This is a disassembled 4.0 liter Porsche 997 GT3 flat-six engine in largely complete condition, with the key parts having been restored or refurbished ready for assembly.
The engine part include a Mezger engine case, barrels, heads, connecting rods, pistons, cams, valves, crankshaft, oil pump, timing chains, chain guides, a standard and fluid-damper front pulley, Wrightwood Racing gaskets, exhaust headers, and quite a bit more.
The 911 GT3 RS 4.0 is now widely considered to be one of the most desirable GT3 variants ever made. Image courtesy of Porsche.
History Speedrun: The Porsche 997 GT3 Flat-Six
The 4.0 liter flat-six fitted to the 2011 Porsche 911 GT3 RS 4.0 (Type 997) would be the final and most powerful version of the engine architecture that Porsche enthusiasts commonly refer to as the “Mezger” flat-six, named after legendary Porsche engineer Hans Mezger.
At the time of its launch, it was the largest-displacement and most powerful naturally aspirated flat-six ever fitted to a production 911, a distinction it held until later 992-generation GT3 variants surpassed its output.
This engine’s lineage can be followed back through decades of Porsche motorsport and production car engines. Hans Mezger was the lead designer of the original six-cylinder boxer engine for the Porsche 901/911 in 1963, and he went on to develop the engines for the Le Mans-winning 917, the dominant 935 and 936 endurance racers, the Group C-era 956 and 962, and the TAG Turbo Formula 1 engine that won three consecutive drivers’ world championships in the mid-1980s.
When Porsche needed a high-performance engine for its GT road cars in the late 1990s, it turned to the race-proven Mezger architecture, an engine derived from the power unit used in the Le Mans-winning 911 GT1-98, itself descended from the 959’s water-cooled-cylinder-head design. It was decided to base the engine design on this, rather than on the initially troublesome M96 engine used in standard 996 models.
The water-cooled Mezger engine made its debut in the 1999 Porsche 996 GT3, producing 355 bhp from a 3.6 liter displacement, and it was subsequently used in every GT3, GT3 RS, GT2, and GT2 RS variant of both the 996 and 997 generations.
This is a disassembled 4.0 liter Mezger flat-six engine from a Porsche 997 GT3. The Mezger engine case has been inspected, tumbled, and machined to accept Wrightwood Racing 105.4 mm piston sleeves, which together with a 76.4 mm stroke crankshaft for a total displacement of 4.0 liters.
The 997-generation GT3 saw the Mezger engine evolve in three major steps. The first was the 997.1 GT3 (debuting in 2006) which used a 3.6 liter version producing 409 bhp at 7,600 rpm with a redline of 8,400 rpm.
The 997.2 GT3 (debuting in 2009) grew to 3.8 liters and 429 bhp, while the 997.2 GT3 RS managed to extract 444 bhp from the same displacement. The RS 4.0 was the culmination of the series, though it wasn’t originally part of Porsche’s production plan.
According to Andreas Preuninger, the Director Porsche GT Model Line, the idea emerged after his engineering team proved the 4.0 liter GT3 RSR race engine was reliable in competition, and they proposed a limited-edition road car as a final send-off for the best-selling 997 generation.
The displacement increase from 3.8 to 4.0 liters was managed by increasing the stroke from 76.4 mm to 80.4 mm while keeping the original 102.7 mm bore. The longer stroke was made possible by fitting the crankshaft taken directly and without modification from the 911 GT3 RSR race car, paired with shortened titanium connecting rods and forged pistons.
The intake system was completely redesigned from the air intake all the way to the combustion chambers, after engineers discovered the 3.8 liter system’s airflow reached a ceiling at around 475 bhp. The compression ratio was set at 12.6:1.
The result was 493 bhp at 8,250 rpm and 339 lb ft of torque at 5,750 rpm, with a redline of 8,500 rpm and a specific output of 123 bhp per liter. The engine kept the Mezger architecture’s hallmark dry-sump lubrication, double overhead cams, four valves per cylinder, and “VarioCam” variable valve timing on both inlet and outlet valves. It was mated exclusively to a six-speed manual gearbox – this was an engine intended for true enthusiasts only.
Additional parts included in the collection are a gear-driven oil pump that has been disassembled and inspected, timing chains and guides, pistons, long-tube exhaust headers, Wrightwood Racing gaskets, and both a standard and fluid-damper front pulley.
Just 600 examples of the GT3 RS 4.0 were ever made. It was the last naturally aspirated Porsche to be powered by a Mezger engine, and the last GT3 RS offered solely with a manual transmission and without electric power steering.
It was the end of an era of analog, mechanical Porsche GT cars whose engineering family tree stretched back, however tenuously, to Mezger’s original 911 engine of 1963.
The Porsche 997 GT3 Engine Project Shown Here
This is a disassembled 4.0 liter Mezger flat-six engine from a Porsche 997 GT3. The Mezger engine case has been inspected, tumbled, and machined to accept Wrightwood Racing 105.4 mm piston sleeves, which together with a 76.4 mm stroke crankshaft for a total displacement of 4.0 liters.
The crankshaft is a standard-dimension 76.4 mm unit that has been magnafluxed, polished, and cross-drilled. It is paired with Pankl Racing titanium connecting rods that have been X-rayed and reconditioned with Wrightwood Racing Inconel 625 bolts and moly-coated GT3 bearings. The main bearings have been grooved and treated with a dry-film moly coating.
The camshafts and sprockets are stock 997 profile, and the cam followers are DLC-coated. The cylinder heads have had a valve job completed by S-Tec Motorsports of Stanton, California.
This is a disassembled 4.0 liter Porsche 997 GT3 flat-six engine in largely complete condition, with the key parts having been restored or refurbished ready for assembly.
Additional parts included in the collection are a gear-driven oil pump that has been disassembled and inspected, timing chains and guides, pistons, long-tube exhaust headers, Wrightwood Racing gaskets, and both a standard and fluid-damper front pulley.
The whole collection of parts are now being offered for sale out of Fallbrook, California on Bring a Trailer and you can visit the listing here if you’d like to read more about it or register to bid.
Images courtesy of Bring a Trailer + Porsche
Articles that Ben Branch has written have been covered on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, Autoweek Magazine, Wired Magazine, Autoblog, Gear Patrol, Jalopnik, The Verge, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with well over a million monthly readers from around the world and many hundreds of thousands of followers on social media.
