Chevy Small Block Part 17 - PT. 17: Fresh Off The Old Block

After we found some extra power by installing this simple plastic ring, we began to wonder if maybe a carburetor would benefit from the same. But Holley includes this ring only as an adapter; it's not supposed to make extra power. Carburetor experts and racing engine builders George and Bob Vrbancic both think the extra TBI power came from the fact that a throttle body normally chokes airflow into itself because of the large injectors that hang directly above the venturi bores. Unfortunately, you cannot move the injectors any higher to increase airflow because that'll cause the fuel to spray outside of the venturi. So, instead you can try to improve airflow into the venturi by smoothing its entrance. Apparently, this plastic ring accomplishes that. And installing a tall velocity stack, which has been the normal way to improve airflow into carburetors for years, added just a little more power still, further proving our theory.

Here you can see a close up of our trick mounting system developed to secure the air cleaner adapter ring and K&N velocity stack. No good dyno shop would be complete without a roll of duct tape! Also, check out the fuel pressure regulator built into the back of the Holley throttle body centered between the two hoses. The inlet hose (right) gets high-pressure fuel from the electric pump and return hose (left) sends unused fuel back to the tank.