensors and EGTs monitored. You have to remember that there are still tons of cars/trucks running carbs and with as many dirt tracks as there are in the Midwest that don't allow injection and people that haven't made the change on their drag cars/ street-strip car cars there are still a shitload of carbs being used regularly.

 

theres definitely tons of carbs still out there, but unless you really really know what youre doing with a carb, efi is going to give you a better tune. high end cars have access to some excellent carb tuners, typical street guys with their selection of holley main jets simply wont be able to get as refined as they could with a basic modern ecm.
i played that game for a while with emulsion jets and air bleeds and frankly its a nightmare and i just never felt like i was making progress.

 

i just picked up a '77 k5 to swap and the carbed 350 goodwrench motor runs so nice i've kinda lost interest lol.

and to top it off, out of 7 cars it's the only one that doesnt leak a little oil

 

i agree. I have one on my lawnmower and my weed eater. So there’s two added to the amount used. Lol

 

You should definitely do a cam swap into the ls before the swap if you do it....according to the people posting here the stock cam is so shitty it won’t even run with a single plane intake (unlike every other V8 engine produced since the beginning of time lol)

but seriously the truck 5.3 and the 350 are not all that different unless you change the cam on the ls and it makes sense since ls or not it’s still emissions friendly in stock form

 

You aren't listening. You installed an intake with a powerband of 2500-7000 when you only plan on shifting at 6000. Chances are that advertised powerband is for a 5.7 or 6.0, so you are shifting well before peak power is obtained since the smaller cubes move everything up. The factory truck camshaft is designed for low-end power, and I believe factory shift points are at 5500. So, you're winding a camshaft 500 RPMs outside of its powerband while starving an intake of at least 1000 RPMs worth of air, and you are wondering why the motor isn't performing to expectations?

And this is all before we take a deeper dive into the compression and exhaust sides of your engine.

And this is coming from someone with a 404 LS stroker, an NA 5.3, and a Vortec 355 all sitting in the garage.

 

with all due respect (none actually) you sir, are not very smart and you are stubborn as ****.


hey guys, let’s leave this hardhead alone. He knows everything, yet he knows nothing. We are wasting our time. I think this guy’s original intent was to dog on the ls motor and imply that a sbc is superior.

 

yes, you are definitely wasting your time trying to tell me how to build an engine since you have no idea who I am, what I've done or what I know. You're doing nothing but making assumptions and spitting out information I already know and didn't ask for. The fact is I don't particularly like the SBC and never said a bad thing about LS engines. If you actually think the SBC is so terrible that comparing a high performance 350 to a 5.3 bone stock truck motor is not fair then it is you sir that is not very smart because you are clearly not commenting based on your own personal knowledge. You're just defending the LS based on an assumption that I am comparing it to something so inferior that the comparison is unfair.....assuming I have the LS setup is so bad that's the only possible reason I could even suggest any sort of comparison between the two.

So to all the haters spitting out the insults please allow me to respond in kind: your mom

 

Yep. Had a friend at 18 years old do a stock rebuild on a '79 olds 403. .o24 over, stock replacement hyper pistons, stock poor flowing heads and what would come out to around 7.9:1 compression, stock intake and a set of headers. He was going to be a hero by adding a Comp "292" cam. All said and done he put the "beast" in front of a th350 with a stock stall converter. The choppy idle sounded nice, but the car wouldn't get out of its own way and could barely muster spinning the rears with a brake stand. Just a dog everywhere. He got a good education from that build and learned that parts need to be matched to work properly, now 20 years later he owns his own performance shop. Humility is what leads to progress in a lot of cases.