Have you ever wondered how much your car’s e.t. would change simply by swapping carburetors? Do different cfm ratings, mechanical, or vacuum secondaries really make a difference? These are timeless questions for street car builders, and we thought we’d put this matter to the test.
We collected two performance Chevys and a pile of Demon and Holley carburetors and headed for nearby Los Angeles County Raceway (LACR) for a day at the drags to see how these combinations really perform. For the test we used Brandon Begley’s 12-second ’68 Camaro and Editor Smith’s 13-second ’66 Chevelle. Both of these cars are daily drivers, see regular dragstrip duty, and are typical of what you’d find at your local cruise spot. Just to keep it all straight, we tested the Demon carburetors on the ’68 Camaro and the Holley carburetors on the ’66 Chevelle.
The day of our testing had to be one of Palmdale’s hottest and windiest ever. At 10 a.m. our PerformAire weather station told us we already had a temperature near 90 and a density altitude of 5,880 feet. Palmdale’s actual altitude is 3,000 feet. Since hotter air is less dense, we were not going to set any records, but the conditions would be acceptable for comparative purposes. The track conditions also did not help traction. With each car running a set of Mickey Thompson E-T Street tires, careful starting line technique, and constant air pressure adjustment, we still found it difficult to leave the line without spinning the rear tires.
For each carburetor tested we made several passes and recorded the best e.t. for that carburetor. To get the best e.t.’s possible we played with jetting, tire pressure, and diaphragm springs on vacuum-secondary carburetors. We found very small differences as evidenced by the trap speeds.