Ask Away! with Jeff Smith: Comparing EFI vs. Carburetion on a 6.0L LS Swap

I’m considering swapping a 6.0L truck LS engine into my ’69 Chevy pickup and I’m trying to decide which intake system to use. My engine has the stock plastic, truck intake manifold and injectors but I don’t have a wiring harness or a computer. Would it be cheaper just to buy an intake manifold and carburetor or stick with the stock EFI system? I have plans to modify the engine with a cam and maybe a set of heads. I have a feeling that the carburetor is cheaper but I’m not sure.

E.D.

Jeff Smith: This is a great question. This looked simple until we got into all the part numbers involved! For the EFI side, you mentioned that you eventually want to modify the engine to make more power. A stock LQ4 6.0 has tremendous potential but is limited by the size of the fuel injectors. The stock injectors on the early 6.0L LQ4 engines flow 25 lbs./hr. of fuel. Without going into a ton of detail on how to calculate this, these injectors are capable at 58 psi of fuel pressure of about 400 to maybe 425 horsepower if you really push them to the limit. Since the engine is capable of 450 to 475 horsepower with just a cam and a set of headers, larger injectors will be necessary.

Injectors can be purchased new or used—and it should not be difficult to find a set of 30 to 36 lb./hr. injectors that would flow the necessary fuel. While we’re on the subject of fuel, you will also need a pair of quick-disconnect fuel line adapters to mate the stock truck fuel rail to an AN hose. Aeromotive sells these adapters and they work very well.

Next, you’re going to need access to the stock truck ECU to change the tune to compensate for the larger injectors and also to add some ignition timing to help power. JET Performance has just come out with its Full Spectrum Tuner that will allow you access to the ECU and make changes to fuel, spark, idle and any other improvements you want to make. JET’s Full Spectrum Tuner is a little less expensive than the HP Tuner or EFI Live versions and accomplishes the same tasks. Of course, you have to know how to use all the power this tuner offers. If you are not computer savvy, you can buy a tune which can be downloaded onto your computer for a price similar to the JET tuner.

You’re also going to need a wiring harness for the engine. If you had the stock harness, you can certainly use it although they are very messy and have all kinds of connections you won’t need for use with your early Chevy pickup. A better solution is an aftermarket harness like those from Painless. We’ve listed all of the above changes in the accompanying chart and the price comes in around $1,126.

One additional cost will be fuel delivery. Even if you go with the carburetor, you will still need an electric fuel pump because there is no mechanical fuel pump on an LS engine. If you go EFI, I’d suggest converting your stock tank to the Aeromotive Phantom fuel pump conversion. This will place a very efficient fuel pump in the tank where it will pull fuel right down to the last gallon without sagging or bogging due to lack of fuel pressure. Look up the Phantom system at aeromotiveinc.com. I have one in my fuel-injected El Camino and it works great.

The second option is to go with a carburetor and an intake on your LS engine. Before we get to that, removing the stock ECU immediately eliminates ignition control. MSD comes to your rescue however with an electronic controller that takes rpm input from the crank and cam sensors and allows you to easily determine the proper spark curve. Even better, this controller is simple to connect and is very affordable. Next, you’ll need an intake manifold. For a street 6.0L, we’d go with the Edelbrock Performer RPM dual plane. Finally, you’ll need a carburetor. For the street, you can’t get much better performance than by going with the classic Holley 0-3310C 750 cfm vacuum secondary carburetor. This is especially true because you can buy a brand new one for only a touch over $350 from Summit Racing. Add up all the prices for these parts and the bill comes to just over $1,000. If you already have a carburetor, then the bill plummets to about $650!

Comparing the two, you can see that the carbureted version is a little less expensive but won’t give you the ultimate fuel control that you would get from a 21^st Century ECU. On the other hand, if you’re not comfortable with laptops and electronic tuning, then the carbureted version is both simpler and attractively priced.

There are dozens of versions of the parts we’ve selected that will affect the price, but the cost comparison is still valid. All you have to do now is decide!

Parts List Price Comparison