Vrbancic Bros. Racing Dyno-Tests our CNC-Ported 24° Musi Heads and Matching Oval-port Manifold.
One of the most popular packages that noted engine builder Bob Vrbancic of Ontario, CA-based Vrbancic Bros. Racing builds for the Top Sportsman/Top Dragster class is a supercharged 555-cubic-inch big-block Chevrolet engine using box-stock Edelbrock heads and an Edelbrock intake manifold. With a 4.250-inch stroke with a 4.560-inch bore, Bob says that this is a conservative combination that not only makes good power but very repeatable power.
“We’re at the high end of the application so you can just imagine how good these heads will be at lower horsepower.” — Bob Vrbancic
A 555-cubic-inch big-block engine with a big ProCharger F1X-112 supercharger can really challenge a set of cylinder heads and the list of options for Chevy’s Rat motor is a long one. For this setup Bob uses the Edelbrock/Musi 24° Victor heads (#61419), one of Edelbrock’s popular race-oriented products with an MSRP of $1083.95 each that was produced as a result of the combined efforts of Edelbrock’s cylinder head development team and Pat Musi Racing Engines.
The 24° heads are factory CNC-ported with large oval port designs that produce an impressive amount of flow right out of the box. These heads feature an extra-thick deck with ample material in the spring pockets for a heavy-duty casting that can be used with a high-lift cam and heavy valve springs. Edelbrock fits the heads with Manley dual-spring valve springs and titanium retainers that are good for up to .880-inch lift. On the exhaust side, the ports are raised .750-inch to improve flow and increase power. Edelbrock manufactures a selection of off-the-shelf oval-port intake manifolds to work with these heads. Vrbancic uses the Super Victor 2 intake for Big-Block Chevy engines #2897 ($627.95).
Bob had just finished building one of these engines specifically to dyno test and get some horsepower and torque numbers with the Edelbrock 24° CNC heads and Super Victor 2 intake. The dyno pull provided peak power numbers of 2,263 horsepower at 7,500 RPM with 1,600 ft-lbs at 7,200 RPM. Bob pointed out that the 555 averaged 1,663 horsepower and 1,434 ft-lbs of torque between 4,500 and 7,500 RPM. “By the looks of the dyno sheet, obviously these heads and manifold are capable of making any amount of power that you’d like to make in any kind of application,” said Vrbancic. “We’re at the high end of the application so you can just imagine how good these heads will be at lower horsepower.”
Brian Hatano is a veteran automotive journalist and former editor of Car Craft, Petersen’s Drag Racing, Sport Compact Car and Motorcyclist magazines.