Installation Tech: Longtube Headers on C6 Corvette
Posted at 2:44 PM / June 26, 2009
Some people are happy and content keeping things in their original equipment form as delivered; computers, mobile phones, XBox's, and most commonly vehicles. Then there are those that cannot leave anything on these devices alone, we commonly hear of these people tweaking their electronic devices to do new and fascinating things. With vehicles it is a little different as usually physical work is involved and higher costs incurred compared to a $200 mobile phone, but the end result is the same; the satisfaction of knowing you now have something better than the next guy who didn't mod their vehicle. Don't bother explaining this to your wife or your Prius loving coworkers, it takes a "modder-at-heart" to really understand the motivation and drive behind our thinking. Our topic of installation with this go-around is headers. Follow along as we perform a header swap with before and after dyno results on a 2007 Corvette C6.
Late model C5 and C6 Corvettes are stout performers in OEM form, but what happens when you tire of that as-delivered performance? What can be easily be accomplished by getting your hands a little dirty on a weekend afternoon with a few hand tools and a few buddies to drink your beverages? There are a list of bolt-on items that all add a little horsepower here and there; from air induction to supercharger kits. Without even going into your engine, there is a slew of things you can do to increase power and sometimes engine efficiency. Headers are one such mod.
This 2007 C6 is virtually untouched until today, a trait common to the majority of C5/C6's on the road. Headers are one of the mods you can accomplish that has no detriment to actual vehicle drivability, which is important to many Corvette owners. Basically you are adding power by uncorking restrictions in the OEM exhaust and allowing a smoother transition in exhaust gas flow pulses, as the simple function description. There are other benefits such as increased fuel economy and a louder exhaust note if catalytic converters end up missing. (Which is for off-road use only FYI!)
Don't be intimidated by the outward high-tech appearance of the Corvette, on the inside it is still a blood-and-guts engine held together with bolts, like any other. If you have a basic metric tool set, a jack and 4 jackstands, there is nothing hard about doing a header installation on these cars other than "mod anticipation", luckily with this particular mod, the timeline is short.
Tools Required
• 10mm Wrench and Socket
• 11mm Socket - if necessary to remove steering shaft
• 13mm Wrench and Socket
• 15mm Wrench and Socket
• 3/8" Drive Ratchet and Extensions or Air Ratchet - if available
• 5/8" Spark Plug Socket
• 7/8" Oxygen Sensor Socket
• Small Pocket Screwdriver to Remove Electrical Connectors
Parts Required
• C6 Header Kit (Using TSP 1-7/8" C6 Headers in images)
• X-Pipe kit to connect headers to Catback System
• Front oxygen sensor extension harnesses (x2)
• Rear oxygen sensor extension harnesses (x2, if cats retained)
• New header bolts or exhaust gaskets (optional)
• Regular Price: $829.99 regular price in full kit form (Off-road System)
• Price as-tested: $769.99 on sale in full kit form (Off-road System)
The Installation
1. As with all vehicle installation projects, the first step is to remove the negative battery cable from the battery. This is a safety move that alleviates shorting out metallic objects on either the starter or alternator connections. Both the engine dipstick tube assembly and exhaust manifold gasket are common items to short out if the battery was not disconnected.
2. Remove both "Corvette" engine covers, taking care not to crack the drivers side cover where it has to be manipulated over the braided engine fuel supply line.
3. Remove the main accessory drive belt via the 15mm sized tensioner, note the belt routing if your diagram is missing. Disconnect the O2 Sensor connector, the LS2 connector is located in the lower-middle of the coil pack rail. You will need a small screwdriver to unlock the harness retainer once unplugged. Remove the Alternator held on with (2) 15mm headed bolts.
4. Optionally, the engine coil packs can be removed for greater access to manifold bolts if desired, C6's have generous room due to coil packs that are moved higher on the valve cover and due to the lack of AIR injection tubes the prior C5's are equipped with. The coil pack rails are held on by (5) 10mm bolts on each valve cover. Disconnect the (8) spark plug wires from coils before removing.
5. Remove the (8) spark plugs with your spark plug socket and a short extension. Remove the engine dipstick tube via a single 15mm headed bolt and note the routing of the dipstick tube. These are sometimes a bear to dislodge out of the block, but back and forth motions while pulling upwards tend to disrupt the o-ring seals grip in the block.
6. The Corvette will need to be on jackstands or a vehicle lift from here. Use (4) jackstands preferably on the aluminum front and rear suspension, or if using a lift use lifting "pucks" or spacers on the steel frame rails access spots; located under the front and rear of each door.
7. The use of WD-40 or your favorite rust penetrant is recommended on all exhaust bolts that need to be removed. Exhaust bolts are a magnet for rust. Letting the lubricant soak for a few minutes before removal helps out immensely. These bolts are the (4) "manifold to cat" studs, the (4) "cat to h-pipe studs", and the (2) "h-pipe to catback clamps", a small amount on the O2 sensors will also help later.
8. While allowing the bolts to soak, you can reach up and disconnect the (2) rear O2 sensor connections, you may need a long flattip screwdriver or some small feminine hands to finess the connectors apart. If these are too hard to disconnect at this point, you can remove the O2 sensor from the exhaust and let it dangle until more room is acquired later on.
9. Remove the (4) flange nuts at the front of the factory H-pipe using a 15mm deep socket and ratchet, then loosen the (2) band clamp nuts at the rear of the H-pipe. Once loosened you may remove the (2) 13mm hanger nuts located at the rear near the transmission. These will be reused on the new hangers. When everything is loosened, you can finess the OEM H-pipe out of place, starting by removing the front first and sliding the H-pipe forward off the catback slip connections. You may need the help of a buddy if these are uncooperative.
10. Once the OEM H-pipe is separated from the car, we turn our attention to the catalytic converters. These are removed with (2) 15mm studs on each flange. You will need to use a longer extension and possibly a breaker bar to initially break the nuts loose. I use a 3/8" impact gun, to help speed things up. Once loose, they both easily are removed from the bottom of the car.
11. All that should be left now is the small exhaust manifolds themselves. On the C6 these are held onto the engine with (6) 13mm bolts on each manifold. Remove the (6) exhaust bolts and the manifold will pretty much fall out of place, removal is easiest from under the car although through the top is possible also.
12. Now the entire OEM exhaust is removed save for the catback, if reused. Now is a good time to install the O2 extensions, route these away from moving parts, hot exhaust and sharp edges or the block. Use plastic zip ties to keep these in place. Zip tie harness to brake booster vacuum line, and the brake lines on the drivers side. On the passenger side the large battery cables and the electrical harness that follows the torque tube make for easy harness routing.
13. The new headers will slip in from the bottom on C6 Corvettes, some manipulating of wiring may be needed to get the headers into place, but otherwise they slip in easily. Install one side at a time with the gaskets and leave the header bolts snug but not tight until the full exhaust is in place. Slip-fit exhaust systems do not every exactly line up the same every time, leaving the exhaust "loose" helps align the new x-pipe next.
14. After the headers are in place, install and connect the front O2 sensors to the extension harnesses. I drilled an additional 1/4" hole in each side of the support plate near the O2 sensor location to add an additional wire strap location. Route the rear O2 extensions along the tunnel plate, adding wire ties or wire clamps as needed to secure.
15. The TSP C6 headers use staggered length collectors to allow easier X-pipe installation, align the left side first, then align the right side and slip into place. Slide on the included exhaust band clamps and snug up the bolts. Install the (2) 13mm hanger nuts to help support the weight of the exhaust. Once the X is installed, the header bolts can be tightened down further. The torque specification is 15 lb feet, although more wouldn't hurt, I often use 22 lb feet with headers.
16. Install the rear portion of the X-pipe to connect the X-portion to the catback. This is a little tricky with the catback in place, enough room is include to slide these extensions a good portion over the X-pipe, twist and slide these in as far as they will go either before or after X-pipe installation. Then slide rearwards to meet and install over the catback slip fit, rotating for best alignment.
17. Install the remaining clamps, align the X-pipe centering it under the body while keeping exhaust tips aligned, then tighten down all the clamps, recheck the alignment of the system after tightening the clamps down once more. It is common for all C5/C6 exhaust systems to settle in after a few hours of driving, the exhaust tips may need once more alignment after an exhaust heat cycle.
18. Going back top side of the engine bay, reinstall the spark plugs, spark plug wires and coil packs and all disconnected wiring. Install the dipstick tube and check to see if the mounting flange clears the exhaust header primary flange, it often needs to be trimmed or spacered out away from the header as clearance dictates. If so a longer bolt and a small spacer may need to be installed if trimming the dipstick bracket is insufficient.
19. Once the ignition system is back into place, reinstall the alternator and belt. Then reinstall the two plastic engine covers back into place. Go back over the entire exhaust system to make sure nothing rubs the exhaust and no wiring is out of place. Sometimes the transmission cooler lines will need to be manipulated away from the exhaust on the passenger side. Reconnect the battery.
Now that the header install task is complete, you can start up your Corvette and make sure everything is ok (no melting wire, no exhaust leaks). If you removed any emissions devices, remember you will need PCM tuning to alleviate the check engine light from setting, if cats are retained there should be no codes. Don't be suprised at smelly exhaust and light smoke emitting from the exhaust on initial startup, it quickly will burn off. If everything is ok, you can put the car back on the ground and road test the car, enjoying your new-found power.
Typical gains of adding headers to LSX vehicles is usually in the 20-25 rwhp range and a little torque. The installation on this bone-stock car otherwise yielded 20 rwhp and 15 rwtq gains at peak, but if you look at the graph you will see the gains are across the board, this is a mod you can feel in the seat-of-your-pants before and after. The gains would have been slightly more had a good catback system been in place or installed along with the headers, but this is a good test result of just installing headers and matching X-pipe only. Further gains can be had by fine tuning the Air/Fuel Ratio and Timing curves to optimize each car.
Source: Texas Speed and Performance: www.Texas-Speed.com - Phone (806) 866-0734
