In an effort to capitalize on the phenomenal performance potential of GM's LS engine family, the aftermarket has released a bevy of cylinder-head castings to cover everything from 3.90-inch (LS1) bore sizes through 455ci strokers featuring up to 4.125-inch bores. You can now add one more player to that list, as Bill Mitchell Racing Products (aka World Products) has finally released its long-awaited Warhawk LS1X aluminum heads.
According to Charlie Amodeo of World Products, "The LS1X head is a clean-sheet design that features factory 15-degree valve angles and is primarily targeted at [customers] looking for excellent power potential at reasonable prices. The heads flow over 300 cfm on the intake and are built with lots of extra material to allow additional porting and airflow gains."
World Products' Warhawk LS1X...
World Products' Warhawk LS1X aluminum heads are available with either 64 or 72cc combustion chambers. Bare heads retail at $1,157.98 for a pair (PN 025150 for 64cc or 025250 for 72cc). The heads have thick (0.650-inch) decks, and the valve-cover rails have been raised 0.300-inch to support aftermarket rocker arms. World also offers fully prepared heads that utilize Manley valves and springs to support either 0.600- or 0.700-inch valve lifts. These retail for $1,724.98 for the 0.600-lift package and $1,869.98 for the 0.700-lift version.
"The heads [in this story] were actually pre-production units sent to us for evaluation and product testing," says Pete Incaudo of VMax Motorsports. "Through a long-standing affiliation with Bill Mitchell and World, we worked toward the goal of getting them very close to what would ultimately be offered by World in the retail market. Since I have performed numerous cylinder-head evaluation tests for GM-including pre-production LS1 castings in 1996-it was a great opportunity to evaluate the World design and provide feedback. In addition to testing the heads on a flowbench, we wanted to see how much power could be generated on the dyno."
Follow along as we install a set of the new LS1X heads on an '02 Z06 owned by Kevin Turner of Carrollton, Texas. Other than a Halltech C5 Venom air-induction system, the car was bone stock prior to our ministrations. To help us extract maximum power from the combo, VMax and Real Performance Motorsports (RPM) spec'd out a nasty combination featuring Kooks headers, a rowdy Comp bumpstick, and a FAST intake manifold with a ported 90mm LS2 throttle body. Installation was performed at RPM HQ in Lewisville, Texas, by technicians Manuel Bejar and shop manager Keith Lohse. Company co-owner Brian Lohse, meanwhile, tuned the combination with HP Tuners' VCM Suite software.
The LS1X heads feature 235cc...
The LS1X heads feature 235cc intake runners similar in design to the "cathedral" port configuration of the LS1 (200cc) and LS6 (210cc) units. This healthy intake-port volume is similar to what you might find on heavily modified stock castings and numerous aftermarket entries.
A closer look at the intake...
A closer look at the intake runners on the as-cast heads shows the amount of work that went into redesigning the short-side radius in order to support intake flow of 304 cfm at 0.650-inch lift.
Before diving further into...
Before diving further into the new World heads, let's take a look at a typical LS1 combustion chamber. These measured 67cc and yielded a 10:1 compression ratio. Note the signature "heart" shape of the chamber.
The LS6 heads introduced on...
The LS6 heads introduced on the '01 Z06 spec'd out at 64.5 cc and yielded a 10.5:1 compression ratio. The redesigned combustion chambers are described as a "closed chamber" type.
A shot of the World LS1X combustion...
A shot of the World LS1X combustion chamber reveals that it has a "modified heart-shape" design optimized for 15-degree valves and rocker-arm-stud angles. The bare casting shown here has 64cc chambers and would slightly increase the compression ratio on an LS6. For owners of boosted vehicles, the 72cc chambers would reduce compression on an LS1 or LS6 to approximately 9.1:1.
As cast, the World exhaust...
As cast, the World exhaust ports flow 218.9 cfm, a substantial improvement over the approximately 183-cfm rating of the factory LS1/6 heads. Described as a "modified oval shape," they're similar in design to the LS1 casting, rather than the D-port LS6. Exhaust-port volume measures 80cc.