HMHaga - C5 Z06 nuts and bolts

I put the car on a weighing cell, measurement 1380 kg / 3042 lbs. The specified curb weight is 1440 kg / 3175 lbs. Ideally I should have weighed the car before I started to "add lightness". The weighing cell is calibrated annually, as it is used by the road authorities to verify compliance to regulations (e.g. total weight with a trailer).

“Adding power makes you faster on the straights; subtracting weight makes you faster everywhere" - Design philosphy of Colin Chapman, Lotus Cars. Why not apply it to the Z06? Adding power is expensive, removing weight is free. The air pump is not needed, the stock stereo is a disaster and the rear trunk looks almost as nice without the carpet. Trunk carpet removed Stock seats removed, the driver's side is replaced with a Sparco seat I put all the small parts in a bag to get the total weight Stock head unit, CD changer and speakers Secondary air injection pump and piping Power steering pump Fuel rail covers Air filter cover Rear trunk plastic covers Rear trunk lamps Tire puncture kit Weight of parts in bag 20 kg / 48 lbs Rear trunk carpet 6 kg / 13.2 lbs Rear trunk lid 2 kg / 4.4 lbs Floor mats 2 kg / 4.4 lbs Hood liner 1 kg / 2.2 lbs Passenger seat 14 kg / 31 lbs Driver seat 16 kg - Sparco Evo 12 kg = 4 kg / 8.8 lbs Total weight saving: 20 + 29 kg = 49 kg / 108 lbs  😎

The GM engineers allocated space for a starter battery in the trunk, but it remained in the engine bay until the release of the C6 Z06. I decided to replicate the setup as it improves the corner weight balance by shifting weight to the rear right wheel, which is the lightest corner of a stock C5. For the power cable, I used a heavy gauge 50 mm2/1 AWG multi stranded copper cable cable and press fit terminals. The heavy gauge is necessary to reduce the voltage drop caused by the long stretch and the high current required by the starter motor.  The ground cable is connected to the chassis, which is available in short distance from the battery inside the right wheel well. I installed a 350A automatic fuse next to the battery. The power cable is then routed forward above the right wheel well and then follows the existing wiring in the door sill to the front. With a battery in the passenger cabin it important to use a battery which does not emit harmful gases, so I used a sealed SMF battery.

Spring from an old welding cable, which helps to push up the boot lid when opened. 

The GM key fob has no tactile feedback, it reacts slowly and the rubber caps wear out. Fortunately, someone has reprogrammed VW key fobs to work with GM cars - and the Corvette C5. You have to cut the shaft of the stock key. Make sure that you don't cut too far down, otherwise the key will not fully enter the ignition lock - making it impossible to turn the key (BTDT). More information and links to e-bay on the Corvette Forums

Clutch pedal throw on the C5/Z06 is far too long. On track days, I can literally watch other cars gaining distance during a gear change. Trying to speed up the pedal movement only results in bad timing and loss of traction. Inspired by the thread at Team ZR1, I made a clutch pedal stop to reduce the throw length.  In most cars, the last part of the pedal travel is a waste, as the clutch is fully released with less movement of the slave cylinder.

Analog audio broadcast is history in Norway (replaced by DAB), and with a CD changer trying to play Johnny Cash and Mark Knopfler simultaneously, I was left with a useless head unit. No radio, no CD. I didn't want to spend too much money on an expensive and heavy 2 DIN unit and speakers, so the head unit is now replaced by an old Windows tablet and a single board 2x50W amplifier with bluetooth. The Bose door speaker units are replaced by two 6.5" speakers and new speaker cable wiring.  Total cost less than $150, with a "head unit" with much more capabilities than a traditional 2 DIN unit. I can install my own software and configure it completely to my liking, and even use it with HP Tuners to display engine management data. The new setup surprisingly plays with higher fidelity and more power than the Bose hardware.  As the head unit was replaced by a single board amplifier, I blocked off the location using plexiglass. When you paint plexiglass on the back side, it lo

Oily bottom end With an oil pan soaked in oil, it was time for repairs.  I had planned to replace the harmonic balancer with an ATI underdrive unit, but it was simply too expensive after adding shipping costs and 25% VAT. I decided on an OEM PB1117N Dayco balancer. Ouch, what a mess I found non-factory sealant between the front cover edge and the oil pan, so someone has previously serviced the engine. They obviously didn't care about centering the front cover and seal, which resulted in uneven wear of the seal, which again wore down the sealing surfaces of the harmonic balancer. To avoid a revisit later on, I decided to change all other parts that could be causing an oil or water leak in this area. Front cover gasket, water pump gaskets, front end seal. The lower oil pan gasket was changed last year. Removing and reinstalling harmonic balancer The first attempt at removing the balancer failed. I retried with a stronger puller with a sharp end tip, which would secure itself securely

First thing I did after purchasing the car, was to take it to a track day. When returning to the pit after the first session, there was power steering oil everywhere. The reservoir was filled to the correct level, but the heat caused the oil to expand and overflow. Home in the in garage, I found not only the power steering pump to be leaking oil, but all the lines AND the steering rack. I cleaned it up, replaced the old brittle return hoses to the oil cooler and refilled with Redline power steering oil. Next track day, the power steering was still leaking oil, but not to the same extent. I had also lowered the oil level to the bottom of the dipstick, to counteract the thermal expansion. The stock power steering pump is simply overwhelmed by the high RPMs, it builds too much heat and pressure and cavitates the oil. As I enjoy the thought of interfacing new electronics to the car, I decided to add an electric power steering pump to resolve the issue. After some research, I found that the

While changing the spark plugs, I was bothered by the secondary air injection pipes blocking access. Suddenly, the whole system was on the garage floor. This triggered multiple fault codes, giving me the perfect excuse to purchase HPTuners. Using HPTuners, the air pump activation was disabled and the associated fault codes disabled. Obviously, I couldn't stop there and spent a few hours researching what other settings I could tweak without affecting the fuel and ignition base maps. Disable all engine torque management/reduction and reduce traction control sensitivity Reduce sensitivity to IAT and ECT below 100 °C (don't retard timing) Disable CAGS/skip shift function Disable column lock failure speed limit Reduce the transmission temperature warning to 120 °C (the trans temp will then be shown in the DIC). Reduce cooling fan activation temperature, and also activate fans after ignition off Turn off AC compressor above 65% throttle Disable cat overtemp protection (there is no se

While changing valve springs, I noticed that the intake manifold was soaked in oil. This is due to the crankcase ventilation returning to the air intake.  Burning oil is bad for the engine, as it causes carbon buildup. Combined it can lead to pre-detonation (engine knock) on high load. I decided to add an oil catch tank to remedy the issue. Internet vendors charge stupid money for tin cans produced in China, so I usually design my own solution using the stock PCV and an aluminum bottle with steel wool to suspend and separate the oil vapor from the air. This time, I came up with the idea of using a water separator for compressed air, $25 in a hardware store.  The water separator contains a 5 micron filter to suspend the oil particles, and is rated for 1500 liters/minute. They are also designed to be easily drained. Perfect fit as an oil catch can. The only modification required is to remove and seal off the bottom spring loaded drain valve (I used a socket head bolt with an o-ring). Aft

With a Dremel tool and a throttle body in close proximity, the inevitable happened; the Dremel tool suddenly attacked the throttle body! As the aluminum dust cleared, I wondered if the throttle body would ever return to service. I clutched the ignition key and didn't let go as I turned it over, expecting the scarred throttle body to propel its engine to disastrous speeds. The engine, however, quickly settled to a calm idle. Now, the engine, the throttle body and its management system have formed a dream team. As soon as I apply throttle, the throttle body instantly feeds the engine with cold air, unlike earlier where it would consider my command for a tenth before executing. I intentionally left a coarse surface, as the physics says so. I didn't remove material close to the butterfly valve, to avoid issues with idle control. The air passage for the crankcase ventilation is a massive air block, so rebuilt the shape using chemical metal around a tube. Stock throttle body for refe

The LS1 came with the rear steam vent crossover pipe, but for the LS6 the GM engineers decided to drop the rear crossover pipe as it conflicted with the larger LS6 manifold. The ports are still in the LS6 engine block but they are simply blocked off. The rear steam vent supposedly help to avoid local hot spots in the rear cylinders, so while I had the manifold off to change the valve springs I decided to add the crossover pipe. I simply used the pipe from a truck, GM part 12605716. I only had to slightly bend the pipe to refit the LS6 manifold. I put a T-junction behind the manifold and then routed the house to the coolant expansion tank.

I came across a spreadsheet on corvetteforum.com with reported valve spring failures linked to the car build date. My 2003 with yellow valve springs was right in the sweet spot for a failure, which is not a good mix with track day usage and high RPMs. I decided to use the blue GM Performance valve springs, as I didn't (and don't) have any immediate plans for a cam upgrade. To prevent valves from dropping after removing the retainers, I coiled up a rope through the plug hole and then rotated each cylinder towards TDC. When the breaker bar resisted rotation, I knew that the rope was pushing on the valves. I then removed the retainers using a magnetic tool and a light tap with a plastic hammer.  While the valve springs are out, it would be dumb not to change the valve stem seals as well. The seals were easily removed using a plier, and I simply pushed the new seals on using a valve spring. I checked the valve gear for wear. The tappets looked almost like new, and I couldn't fi

With the intake manifold off, why not? I very much doubt the results of this dyno test (ref link below), but I've noticed that the engine is struggling high air intake temperatures on track days, so a thermal barrier between the hot engine and the intake manifold can't hurt. Link: Heatshield Products I-M Shield Install and Dyno Test: More Horsepower for Less

While disassembling parts of the dash and center console to repair the HVAC display, large pieces of brittle plastic disintegrated. To assemble the parts again, the plastic would need repairs.  Using a soldering iron, a Dremel tool and some leftover ABS plastic and zip ties as additional material, the cracked pieces were rebuilt.  The piece above the thermistor/air temperature sensor was broken off and missing, and was rebuilt by cutting out a similar profile from a piece of plastic. By melting deep into the original plastic piece, the new plastic bonds nicely.  Dremel tool and soldering iron used to repair the broken plastic pieces Repairs finished

The previous owner had installed Hurst shifter. It looked very nice, but ruined the gear shifts and produced a lot of noise. A loud metallic rattle that increased with engine revs. First, second and third try I made several attempts on quieting down the rattle caused by the Hurst shifter, and also to make the gear changes require less force. FatMat accoustic mat on the center tunnel Driveshaft rubber boot (the Hurst shifter makes away with the stock rubber boot) Anti-venom mod The gearbox has a detent ball spring assembly to provide artificial resistance when selecting a gear, partly also to prevent the gearbox to "pop out" of gear. By shimming the ball spring, the resistance is reduced) This helped to quiet down the noise somewhat, as the higher pitched metallic rattle was reduced. The effort to engage gears was reduced to an acceptable level by the anti-venom mod, but the cross gate movement was still too heavy due to the shorter throw of the Hurst shifter. Update! Don'

I didn't quite like the exhaust note with the stock h-pipe. The engine was throbbing and sounding like a motorboat on idle, and on engine braking it produced a metallic rattle. On wide open throttle, though, it sounded perfectly okay. A Borla x-pipe changed the exhaust note considerably, more of an exotic sports car sound at a higher frequency. This is due to the way the exhaust pulses are mixed with an x-pipe vs the h-pipe. In theory, the x-pipe should increase the exhaust flow due to better tuning of the exhaust pulses.

The stock corner lights were cracked and melted by the halogen bulbs. I replaced them with smoked corner lights and installed type 2 LEDs along with the required hyperflash relay. The type 2 LED has white illumination, but when the flash lights are activated the white LED turns completely off to give an orange flash only. The stock air intake mesh looks like a boy racer item, so I toned the appearance down by painting them black. From this To this