If you’re into circle-track racing and live in the Mid-West and West-Coast, you already know that the Holley #4412 500 cfm two-barrel carburetor is one of the most widely used in many racing classes to limit horsepower on short course tracks. Racers heavily modify the carburetor to get the most performance from their engines, but the design isn’t so easy to tune at the track. With the introduction of Holley’s new Ultra-HP 2-Barrel Carburetor however, the new #4412 is a race-ready unit that has many of the same features and benefits as Holley’s four-barrel Ultra HP series carbs.
Compared to the older #4412 carburetor, the most noticeable differences on the Ultra HP 2-barrel are the all aluminum construction that saves nearly 50 percent in weight, the centered air cleaner flange, and the elimination of the choke tower that leaves the 1-3/8-inch venturis unobstructed for maximum airflow. Tuning at the track is made much easier with a knurled curb idle screw that can be easily adjusted by hand, and easily accessible air-bleeds that are moved outward for better airflow transition. The billet aluminum metering block is equipped with all screw in restrictors and emulsion bleeds for infinite tuning ability and features an internal pump passage with a bleed-off that can be tuned for optimum performance. The pump circuit also features an anti-siphon valve in the main body to reduce pump pull over.
The fuel bowl holds 20-percent additional fuel and features dual clear sight plugs to easily make fuel level adjustments. It also features internal baffles to prevent fuel from sloshing around and minimize float level fluctuations during hard cornering or launches. The fuel bowl also features an extended -8 AN fitting which has an O-ring for better sealing and is machined such that it can be plumbed from the other side if necessary. The fuel bowl is also equipped with a drain plug to make jet changes easier.
The Ultra HP 2-Barrel carburetor’s throttle blades can also be adjusted with a set screw for wide open throttle, and the PTFE coated throttle shaft is capped off to prevent dirt or debris from entering, and rides on a sintered bronze bushing that is oil impregnated for consistently smooth operation. Aside from its tuning capabilities and consistent performance, the Holley Ultra HP 2-Barrel carburetor also comes in a polished or Hard-Core Gray hard anodized coating.
According to Holley, short track testing prior to the launch of the carburetor yielded a consistent reduction in lap time of 1/10th of a second right out of the box, with no tuning or adjustments. This race-ready carburetor is also approved for use in NASCAR Late-Model divisions in the Mid and West Coasts, and is pending approval on many other race sanctioning bodies. Holley is also working on producing an E85 specific calibration soon. When combined with Holley high-flow fuel pumps and fuel filters, circle-track racers can definitely end up with a winning combination. For more information, visit www.holley.com.