Porsche 911 GT3RS 4.2L Pumpkin Build

Happy Halloween! When better than today to post a story about an orange, pumpkin-looking Porsche 997 GT3RS being built into a 4.2 liter track monster? Champion Motorsports in Florida is the shop who is responsible for this track day build thread, who you may remember from a feature we did not long ago about a Turbo S being transformed into the ultimate RSR street/track car. They have done quite a few 997 Turbo engine builds, but this time they have turned their attention to a naturally aspirated GT3RS owned by 6speedonline.com forum member “Ranger”. We wouldn’t be surprised to see this brute savage overtaking Cup cars on the straights like a possessed pumpkin as it’s sound alone is unbelievable, if nothing else. Trick-or-treaters will be scouring for cover when they hear this evil jack-o-lantern come-to-life barreling towards them, taking shelter and ducking into any shallow hallow near by in fear of what lurks in the deep recesses of it’s darkened heart…
Ok ok, not to worry, that will be our last and only attempt at Halloween humor so please continue on the next page without concern to cheesy amusement, we promise…
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This particular GT3RS is a bit more of a full track oriented build than our last feature by Champion, and has their complete line of CMS suspension components. They have posted it’s full build thread along with another thread that just features just it’s engine build, both linked at the bottom of this page.
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To start the journey,they began by taking a dyno run with the 3.8 liter engine before disassembling it to get a baseline to compare the horsepower with once completed as a fully built 4.2. It pulled 396 hp to the wheels consistently after several runs.
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Their next focus was on weight reduction, which included purchase and installation of Porsche Motorsport lexan windows, replacing the seats with some Recaro’s and removing 19 pounds of padding from under the carpet.
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996 Cup car shifter cables from Porsche Motorsport were next on the list of improvements, along with a custom gear set from Guard Transmission featuring lightened and hardened gears as well as a 60/40 LSD and custom 4 way adjustable front and 2 way rear Ohlins coilovers.
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Rather than just read off a list of parts, how about a video to set things straight? Here it is what 512 hp at VIR looks and sounds like. We suggest that you start listening at it winding out at about 4:15, it’s absolutely mind boggling. How dare it:
The car’s owner, “Ranger” on 6speedonline.com is a well known member in their community who contributes frequently. Now with his 4.2 with bored, stroked, built heads, full case work, new crank, etc etc, would you wager that he has more friends now, or possibly enemies?…
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Link to our Champion 911 Turbo S/RSR feature story here: 

 

 

4.2 LITER ENGINE DETAILS:
  • Custom built Mahle pistons with specially tailored valve reliefs. Pistons also have a hard anodized coating on the crowns for heat rejection, as well as an anti-friction coating on the skirts. The bore is 105.9mm, and we’ve used specially made iron liners for this application.
  • The cylinder water jackets have been CNC machined to not only accept the 105.9mm liners, but also to keep the distance between the water jacket and the liner consistent with the OEM Porsche clearance in order to keep water flow in this area optimal.
  • The crankshaft was built with a stroke of 79mm. This combination yields a final displacement of about 4.145cc. We’ve got a future build planned with an 81mm stroke, but this particular engine uses the 79mm stroke. (Before anyone asks….the answer is no. We will not be giving out any details about our crankshaft other then what I just mentioned. It took an UNBELIEVABLE amount of work to develop this crankshaft, and to be perfectly honest, it’s not information we want to share with every other engine builder out there. All of the details are documented and explained to customers who have a build done by us.)
  • Compression ratio of this engine was set at 13:1. Since it will primarily see only track usage, the benefit of using race fuel at this higher compression will result in higher output. The customized GIAC programming will also have a safe pump gas mode.
  • Connecting rods are very custom built Carrillo rods, using proprietary rod bearing diameters. The bearing is a tri-metal construction and is individually sized to each crankshaft journal after an anti-friction coating is applied. In a situation of a missed shift, over-rev, or improper oil fill, this coating may just save the engine in the unlikely event of contact between the bearing and the crankshaft.
  • Each engine case is also custom machined to optimized case windage. All of the areas around the webbing and crankshaft are all relieved by machining to maximize air flow and minimize restriction. This is a VERY tedious process, but makes for a much smoother running engine and a few extra HP too.
  • The oiling system has also been internally modified. Cross drillings in the crankshaft and engine cases are modified to redirect the flow of pressurized oil most for sustained high RPM use.
  • Cylinder heads received a full race treatment. In addition to a multi-angle competition valve job, we also use slightly oversized valves on this engine. We used hi-rev valve springs, as well as super lightweight titanium spring retainers. We also did a complete port, polish, and flow bench port balance on the cylinder ports.
  • Keeping the heads in place are some serious head studs. We use an aerospace quality head stud that takes the thread engagement from 10mm in diameter and 25mm in depth, up to 12mm in diameter and 40mm in depth. We then choose an appropriate thickness for the head gasket and rather then use a standard sealing ring, we use a gas-filled ring is used between the head and the cylinder bore. This seal is basically impenetrable.
  • Lastly any engine we build like this will receive a full balance as well as documentation of measurement (“blueprinting”). All of internal components of the engine are “zero balanced” which allows the customer to change a flywheel or pulley at a later date.

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