Volume III, Issue 2, Page 6

By Ro McGonegal - Photos by “Chevelle” Rob Cossack - 02/15/08

A year ago this issue, we posted a lengthy catalog of aftermarket suppliers for the LS engine. Among the entries were the World LS7X cylinder heads (15 and 12-degree versions) that were so new that no one had tried them yet. We’d heard about some ungodly flow numbers afforded by porting, somewhere north of 400cfm. World confirmed the rumor but had no hard figures, only hearsay. Regardless, no one had yet applied them to a Gen-3 engine for a real-world adventure.

These particular 12-degree LS7X castings have not yet graced a short-block, either, but they are absolutely essential to the engine we’ll feature in a few months that is based a 453ci LSX short-block as built by Brian Gruben at Scoggin-Dickey Performance Center. We’ll have a full spread on finished motor (a solid-roller twin-turbo), the car it will power (a pump-gas street rat), and all the empirical data you can stomach.

As the LS7X castings are low-production units, they are shipped in semi-finished form. This is standard procedure and is just like any other reputable vendor would do. When you order bare castings, the valve seats, etc., are in unfinished form. The work performed here was by Matt Hilton at HPS Cylinder Heads. He would routinely charge at least $1,500 to put these castings in bolt-on form, right on par with any other quality cylinder head service in the country. Matt has been porting iron (as well as aluminum) for 15 years and is celebrating his sixth anniversary as HPS the company.

.100 68.38 52.9
.200 140.61 104.7
.300 211.84 143.12
.400 269.6 195.7
.500 318.53 224.11
.600 351.29 248.49
.650 376.41 261.91

Engine owner Justin Brayman opted for Manley stainless steel valves, Comp Cams springs, titanium retainers and spring seats, and a Jesel J2K shaft rocker system.

Before tending to the valve seats, Matt honed the guides for proper clearance (prox. 0.0015 to 0.002-inch for the intakes and 0.0025-inch on the exhausts). World heads feature squared-stamped seats that he machined to accept the giant 2.250-inch intake valves and 1.625-inch exhaust valves.