With the majority of the short-block assembled in Part I, the L92/LS3 engine is ready to be completed and then tested on the dyno. To recap the build, in Part I Texas Speed and Performance (TSP) used a brand-new GM 6.2L aluminum L92/LS3 block as the foundation to build a 418ci engine. TSP utilized the services of Sunset Racecraft in Lubbock, Texas, to bore the block to 4.080 inches (4.065-inch bore is stock) and then install a custom Eagle 4.00-inch stroker crankshaft, Eagle connecting rods, and Diamond Racing pistons. Texas Speed completed the buildup with its own Texas Speed/Precision Race Components (PRC)-prepped cylinder heads and accessories.

According to Trevor Doelling, co-owner of TSP with Jason Mangum, "The key to the power potential of the 418 lies in a blueprinted short-block that has undergone extensive development and testing before it reaches the market. Working in conjunction with the manufacturers and Sunset Racecraft, we developed engine packages that offer value and performance. For enthusiasts with an LS engine with a bore of 4.00 or greater, the factory L92/LS3 head can be utilized and flows almost 320 cfm on the intake in stock form. By developing a five-axis CNC-porting program, we achieved a higher-flowing head that improves upon the factory velocity and provides a much more balanced intake-to-exhaust flow ratio," (66.4 percent vs. stock 59.8 percent).

Retailing at $4,095, the TSP short-block is offered in both 418 and 427ci versions (PN 25-418LS3LB or 25-427LS3LB) and is a solid foundation for a serious LS-series build. The long-block costs $7,399 (PN 25-418LS3LB or 25-427LS3LB). Follow along as we complete the assembly and dyno test the TSP 418.

Dyno Testing
All testing was completed on Sunset Racecraft's Dynamic Test Systems' (DTS) model 4000G dyno. HP Tuners VCM Suite was used to tune the computer, the timing was locked at 28 degrees, and the knock sensors were removed for testing.

VP 101-octane unleaded was utilized in the cell (TSP says 93-octane would work just as well), fed to the engine via the shop's Aeromotive fuel pump, and regulated to 58 psi. In order to ensure consistency in the test results, the various combinations were pulled after the engine had recorded 165 degrees on the test cells' DTS model S-1007M engine-cooling system. No engine-accessory belts were required since a Meziere electric water pump was utilized.

Once the engine reached temp, the dyno operator took it to 3,800 rpm and then applied a dyno load. Once loaded, the engine was slowly brought up to 3,000 rpm and pulled until the specified redline. Standardized SAE calculations were used to correct the horsepower and torque to industry standards.

Dyno Test Configurations
Test No. 1 - (Baseline) - Stock L92/LS3 heads, P.T.M. 92mm throttle body, SLP 85mm MAF, stock L76/L92 intake, and Comp Cams hydraulic roller camshaft with 242/248 duration at 0.050 and 0.612/0.615 lift on a 114 LSA

Test No. 2 - Replaced stock L92/LS3 heads with PRC ported L92/LS3 heads

Test No. 3 - Swapped to a Comp Cams hydraulic roller camshaft with duration of 251/259 at 0.050 and 0.660/0.603 lift on a 111 LSA, replaced SLP 85mm MAF with TSP 100mm MAF

Results:
Baseline numbers for the 418 were an outstanding 608 hp at 6,300 rpm with 561 lb-ft of torque at 5,200 rpm. At the lowest recorded rpm of 4,000, the engine was already making 487 lb-ft of torque with 371 hp. Horsepower jumped over 500 at 4,800 rpm and crested the 600 mark at 5,900 rpm through the redline of 6,500. Most impressive was the torque, which exceeded 500 lb-ft from 4,100 to 6,300 rpm. Average horsepower and torque from 4,000 to 6,500 rpm checked in at 531.5 and 532 lb-ft, respectively.

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.

Cylinder-Head FlowLift at 0.2000.3000.4000.5000.6000.650
LS2 Intake136195237260260
LS2 Exhaust104135157169180
L92/LS3 Intake151208256294316
L92/LS3 Exhaust111152174183189
PRC L92/LS3 Intake154223282323349356
PRC L92/LS3 Exhaust117179202219232237
Valve SizesIntakeExhaustValve Angle
LS22.001.5515 deg
L92/LS32.1651.5915 deg
PRC L92/LS32.1651.5915 deg
High Performance Pontiac
Engine Buildup Worksheet
Engine Displacement418ci
Bore/Stroke4.08/4.00-in
Block/Crank ComboGM L92/LS3, bored 0.010 / Eagle forged 4.00-in
Bore/Stroke Ratio1.02: 1
Rod/Stroke Ratio1.53: 1
Bottom End
Block Description’07 + GM aluminum L92/LS3
Deck Height9.238-in
CrankEagle forged LS1, 4.00-in stroke
BalancerPowerbond SFI-approved
RodsEagle forged H-beam
Rod Length6.125-in
BearingsACL main and rod, Durabond cam
PistonsDiamond Racing forged aluminum
Piston-to-Deck Height+0.005-in
Piston PinsDiamond Racing, Trend Performance
Method Used to Retain Piston Pins in PistonsDouble Spirolox
RingsTotal Seal, 1.5/1.5/3.0mm, plasma-moly top, Napier second
PreparationFiled-to-fit, top, 0.021-in, second 0.023-in
Rod Bolts/Head BoltsARP 2000 rod, ARP head
Balancing Specs1,811 grams
Oiling System
Windage TrayGM LS1
Oil PanGM ’98-’02 F-body
Oil PumpGM LS6
PreparationTSP ported
Heads
Casting Number199-PRCL92
ChamberOpen
Head ModsFull CNC porting, five-angle CNC valve-job, clean-up milling, PRC dual valvespring kit with titanium retainers rated to 0.660-in valve lift
Combustion-Chamber Volume70cc
Maximum Flow at 28 Inches of Pressure356/237 cfm at 0.650 lift
Compression Ratio 11.1:1
Valves2.165/1.590-in
Angles Used in Valve JobProprietary, five-angle CNC
RetainersPRC titanium
KeepersFactory GM
ValveguidesFactory GM
Valve SealsViton
Rocker HardwareFactory GM
Rocker ArmsFactory GM, 1.7:1
PushrodsTSP chromemoly, 5/16-in
Length7.40-in
Cam
BrandComp Cams hydraulic roller
Duration at 0.050251/259-deg
Lift0.660/0.663-in
Centerline108-deg
Lobe Separation Angle111-deg
Installed Position108-deg
LiftersGM LS7 roller
ValvespringsPrecision Race Components, dual
Seat Pressure140-lbs
Open Pressure405-lbs
Timing ChainGM LS2 single-roller
Induction
Intake ManifoldGM L76
Throttle BodyP.T.M. 92mm
Fuel RailsGM L76
Fuel InjectorsGM factory Delphi 39 lb-hr
MAFTSP 100mm
Ignition
Engine ControllerGM LS1
Tuning SoftwareHP Tuners VCM Suite
CoilGM LS1 coil-on-plug
WiresMSD 8.5mm Superconductor Plugs NGK TR-6
Total Timing28-deg
Exhaust
HeadersKooks 1.875-in to 2-in stepped
Collectors3-in
Gaskets
BrandGM, MLS

Conclusion
The latest Gen IV offerings from GM are potent performers in stock form, and when you build a bullet-proof short-block and then enhance the excellent flow of the stock L92/LS3 heads with top-notch porting and a rowdy cam, they offer phenomenal horsepower and torque output.

According to Trevor Doelling, "The redesign of the Gen IV block from the LS2 into the larger bore L92/LS3 not only increased the cubic inches of the engine, but allowed builders to offer stroker engine packages up to 427 ci without resorting to expensive cylinder liners and machine work. It's now possible to sell a top-quality 418ci or 427ci short-block or long-block at a budget price. We work with customers on a daily basis to build L92/LS3 packages that will offer over 500 hp with a mild cam and close to 675 hp for naturally aspirated race applications.

"For owners looking to make even more power, both engines are rated to take up to a 200-shot of nitrous, but we recommend a 418 over the 427 in those instances.

Since custom pistons are available to vary the stock compression from 11.1:1 down into boost friendly ratios of 8.5:1, a forced induction 418 engine can achieve over 1,000 hp. In fact, our twin-turbo street car was built for high-boost, and other than the camshaft and dished pistons, uses all of the same components as this build. If the L92/LS3 can live under the big boost and heavy boot of Jason Mangum to the tune of 1,063 rear-wheel horsepower, it shows just how robust this package is."

Whether you're looking for a race-oriented long-block for your street and strip Firebird or GTO, or simply a set of excellent flowing heads for your next project, TSP has you covered with an affordable alternative to the LS7

SOURCE
Texas Speed & Performance
329 East HWY 62/82, Dept. GMHTP
Wolfforth
TX  79382
Sunset Racecraft
806-747-2700
www.sunsetracecraft.com
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