What's a photo of a boat doing in Corvette Fever? Taking you on a trip where you can catch a glimpse of the future. The boat in question is powered by a GM Vortec marine engine. Since 1958, GM has been supplying engines to a host of boat manufacturers. Marine engines are routinely subjected to considerably more severe operating conditions than their standard passenger-car counterparts, and that makes them ideally suited to high-performance applications.
That fact hasn't gone unnoticed by the staff of GM Performance Parts (GMPP). As a result, numerous engines that were originally developed for marine applications have turned up as crate engines in the Performance Parts catalog. (Which explains why some crate engines have surprisingly low compression ratios; most marine engines are designed to survive on a diet of 87- or 89-octane gas.)
This past summer, Tom Read of GM Powertrain Communications organized a preview of the latest marine engines being actively marketed under the Vortec brand name. At the time of the preview, no decisions had been made regarding the specific engines that will be offered by GMPP, but hopefully a few of the big-blocks and 6L, LS1-based offerings will make the cut. Both types of engines will be ideal for transplanting into a Corvette.
Currently, there are three...
Currently, there are three 8100 Series (496ci) Vortec marine engines, (derived from the fuel-injected 8.1L big-block used in Silverado pickups) identified as HP1, HP2, and HP3, and rated at 375, 420, and 525-plus horsepower respectively. The HP3 is especially impressive considering its 9.1:1 compression ratio and the minimal number of upgrades. CNC-ported cylinder heads, port-matched intake manifold, high-lift hydraulic roller cam, special valvesprings, aluminum roller rockers, machined-steel camshaft sprocket, windage tray, headers, and welded oil-pump pickup are the only major differences between the HP1 and HP3. Final horsepower and torque figures for the HP3 hadn't been decided upon at the time of the preview, but at 525 hp and 560 lb-ft of torque, the engine is clearly not at its full potential. Manifold pressure readings of an HP3 being run on the dyno at the GM Tech Center indicated the simple addition of a larger throttle body would put a nice bump in the power curve.
The 6L Vortec marine engines...
The 6L Vortec marine engines are also entirely suitable for placement between the fenders of a Corvette. The naturally aspirated model is essentially a "marinized" version of the engine that powers Chevy and GMC trucks and SUVs. In its marine form, it's rated at 350 hp, which is the minimum power rating it will carry if it hits the Performance Parts catalog. With a cam change and slightly more aggressive ignition timing, the engine will easily crank out 375-plus horsepower and yet be mild enough to deliver excellent low-speed driveability and fuel economy.
The engineers at Powertrain...
The engineers at Powertrain are also experimenting with a supercharged version of the 6L engine. At this point, the engine is still being tested and evaluated, so no horsepower numbers have been released. However, considering that the naturally aspirated version of the engine is rated at 350 hp, the supercharged edition should hit the charts at well over 400.One of the most compelling aspects of the Vortec marine engines is their durability. Before an engine is released for production, the combination must pass a 300-hour, wide-open-throttle durability test. Since all the major components are retained when a marine engine is packaged for sale through GM Performance Parts, "crate engines" offer this same level of durability. And that's just what every Corvette owner needs.