 Unmodified L92 port is reminiscent of the LS7. Compared to the prohibitively expense of the LS7 heads, the L92’s are a steal and can flow at least 340cfm (ported). Like all other LS heads, they maintain a 15-degree valve angle. |
Rectangular Port--L92 Similar to the LS7 design, but the ports are a little taller and a little narrower. They flow more than cathedral-port heads, but not as much as LS7 heads. In addition to the L92 6.2L engines, this port shape is also used on LS3 engines and some 6.0L truck engines, as well as the Corvette ZR1’s LS9 and Cadillac CTS-V’s LSA supercharged engines. Intake manifold bolt patterns are unique to this port design.
C5R--These heads pioneered the rectangular-port design, but because they require professional finishing, their final shape and size depends on whoever is performing the porting.
LSX Series-- Adjunct to the special LSX cylinder block, these new castings will be available in January ‘09. The list includes LSX-L92 (two versions), LSX-LS3, LSX-LS7, LSX-CT (circle track), and LSX-DR (drag racing). NOTE: Only the LSX-LS7, CT and DR) heads are equipped with the six additional attachments points at the bottom of the casting. They have an 11-degree valve angle, versus the production 15-degree and the LS7 12-degree valve angle.
 Vaunted C5R heads comes as a do-it-yourself “kit,” in that the ports are marginal, awaiting the numerical bogey of the mission. This test head shows the extent of expansion orgy. |
Head-to-Block Compatibility
Because of their comparatively small bores (3.89 inches), LS1 and LS6 engines can only use LS1, LS6 and LS2 heads. Using heads designed for larger engines will cause valve-to-block interference. The larger, 4.00-inch bore of the LS2 enables it to use LS1/LS6 heads, as well as L92-style heads (including LS3, LS9 and LSA engines). The 6.2L engines (LS3, L92, etc.) can use any head except for the LS7 and C5R, while the 7.0L LS7 and C5R blocks can use any LS-series head. LS7 blocks should be matched with heads designed for at least 4.10-inch bores, but 4.125-inch bores are preferable.
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Most LS production cylinder blocks share the came cylinder head bolt pattern and the same size head bolts – four 11mm bolts per cylinder (10 in total) and five upper, 8mm bolts. Early LS1 and LS6 engines used different-length 11mm bolts, but engines from 2004 and later use same-length bolts. LS9 engines use 12mm head bolts.
Non-production blocks, such as Performance Parts’ LSX block and the C5R, offer the same head-bolt pattern as production blocks, therefore will accept all LS heads but care must be taken to select the most compatible heads based on the appropriate bore size. Because of their large bores, heads designed for at least 4.10-inch bores should be used and 4.125-inch bores are preferred, such as the L92/LS3 or LS7 heads; otherwise valve-to-block interference is an issue, as is sufficient cylinder sealing.
The LSX cylinder heads use ten 11mm and thirteen 8mm head bolts, or eight more than a regular-production LS head. That’s more than 50 percent more head bolts than production heads, supplying superior clamping strength.