Hotrod magazine LA BUILD VERSUS LS

The intake manifold was a large challenge for the project. Besides adapting the W2-style bolt pattern to the W5-pattern heads, the passages had to be reshaped to match the intake ports. It took Valley Performance’s Jack Barna two months of scouring the internet before he found the vintage Holley Pro Dominator tunnel ram.

The manifold’s intake runners were originally D-shaped and didn’t line up with the heads’ intake ports, so Valley Performance went to work reshaping them until they did. The goal was to make the runners blend with the ports, with the larger radius of each runner at the top to optimize velocity.

Despite the comparatively small 376ci displacement, the airflow capability of the heads and intake manifold demanded significant fuel and air delivery, so a pair of 880-cfm four-barrels from Pro Systems Carbs (with annular boosters) were crafted by Patrick James.

The carbs are used with anti-reversion plates — also known as shear plates — to help prevent high-rpm airflow reversion. They’re designed to redirect hot gases that can rise into the manifold via camshaft overlap; and with a tight lobe separation angle of 106 degrees on this engine’s cam, that’s a concern.

An MSD crank trigger system was selected for more precise cylinder-to-cylinder ignition timing. With it, the conventional distributor mounted on the engine is essentially gutted, containing only the rotor and shaft to support the secondary ignition.

The headers are from Schoenfeld, with 1-3/4-inch-to-1-7/8-inch stepped primary tubes and 3-1/2-inch collectors. Valley Performance cut the collectors from the primaries and experimented with various primary lengths on the dyno, finding the original length delivered the best average performance.