Pros and Cons of Carburated LS Motors (photos)
If you are retrofitting an LS engine, you might be wondering if you ought to use EFI or stick with a carb. Here are some things to keep in mind while trying to figure out which to use.
1. Price
If you are retrofitting an old car, and you don't have a complete LS powered parts car to pull from, chances are a carb is going to be cheaper. You can use any carburetor, it can't see what motor you bolt it to, it can only sense the pull of the intake vacuum. You will need to buy an LS carb manifold and a stand alone ignition computer like the MSD LS1/LS6 ignition controller (part no. 6010) which comes with its own plug and play harness for about $650. You'll also have to add a low-pressure electric fuel pump, as the LS has no provision for a mechanical one. You save money and time in not having to change fuel lines, wiring, throttle linkages, etc, and by being able to tune the carb yourself.
2. Weather
Of course, anyone who is older than 40 and has lived in the snow belt will tell you how much better EFI motors are in cold weather. The computer instantly reads the ambient and engine temps and richens up the fuel injection. There is no stuck choke causing fouled plugs, or not engaging to cause stalling when cold. Likewise, when summer comes, a carbed motor can vapor lock, or overheat, while EFI systems don't vapor lock, and cool the motor with a richer mixture. Even with a carb though, you will get the modern LS cooling system and an ignition that adjusts via computer (unless you also ditch the crank sensor for a distributor).
3. Mileage and Power
Carbs are not as accurate in responding to the needs of the motor as a computer controlled EFI with all its sensors, so getting good mileage is harder. Drive a car with an old school carburetor conservatively with a good tune, and you'll get good mileage, but who want to drive that way? At WOT though, the two systems are pretty even, and it all depends on how big your carb is. The EFI advantage is that a large throttle body is much better at small throttle openings than a big carb would be.
4. Tune it by Hand
If you are an older guy, who grew up tuning carburetors, then you are going to be more comfortable with a screwdriver and a box of jets than a laptop. As mentioned before, tuning the carb is the same no matter what engine it is sitting on top of. But, if you are just getting into cars, and are comfortable with technology, tuning fuel injection is easier. However, you will have to replace or add onto the factory computer, which can cost as much as the whole carb/ignition/manifold set up. If you want the optimal tune with either system chances are you are going to be paying for dyno time.
5. Durability
Carburated engines run richer for safety sake, too lean causes detonation, increased heat, and hydrocarbon emissions that are off the chart. But, all that unburned fuel can wash the protective oil film off the cylinder walls, particularly when starting the car. EFI cars don't have that issue, and that is why their motors can easily last 200k miles without a major overhaul.
6. Emissions
If you are doing an LS motor retrofit into something that still has to pass smog tests, you are much better off using EFI. Tune the carburetor accurately and you may pass the tailpipe test, but a knowledgeable tester will spot the motor swap. Most states, however, allow updating a car/truck to a more modern drivetrain, as long as it meets the updated standard. An LS motor swapped into an 80s truck can be just as clean as it was in the 2000s truck is came out of.
7. The Old School Look
If you want the old school traditional look of an air cleaner between the V of that LS engine, you have 2 choices: 1) use a carburetor 2) spend money on a carb type intake and central 2bbl throttle body. The tuned port composite intake on an LS motor is a dead giveaway that you have modern power. Are you trying to blow folk's mind when you open the hood? Or fool them into thinking you're clapped out street racer is mostly stock?
For help tuning and maintaining your LS powered car, check out the how-to section of LS1Tech.com