It is hard to go wrong with bolting on a simple four-barrel carb and dual-plane intake, but might fuel injection be an even better choice?

Words and Photos by Richard Holdener

Though currently the country is caught up in the LS craze, let’s not forget it was the original small block that put Chevy performance on the map. It can be argued that the little mouse motor all but revolutionized the after market industry, and truly earned its legendary status with countless wins in almost every conceivable from of motor sports. If you are new to the small-block Chevy scene, try this simple test. Ask any small-block owner, and chances are they have at least one cool story involving their beloved mouse motor.

Despite the popularity of the LS, the original small block continues to be a mainstay of the performance after market industry. Some guys simply will not switch, no matter how good (or popular) the LS engine family is. Many of these diehards also stick steadfast to carburetion. There is certainly an argument to be made in favor of the wining ways of a carbureted small block, but does that mean it doesn’t respond to fuel injection? That, my friends, is what we were here to find out.

The 305 test mule had been upgraded with a COMP XR276HR-10 cam. The cam offered a .502/.510 lift split, a 224/230-degree duration split, and 110-degree lsa.

There is no denying the simplicity of a simple carburetor. Having run numerous small blocks on both engine and chassis dynos, we concur with the notion that setting up any EFI motor is considerably more complex that its carbureted counterpart. The question now is, does that mean that modern EFI systems have anything to add?

Truth be told, both factory and aftermarket EFI systems (like the FAST XFI system on this motor) have a lot going for them. That Ford, Chevy, and Dodge abandoned the carburetor in favor of electronic fuel injection speaks volumes about its potential. The most obvious benefit offered by injection over carburetion is the ability to properly dial in the air/fuel and timing curves for any combination of load and engine speed.

By contrast, the carburetor is very effective at metering fuel under MOST conditions, but try to trim the fuel by 6 percent at just 3,880 rpm with a carburetor and see what happens. Proponents of carburetion counter with the additional power offered by charge cooling, so we thought we’d take yet another look at carburetion versus fuel injection on a typical small block.

Obviously, the only way to do this was to run the same motor with fuel injection and carburetion. To add a little spice to the recipe, we decided to run different intake configurations as well. Like any comparison, this test was not designed as the final word in the debate, but rather to provide additional fuel for the fire.  Both systems provide benefits that may be more or less desirable to the individual, and besides, you will never convert a die-hard carburetor guy over to fuel injection, and vice versa.

The results of this test really were less about carburetion versus electronic fuel injection than the difference in the intake manifold design. The dual-plane, carbureted RPM Air Gap intake offered a decidedly different power curve than the Holley Stealth Ram, irrespective of how the fuel was delivered. Whether injected or carbureted, in the end, it was still a small-block Chevy, and that can only be good.

To illustrate the merits of both carburetion and fuel injection, we decided to apply both to a suitable small block. Rather than choose the more-common 350-inch displacement, we selected a 5.0L, or 305 for those who don’t speak metric. The 305 shared the 3.48-inch stroke of its big brother, but ran a significantly smaller bore of 3.736-inches. The smaller 305 was run in a variety of different cars and trucks, and was even the hot setup for a Camaro back in the late ’80s and early ’90s. Ultimately, the F- body received the 350-inch, L98 TPI motor shared with the Vette.

Using a FAST XFI, we dialed in the air/fuel ratio of the injected small block.

Rather than run the test on a stock 305, we spiced things up a bit by adding a set of TFS Super 23 aluminum heads and a healthy COMP cam. Designed specifically for the small-bore 305 application, the TFS heads dramatically improved the flow over their iron counterparts. Working with extra flow offered by the TFS heads, the COMP XR276HR-10 cam featured a .502/.510 lift split, a 224/230-degree duration split, and 110-degree lsa. We knew the right cam and heads would help better illustrate (and magnify) the differences between the injected and carbureted induction systems.

Run on the dyno in fuel-injected form, the 5.0L produced 370 hp and 349 lb-ft of torque. The injected combo made more peak power, but lost out slightly in torque production to the carbureted combo.

The two-induction system run on the modified 5.0L included our old carbureted-combo standby, the Edelbrock RPM Air Gap intake and Holley 650 Ultra XP carburetor. Always a good combination for a street small block, the dual-plane RPM Air Gap offered an impressive combination of horsepower and torque production. Representing the injected contingent was a Holley Stealth Ram intake. The Stealth Ram was essentially a tunnel ram converted for EFI use with injector bungs. The tunnel-ram lower intake was combined with a box upper manifold designed to accept a dual 58mm throttle body.

305 Chevy-RPM Air Gap vs Holley Stealth Ram Note how the dual-plane intake improved torque production lower in the rev range, while the Stealth Ram offered gains on the top end. The peak numbers differed by just 7 hp and 4 lb-ft, but the carb combo offered as much as 20 additional lb-ft down low. Past 5,000 rpm, the Stealth Ram pulled ahead by 10-11 hp. Though the WOT test showed the differences in power, what it doesn’t show you are things like fuel mileage and drivability, which would likely be better with the fuel injection.

In the end, the two forms of induction system produced similar peak power numbers, with the Air Gap and Holley checking in with 363 hp at 6,100 rpm and 353 lb-ft of torque at 4,500 rpm. The Stealth Ram raised the horsepower peak to 370 hp at 6,000 rpm, but peak torque dropped slightly to 349 lb-ft at 4,800 rpm. Despite the slight differences in peak numbers, the curves were dramatically different, with the carb combo offering better low-speed power up to 4,700 rpm, but the Stealth Ram took over past 5,000 rpm. No matter how you slice it, high-tech or high-torque, carbs or computers, as long as it goes on a small-block Chevy, it’s a win in our book.

Sources: COMP Cams, compcams.com; Edelbrock, edelbrock.com; FAST, fuelairspark.com; Holley, holley.com; Lunati, Lunatipower.com; MSD, Msdignition.com