When it comes to engines and our fiendish desire to make them more powerful, it's often easy to fall into a few traps. This is because there are a lot of wives' tales, myths, and misnomers out there that are all too commonplace. One of these myths that many of us subscribe to is the one that says bigger is better, especially when it comes to engines.
When it comes to carburetors, though, most of us know that bigger is not usually better; we just don't know exactly why. We wanted to find out why, so we grabbed a few carburetors and a pretty common small-block Chevy engine andn headed off to our favorite dyno facility to test the theory. The results were surprising.
The Test Engine
Our test engine is a 305-cid Vortec V-8, which is found in hundreds of thousandsof '80s and '90s GM pickups and SUVs. it's not known for being a superhigh- performance powerplant, but our goal here isn't to make astronomical power numbers but rather to find out which carburetor provided as close to perfect fueling for our particular motor as possible. The road to perfection should include excellent driveability and economy, as well as big power, and these are the criteria you should look at when choosing your own fuel metering device. Big power is useless if your engine won't run properly when the loud pedal isn't planted firmly on the floorboard.
The 305 is mostly stock, except for the addition of an edelbrock Performer RPM Air Gap intake manifold atop the Vortec iron heads, Crane 1.5-ratio roller rocker arms, and a Comp Cams Xtreme energy 268 hydraulic flat-tappet camshaft. We bolted Hedman headers to the heads, fired the motor using an MSD Pro Billet distributor and ignition system, and rotated through a set of Demon carburetors during the test.
The Test Carbs
The carbs ranged from BG Fuel Systems Road Demon to Speed Demon lineups.The smallest of the fuelers was a 525-cfm Road Demon. The Road Demon features high-density cast-aluminum metering blocks, vacuum-operated secondary throttle blades, adjustable jets, four corner idle circuits, a billet baseplate to resist distortion, large-capacity fuel bowls with patented sight glasses, and a contoured choke tower to increase airflow. The other carbs were 650-, 750-, and 850-cfm Speed Demons. The Speed Demon offers upgrades over the Road Demon that include billet metering blocks, optional electric choke or dual squirters, and a new idle-eze baseplate that doesn't require you to drill holes in the butterflies to fine-tune the idle speed and transition response.