New LS7 Castings
GM's LS7 castings are arguably the best factory small-block cylinder heads ever conceived. RHS set out to improve upon them with its new Pro Elite LS7 heads, which are available in both 291cc and 307cc configurations. "Improving upon the factory LS7 head design was not an easy task, but we looked outside of the box to determine what could be done to improve it. What we came up with is a raised intake port opening to provide a better line of sight from the intake manifold to the back of the valve," Feeney explains. "The key to making this work was adding material to the intake face to maintain compatibility with the stock LS7 intake manifold. The 291cc head features our standard CNC port, and the 307cc casting is designed to provide additional volume and airflow for larger displacement applications. The ability to build 502ci LS engines these days increases the airflow demand on the cylinder heads, and the 307cc castings are more than up for the challenge. We also incorporated a six head bolt design and increased the deck thickness to provide additional clamping capacity and improve head gasket retention."
Raising the intake runners is a common technique employed to improve intake port airflow. On the other hand, raising the runners too much can compromise the cylinder head casting's ability to support the valvetrain hardware. As such, RHS has employed several strategies in its LS7 heads that offer the superior airflow of a raised runner design while ensuring valvetrain stability. "Raising the intake runners is nothing new, as it has been going on for years and the improvements seem to apply to just about every application. It is effective because it improves the line of sight, and gives the air/fuel mixture a straighter shot from the intake manifold into the cylinder," Feeney says. "The key is to be able to package the raised runner into the existing envelope so you can still utilize the stock valvetrain. Otherwise a custom rocker system is required, which raises costs significantly. In the case of the LS7 heads, the OE rocker design is very good. Consequently, we designed our head to use a rocker stand versus the cast-in pedestal the OE head uses. This strategy allows engine builders to use the stock rockers with a bolt-on stand while retaining the option of installing an aftermarket shaft-mount system for greater adjustability and longer valves in high-lift applications."
Both the RHS block and LS7 heads are configured for six head bolts per cylinder, whereas the factory LS design only has four. Not surprisingly, the six-bolt design has become very popular in power adder applications. "Although we don't have any statistical data to provide on the clamping force, suffice it to say that the four-bolt design is adequate for stock motors and your typical naturally aspirated street/strip combination that makes moderate horsepower," Feeney explains. "However, when you get into the high-horsepower, large cubic inch, and boosted applications, the six-bolt design is essential in increasing the clamping force and improving head gasket retention. In addition, RHS has increased the deck thickness on the block and heads to add additional rigidity in this area."
Gen I Manifold
Despite all the buzz surrounding the LS-series engine platform, RHS hasn't forgotten about the Gen I small-block. The company has recently released an all-new single-plane intake manifold that promises serious performance gains for engine combinations as large as 434 ci. "Our single four-barrel manifold is designed specifically to fit RHS cylinder heads, but it can be used with all small-block Chevy heads. We incorporated multiple bolt patterns so it can be used with early heads as well as late-model heads with the Vortec bolt pattern," Feeney says. "Although a single-plane manifold is typically used on high-rpm applications, we developed a port design that provides power and a strong torque curve throughout the mid-rpm band. This manifold also features an integral water crossover and idle air control circuit, bosses at all four corners for external water lines, and dual distributor bolt bosses. RHS also offers an EFI version of this manifold that utilizes the same external features as the carb, but has cast-in EFI bungs already in place. The bungs have been rolled over to optimize the entry of the injector angle by aiming it directly at the valve stem."