The GM LS3 crate motor is a proven starting point. At 494 hp and 491 lb-ft of torque in stock form, it delivers consistent, repeatable power. But for builders looking to push beyond the factory configuration, the LS3's architecture supports significant gains with the right combination of intake, cam, and cylinder heads.
This build documents that process, measured on the dyno from baseline to final configuration.
For dyno testing, the LS3 was equipped with 1 7/8-inch ARH headers, a Meziere electric water pump, and Lucas synthetic oil. A Holley HP management system and manual 90-mm Holley throttle body replaced the factory drive-by-wire setup.
As delivered from Gandrud Chevrolet, the stock LS3 produced 494 hp at 6,000 rpm and 491 lb-ft at 4,700 rpm. These numbers established the baseline for all subsequent modifications.
The Speedmaster Individual-Runner Intake
The Speedmaster IR intake brings an 8-stack, individual-runner configuration to the rec-port LS3 application (an LS7 version is also available). The complete system includes eight polished aluminum air stacks, individual intake runners and throttle blades, provisions for a TPS sensor on both ends of each throttle blade row, and a vacuum source on each runner for the MAP sensor. A common MAP signal from all eight runners provides more accurate readings than a single-runner source.
The downdraft configuration does add height, which limits hood clearance in low-profile applications such as the Camaro, Corvette, or GTO. The intake is better suited to muscle car swaps, truck builds, and street rod applications where vertical space is available.
Cam Upgrade: Crane Hydraulic Roller
Swapping the cam required removal of the factory damper and front cover. The factory LS3 single-bolt timing gear and cam were upgraded to a 3-bolt design.
A cam profile change is the single most effective performance upgrade on an LS platform. The Crane hydraulic roller cam selected for this build offered .600 lift on both intake and exhaust, a 232/240-degree duration split, and a 113-degree lobe separation angle. As with all stock LS applications, cam profile selection is constrained by available piston-to-valve clearance, since the factory pistons have no valve reliefs.
Cylinder Heads: Trick Flow Gen X 255
The factory heads were replaced with Trick Flow Specialties Gen X 255 CNC LS3 heads. These heads flow over 380 cfm, approximately 60 cfm more than stock, from intake ports measuring 255 cc versus the factory 260 cc. More airflow from a smaller port volume is a meaningful engineering outcome: it improves port velocity and mixture quality across the rpm range.
The Gen X 255 heads feature a dual valve-spring package with sufficient pressure and coil-bind clearance for the .600-lift Crane cam. Installation used Fel Pro MLS head gaskets and ARP head studs.
Using custom rocker stands supplied with the heads, the TFS Gen X 255 heads retained the factory LS3 rockers but required slightly longer pushrods (7.7 inches versus the factory 7.4 inches).
Final Assembly and Results
With the Speedmaster IR intake, Crane cam, and Trick Flow Gen X 255 heads installed on the otherwise stock LS3 short block, the engine returned to the dyno under the same timing and air/fuel parameters used during baseline testing.
The Speedmaster individual-runner intake features individual throttle bodies, radiused air horns, and billet fuel rails. Dyno testing showed it contributed as much as 30 hp over the factory intake.
The modified LS3 produced 605 hp at 6,800 rpm and 532 lb-ft of torque at 5,000 rpm, up from 494 hp and 491 lb-ft in stock form. Peak power moved higher in the rev range as expected, but the combination produced no penalty in low-speed torque. The Speedmaster, Trick Flow, and Crane combination outperformed the stock configuration from 3,000 rpm through redline.
Build Summary
Baseline (stock LS3): 494 hp at 6,000 rpm / 491 lb-ft at 4,700 rpm
Modified: 605 hp at 6,800 rpm / 532 lb-ft at 5,000 rpm
Gain: +111 hp / +41 lb-ft with no loss below 3,000 rpm
Sources
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