Peak in baseline configuration was 432.4 hp at 6,500 rpm. Maximum torque was 402.8 lb-ft at 5,000 rpm.
The second test duplicated the first, with the only addition being the HVH Super Sucker carburetor spacer. Results are as follows:
As you can see, the small-block peaked at 447.3 hp at 6,400 rpm, while the maximum torque of 413.2 lb-ft occurred at 5,000 rpm. In comparing peaks, the Super Sucker added 14.9 hp and 10.4 lb-ft of torque (again at peak).
Our assumptions regarding carb spacers at that point went out the window. And keep in mind, this wasn't a 2-inch-tall spacer. It was a simple 1-inch-tall job. In theory, the 2-inch-tall model should have made even more power potential. So how in the world does this thing work? We asked that same question of Keith Petelle of High Velocity Heads: "These spacers work, obviously, by helping the fuel distribution. If you look at the bottom of the spacer, you'll see that the shape is different. The reason for that is we wanted to improve the feeding of the outside runners on a single, four-barrel manifold. The design picks up the air speed and gives it a specific direction. Finally, the plastic composite material insulates the carburetor."
HVH machines all of their spacers from solid plastic composite stock on Haas CNC-mill equipment. They offer 1-inch and 2-inch-tall, four-hole spacers for 4150 Holley carburetors; 1-inch and 2-inch-tall, four-hole spacers for Holley Dominator carburetors; open, 1-inch-tall spacers for Holley 4412 carburetors; and two-hole, 1-inch-tall spacers for Holley 4412 carburetors. At present, they don't have any other spacers planned, however, if they have sufficient interest, they may consider creating several different spacer designs for Rochester Quadrajet-style carburetors. These spacers aren't exactly cheap, but they do provide cheap power. But in a well-sorted engine, 15 hp for 85 bucks certainly could be considered a bargain.
In the end, our preconceived carb spacer notions were definitely wrong: There is power from a carb spacer, particularly if it is of the HVH Super Sucker configuration. This thing might be the cheapest, easiest horsepower you'll ever find.