Have you ever wondered how much your cars 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 wed 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 Begleys 12-second 68 Camaro and Editor Smiths 13-second 66 Chevelle. Both of these cars are daily drivers, see regular dragstrip duty, and are typical of what youd 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 Palmdales 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. Palmdales 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.