Chevrolet’s LS engine platform has turned into the small-block Chevy platform of choice for many racers and enthusiasts alike – it offers incredible performance and longevity when configured properly, and will survive a ton of abuse in the process. When building an LS-platform engine for ultimate performance, one area that can be improved is the choice of cylinder head. Mast Motorsports has the solution with a pair of cylinder heads aimed squarely at the racing marketplace. 

The company’s PXR cylinder head offers an inline-valve arrangement, with both intake and exhaust valves placed at 12-degrees, splayed three degrees from the stock 15-degree arrangement.

They are designed for use on any Gen II/IV small-block LS engine using a 4.125-inch or larger bore and offer the prized six-bolt head retention design, critical in applications where large boost or nitrous use is expected, and are compatible with GM’s LSX, RHS, and World LSX engine blocks along with Dart’s new LS Next block.

The 290cc intake ports feature a raised-runner design for improved flow, and large 2.200-inch intake and 1.600-inch exhaust valves are used. Ultimate flow numbers exceed 400 CFM on the intake side and 250 CFM on the exhaust side when paired with appropriate equipment, and Mast offers a two-piece CNC intake manifold that pairs up nicely with the PXR’s design. 

For all-out applications where no compromises are necessary, the canted-valve Mozez Race head (seen at top) is the ultimate in LS-derived performance. Like the PXR head, it uses the six-bolt retention arrangement and is designed for all of the hot-ticket engine blocks like the LS Next and RHS offerings. Valve angles are 10 degrees on the intake with a 4 degree cant and 7 degrees on the exhaust with a 2.5 degree cant. Ultimate flow numbers of 458 CFM intake, 281 CFM exhaust are present at a whopping .900-inch lift. The huge-by-large 352cc intake ports will swallow as much air as you can cram inside. These are the ultimate cylinder heads for LS race engines.