Carburetor Spacers

The engine we used for our test was mild 355 cubic inch small block Chevy complete with lightly ported small valve heads. It’s an efficient piece. A standard correction of 29.92 inches Hg., 60-degree F dry air was incorporated and the tests were done in a conventional A-B-A format (for the sake of simplicity, the final back up test isn’t included. it duplicated the first test almost exactly). When we ran the baseline test, the horsepower peak was 432.4 at 6,300 rpm. The engine torque peak of 402.8 foot pounds occurred at 5,000 rpm. In truth, this is a pretty nice street engine with good manners. For test number two, nothing was changed, except for the addition of a four hole HVH “Super Sucker” carb spacer.


The little Chevy saw a power peak of 447.3 hp at 6,400 rpm, coupled with a torque peak of 413.2 foot-pounds at 5,000 rpm. Bottom line? The HVH Super Sucker added 14.9 HP and 10.4 foot-pounds of torque. It’s a serious power maker. In theory, the two-inch tall model should have produced even more power. Common consensus regarding minimal power gains with a spacer just went out the window. What makes this thing tick? We presented that same question to 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 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 makes use of a Haas CNC mill to carve out their spacers from solid composite stock. Included in their product mix are spacers for 4150 Holley carbs (1-inch, 2-inch, four hole and two hole), 4500 Holley carburetors (1-inch tall, 2-inch tall four hole spacers), 4412 series Holley carburetors (1-inch tall open, 2-inch tall two hole). Down the road, should there be sufficient interest, they’ll consider creating several different spacer designs for spread bore carburetors. In case you’re wondering, these spacers aren’t inexpensive (they can cost $100 or more), but in our book, that’s still cheap power. For more, check out the accompanying photos.

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High Velocity Heads, 710 John Sevier Hwy, Knoxville, TN 37920 Phone: (865) 573-9151, Fax: (865) 573-9154