CNC Ported L76/L92 Heads - Car Craft Magazine

To keep our GMPP LS3 factory fresh, we elected to run CNC-ported L76/L92 heads from GM Performance Parts. The GMPP L92 heads featured a factory valvetrain, including a 2.16/1.59 valve combination and stock springs that are marginal even with the stock cam. GMPP offers a set of LS6 (blue) springs as an upgrade.
To keep our GMPP LS3 factory fresh, we elected to run CNC-ported L76/L92 heads from GM Per
Looking deep into the 280cc intake port of the GMPP L92 head revealed extensive porting. The ported GMPP L92 heads flowed 332 cfm at just 0.600 lift, or enough to support more than 650 hp.
Looking deep into the 280cc intake port of the GMPP L92 head revealed extensive porting. T
Exhaust flow from the 100cc port was equally impressive at more than 225 cfm with a flow pipe.
Exhaust flow from the 100cc port was equally impressive at more than 225 cfm with a flow p

The factory rockers were retained for all testing. In addition to the obvious difference in port shape, the LS3/L92 heads differed from their LS1/LS2 cousins because of the use of offset rockers on the intake valves.
The factory rockers were retained for all testing. In addition to the obvious difference i
Wanting to eliminate any trace of valve float for those occasional trips to 7,000 rpm, we replaced the factory springs with beehive springs from Comp Cams (PN 26918). The head swap improved the peak power from 492 hp to 503 hp, while torque jumped slightly from 484 lb-ft to 497 lb-ft.
Wanting to eliminate any trace of valve float for those occasional trips to 7,000 rpm, we
After running the new heads, out came the wimpy stock LS3 cam to make room for the Comp 281LRHR13 grind.
After running the new heads, out came the wimpy stock LS3 cam to make room for the Comp 28

Note the difference in the snout design of the two cams. The stock LS3 featured a single retaining bolt, while the Comp performance cam featured the earlier three-bolt design. Comp also offers the single-bolt cam cores.
Note the difference in the snout design of the two cams. The stock LS3 featured a single r
This shot illustrates the three different cam sprockets available for the LS family. The LS3 (bottom left) featured provisions for the front-mounted cam sensor and a single retaining bolt. The LS1 (bottom right) featured three retaining bolts but no provisions for the front-mounted cam sensor. The top sprocket required for installation of the three-bolt cam into the LS3 (GM PN 12586481) featured the three-bolt retaining pattern and the provisions for the cam sensor.
This shot illustrates the three different cam sprockets available for the LS family. The L
After installation of the Comp cam, the power output of the LS3 increased from 503 hp and 497 lb-ft to 569 hp and 522 lb-ft. Every bit as important as the peak power gains was the fact that the power increased throughout the rev range.
After installation of the Comp cam, the power output of the LS3 increased from 503 hp and