The second test duplicated the first, with the only addition being the HVH "Super Sucker" carburetor spacer. Results are as follows:
Brake Specific Fuel Consumption
5000 413.2 393.4 105.0 .48 5100 405.3 393.6 104.7 .49 5200 398.8 394.9 104.1 .50 5300 402.1 405.8 104.6 .50 5400 396.9 408.1 104.4 .49 5500 390.4 408.8 104.5 .50 5600 387 .2 412.9 103.7 .50 5700 379.8 412.2 102.9 .50 5800 377.1 416.4 102.7 .51 5900 378.6 425.3 102.8 .50 6000 372.6 425.7 102.4 .50 6100 370.9 430.8 102.4 .49 6200 369.0 435.6 102.7 .51 6300 367.3 440.6 102.6 .52 6400 367.1 447.3 101.4 .51 6500 353.7 437.7 100.7 .52
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 just went out the window. Keep in mind, this wasn't a 2-inch-tall spacer. It was a simple 1-inch-tall job; one that could fit under the hood of plenty of street-driven vintage Vettes. In theory, the 2-inch-tall model could have made even more power. So how in the world does this thing work? Keith Petelle of High Velocity Heads explains, "These spacers work by helping the fuel distribution. If you look at the bottom of the spacer, you'll see that the shape is different. The reason 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. Plenty of people are skeptical. We've even had some used on high-horsepower race engines. Many people will think if they spent big money on a hand-fabricated intake manifold then they don't need a spacer. We've had some racers with very powerful engines see major gains. The spacers don't discriminate between expensive, high-horsepower engines and low-cost, low-horsepower street engines. They also work equally well on either small displacement engines or big ones. We typically see power increases in the range you found. We've seen more, but it really does depend upon the engine and the type of manifold used."
HVH machines all of their spacers from a proprietary 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. Spacers range in price from $85 to $105. Not cheap for a spacer, 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 available from a carb spacer. It just goes to prove that in the quest for more performance, one can't take anything for granted.