Small Block LS Engine Dyno Testing Part II - Big Power, Small Budget

PRC's ported L92/LS3 heads paid dividends with peak horsepower of 630 at 6,400 rpm and torque of 570 lb-ft at 5,200 rpm. Horsepower and torque gains were seen across the rpm range with averages of 12 and 11.5, respectively. Horsepower at the peaks jumped by 28 but torque gains were a more modest 9 lb-ft. The real story lies in the torque gains between 5,300 and 6,500 where they started out at 10 lb-ft and ramped up to 20 lb-ft. Neither torque nor horsepower suffered at the lower end of the rpm range.

The final test was comprised of the cam upgrade and TSP's own 100mm MAF, resulting in a staggering 641.2 hp at 6,400 rpm with 578.5 lb-ft. of torque at 5,200. Average horsepower and torque rose by 6.6 and 6.3, respectively, while the peak horsepower jumped by 10.9 with torque peak gains of 8 lb-ft. Although the peak and average gains were modest, the larger cam and higher-flowing MAF started to pick up almost equal amounts of power and torque from 4,900 rpm to the redline without sacrificing low-end power.

PRC Ported Cylinder Heads
L92/LS3 heads receive porting to the combustion chamber along with the intake and exhaust ports. The "rectangular"-port L92 head is patterned after the LS7 head but unfortunately also suffers from the same exhaust-flow deficiency. A shot inside the CNC machine shows the "D"-port-style exhaust port being thoroughly massaged. Although not shown, the PRC combustion chambers are available in sizes from 72 cc to 66 cc.

For enthusiasts looking to make big power at a budget price, TSP's offerings are right on target. LS2-equipped GTOs are prime candidates for an L92/LS3 head and cam package, since the stock bore size is 4.0 as is the L76-equipped G8. The only fly in the ointment on the G8 is the AFM, which requires a compatible aftermarket camshaft or a conversion to a non-AFM valvetrain in order to reap the full benefits of the blueprinted short-block or higher-flowing heads.

Owners of LS1-based Firebirds and GTOs who are looking to build big power, remember that the L92/LS3 cylinder head requires a 4.0-inch bore, and with the maximum overbore that can be achieved on an LS1/LS6 pegged at 3.905 inches, it would be more cost-effective to bolt on a set of PRC Stage 2.5 heads (HPP, Oct. '08) unless you're in the market for more cubic inches and more power potential.

Cylinder-Head Flow
All flow numbers are quoted at 28 inches test pressure. Stock LS2 and L92 cylinder-head flow numbers are from the GMPP catalog. The GMPP catalog does not list flow numbers above 0.600 lift. Ported L92 cylinder heads were tested on Precision Race Components' SuperFlow 600 flow bench.