2006 Chevrolet Corvette Trick Flow Specialties Cylinder Heads Install - "Trick" Or Treat

A bit of clarification to Harland Sharp's installation instructions is in order. First, lifter preload must be checked. With both valves closed on cylinder 1 (remember we've left the crank at this cylinder's firing position), the rocker pair is installed and the bolts tightened just until each pushrod can no longer be jiggled or turned, representing zero lash. From this point, each bolt should turn within the range of 3/4 and 1 1/2 turns before reaching the final tightening torque of 22 ft-lb. We find that the intake takes 1 turn and the exhaust 1 1/4 turns, so we're OK and don't need different length pushrods. The rockers are then removed, their pushrod cups lubricated, and they're reinstalled. With cylinder 1 taken care of, we proceed along the firing order of the engine (1-8-7-2-6-5-4-3) 1/4 crank turn at a time, installing each rocker pair as we go. Also, Trick Flow's instructions state to use Teflon tape on the intake bolts, but we use threadlocker instead (this stuff usually seals well too). Here we install the rockers on cylinder 2.---->

With the rockers all on, it's...        read full caption With the rockers all on, it's reassembly time. We install the coolant temp sensor in the front of the driver-side head and the coolant plug in the rear of the passenger-side head, torquing to 15 ft-lb and being sure to use Teflon paste. We then proceed to replace all brackets, the power steering pump and its pulley, etc. etc.-all of this essentially reverse of disassembly, so we're not going to bore you with the details.	There is one part of the reinstallation...        read full caption There is one part of the reinstallation that requires special attention, and this involves the brakes. The steps outlined in the GM service manual for reconnecting the brake lines to the BPMV must be followed carefully. First, though, we clean the BPMV ports with a Q-tip, as despite extensive efforts to keep them clean while out of the car, they have grit in them (and probably did the moment the lines were disconnected). Then, after bolting the BPMV in place and connecting all six lines to their original locations, one must fill the reservoir and gravity bleed the master cylinder, as we'll see momentarily.	The intake manifold is installed,...        read full caption The intake manifold is installed, and its bolts get threadlocker. They are torqued in the GM-specified sequence to 44 and then the final 89 in-lb. For some reason, the front passenger-side bolt hits a brick wall 3/4 of the way down, so we use spacers in lieu of thread chasing (this likely was not the fault of Trick Flow but, rather, an issue with thread compound leftover on the bolt).
The valve covers go on without...        read full caption The valve covers go on without gaskets and the crank is spun two full revolutions so we can listen for interference with the rockers. Leaving the gaskets out helps compensate for the fact that hydraulic lifters are not pumped up when the engine isn't running (and thus full valve lift is not being achieved). When all's clear, the top of the engine is pre-lubed by squirting oil on all accessible surfaces, including the valve stems. Then the valve covers are installed (with gaskets this time) and torqued to 106 in-lb.	The headers bolt to the new...        read full caption The headers bolt to the new heads just fine, though our technique of leaving the X-pipe in requires someone to crawl under the car and push up to get them to line up. New GM bolts (PN 11518860, $3 each) are used in hopes of avoiding any disasters from old factory sealant buildup. Then the spark plugs go in, which is not a problem despite their having been relocated. Then it's fluid refill time: power steering, then coolant, then brakes. For the latter, the master cylinder is bled upstream of the BPMV by gravity bleeding from the front port as shown: have an assistant pump the brakes and then hold constant pressure on the pedal; open and close the port, and repeat a few times. The same is then done for the rear port on the master cylinder. Once this is complete, each wheel is bled in standard fashion. For this car, the order is: right rear, left front, left rear, right front.	The air intake goes on, as...        read full caption The air intake goes on, as well as everything else. Can't tell there are TFS heads on there, can you? Maybe we're throwing a pre-installation photo at you and you don't even know it? Nobody else will ever know, either-unless they look closely for the hard-to-spot "Trick Flow" and "225 CNC" etching in the engine bay!
The LS2 fires to life with...        read full caption The LS2 fires to life with no trouble at all, but we immediately notice a bit of a ticking noise, as if a lifter has not pumped up. A few brief restarts (letting the car sit a while in between) don't help, so I pull the driver-side valve cover and discover minor contact between the tip of the number 5 exhaust rocker and this nub on the underside of the cover. Some factory and aftermarket heads require a spacer to run roller rockers, but a quick grind and we're good to go, and damage to the rocker is happily only cosmetic.	Time to hit the dyno at TTP....        read full caption Time to hit the dyno at TTP. Matt Sorian is on tuning duty as always, and finds the same false knock situation we had during the baseline dyno pull (recall our discussion of this in "Solely Stainless, Totally Tubular," May 2007). Three degrees or so is being pulled out on tip-in, with a full 5.5 degrees of retard at full-throttle, high-rpm operation. (This is substantial enough that the tune is being kicked into low octane table, and Matt says we're seeing about 14-16 total timing; again, this is the same scenario as before installing the heads, so we're still drawing an apples-to-apples comparison). For consistency and accurate evaluation of the increase attributable to the GenX heads, the only adjustments made to the tune are to achieve an air-fuel ratio the same as during the baseline (12.9-13.0:1).	Our dyno graph shows a peak-to-peak...        read full caption Our dyno graph shows a peak-to-peak increase of almost 26 rwhp and over 15 lb-ft, with no loss anywhere. You can see the increase gets the most dramatic after 4,000 rpm. This is darn good, considering that the LS2/LS6 represents the pinnacle of factory cathedral-port heads-and that we're still sucking through the lackluster factory LS2 intake. After the dyno pulls, Sorian also does a part throttle tune to zero out the long-term fuel trims to keep them within +/- 4 percent. (This was never done after our header install, as software capability was not yet available for the new E38 ECM GM began using during the 2006 model year, so it's been a long time coming.)