You haven't seen our 2006 Corvette project car since summer 2007, and we admit, that's a long time. (More than enough time, even, for some readers to have gone from bachelorhood bliss to diaper duty.) We have no excuse, really; but we will say we've had a more-than-sufficient opportunity to mull over just how to crown this story series.
Our express purpose from day one has been to try and duplicate Z06 performance for a fraction of the price. In this, our final installment, we'll perform our last set of mods and hit the dyno to see just how close we got. But before getting into all that, we do have one piece of unfinished business to mention, and that is regarding the aftermarket clutch we installed back in our penultimate segment ("Preemptive Strike," August 2007). As it turns out, our SPEC Super Twin exhibited excellent streetability. We found nothing but smooth engagement during the great majority of starts, and even when it did show up once in a while, clutch chatter was quite livable, especially for a clutch with a 900 lb-ft capacity. We should point out that, again, we installed SPEC's entry-level Super Twin, which features its least-aggressive friction compound; we'd imagine SPEC's higher-horsepower materials would probably be a little grabbier. We also noticed the shifter glides through the gears with less effort, reportedly a result of more complete clutch disengagement. One aspect of this clutch system that took a little getting used to is that the pedal grabs a bit higher than stock and has a somewhat shorter range of engagement-but SPEC says this is fully intentional, to enable quicker shifts. Probably the only real downside to this clutch system-and one that has nothing to do with performance or driveability-is that there is some additional gear rattle in neutral with the clutch out, which according to SPEC is a result of having two disc plates, each with a higher clutch disc damper spring rate.
'Nuff said on that, so back to the case at hand. We've stated all along that we were planning on keeping this project naturally aspirated, and are sticking to that promise. With our C6's LS2 bone-stock from the coil packs down, this made the next obvious choice from a power perspective a head/cam package. But we decided to do things a little differently so as to both maintain stock-like driveability and to keep options open for forced induction further down the road. Therefore, we're opting to leave the stock cam in place and forgo having to put in a bumpstick that would be a compromise between N/A and boosted power. So although ponies will be left on the table with a head-only swap, it leaves the project more open-ended for the purpose of future upgrades, among other things (e.g., idle quality, less attention from the boys and girls in blue, et cetera).
Trick Flow Specialties, a proven name in LS performance, supplied us with a set of its GenX Street/Strip CNC-Ported Cylinder Heads. While there's a handful of cylinder head types TFS offers for LS engines, we're using the LS2 version of the head, which has 225cc intake ports, 65cc combustion chambers, and 2.055-inch intake/1.575-inch exhaust valves. (LS1 versions, for example, feature a 215cc intake port along with slightly smaller combustion chambers and intake valves.) There's a ton of technology in these TFS heads: they feature 5-axis fadal machined combustion chambers, and intake and exhaust ports with minimal machining stepover for max flow. The valve jobs are done using high quality Serdi machining centers for high concentricity from the valve to the valve seat, less runout, and a longer lasting valve job.
High-quality Ferrea stainless steel valves, ductile iron valve seats, high quality double valvesprings good for up to 0.600 lift, bronze alloy valve guides, and Viton seals round out the package.
Our complete "head package" for the project. The main items, of course, are Trick Flow's GenX Street/Strip CNC-Ported Cylinder Heads in 225cc form, fully assembled with valvesprings good to 0.600-inch lift (PN TFS-3060T001-C02, $2,395). Also shown is our set of TFS chrome-moly pushrods (PN TFS-21407500, $86), as well as Harland Sharp roller rockers (PN CSP-SLS17, $399), ARP Pro Series head bolts (PN ARP-134-3610, $111), and GM MLS head gaskets (2 x PN NAL-12589227, $90 for the pair).---->
In its current form, our LS2 puts 376.8 hp to the tires, benefiting solely from an aftermarket air intake and throttle-body spacer, headers, and a cat-back. And while its LS2/LS6 heads aren't a bad factory piece, they've seen their last days under this Vette's hood.---->
First order of business: disconnect the battery ground, then take off the engine covers and remove the induction system forward of the throttle body (in our case, this consists of a VaraRam ram air kit-see "Ethereal Rush," March 2007). The throttle body can stay on the intake.---->