z06vette.no

 A new track day, where I could have fun on the track without worrying about the health of the car. A new engine oil cooler kept the oil temperatures down while a vacuum bleed and fluid change of the clutch slave- and master cylinder solved gear change issues on high RPMs. View from Nissan R32

On the first track day with the Z06, the clutch pedal stuck to the floor as I shifted at high RPM. Imagine my surprise and disappointment. I could pull the clutch pedal up and continue, but it would repeat itself at intervals. I tried the "ranger method" numerous times to bleed the slave cylinder, but it didn't help.  I was about to start pulling down the exhaust etc. to access the bleed screw and purchase a Tick Master Cylinder, but then I found this thread: Clutch bleeding from the mc I figured I should give it a try: I drained and cleaned the reservoir and refilled it with new high temp brake fluid (Castrol React Performance DOT 4). I then applied vacuum to the master cylinder port using a MityVac. As can be seen, a lot of air pockets and old fluid was released. The vacuum makes the slave cylinder collapse, which squeeze out more of the old fluid than when using the ranger method. New fluid is sucked in by the reminding vacuum when the MityVac is removed. I repeated th

During the previous track day at  Vålerbanen in July 2020 , I had to run the engine at maximum of  5500-6000 rpm to keep the oil temperature below 140 °C if the session lasted more than 10 minutes. The C5 Z06 does not come from the factory with an oil cooler, but it is clearly required to avoid overheating the engine.  The stock temperature sensor is M12x1.5 while the oil cooler block is 1/8 NPT. I decided to drill and tap the correct M12x1.5 thread, which worked out nicely. I thoroughly cleaned out debris using brake cleaner and compressed air.  Oil cooler brackets being made Finished brackets New oil cooler block installed. The part of the hoses passing by the exhaust manifold are protected by additional heat insulation. This block  has no thermostat, as I simply cover the oil cooler with a sheet metal plate when not doing track days. A thermostat also restricts the oil flow, by the nature of its design. Oil cooler installed. I decided it had to be installed in front of the radiators

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.

The boot lid clicks open with a button, but annoyingly enough it does not raise high enough to slide a in a hand. Eventually, the paint wears away as you grab one of the corners to raise it. I installed a spring from an old welding cable, which helps to push the lid further up when opened. Problem solved! Cost $0.

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 stock key in half. 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

Almost the first thing I did after buying the Corvette was to participate on 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 everything, replaced the old brittle return hoses to the oil cooler and refilled with Redline power steering oil - this time only up to the bottom of the dipstick, to allow capacity for the fluid to expand. Next track day, the power steering was still leaking oil. 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 TRW/Vauxhall A

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 HP Tuners. Using HP Tuners, the air pump activation was disabled and the associated fault codes disabled. Obviously, I couldn't stop there and I've now spent quite 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 over temp pro

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 (although at a much higher pressure). 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 valv

"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" I intentionally left a rough surface, as the physics says so. To avoid issues with idle control, I made sure not to remove material too close to the butterfly valve. The air passage for the crankcase ventilation is a massive air block, I shaped it more aerodynamic using chemical metal.  After taking the picture, I decided to also bypass the coolant loop, so I cut off the coolant hose connectors. The coolant loop is to prevent the butterfly valve from freezing in cold weather, but even a WRX driven in -35 degC didn't have issues with a coolant loop

The rear crossover pipe/steam vent reduces local hot spots in the rear cylinders by allowing air and steam to escape. The LS1 came with the crossover pipe, but was removed for the LS6 as it came in conflict with the larger intake manifold. The ports are still in the LS6 engine block but they are blocked off.  . When 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 on a T-junction and routed the hose back 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 don't have any immediate plans for a cam upgrade. To prevent valves from dropping after removing the retainers, I coil up a rope through the plug hole and then rotate each cylinder towards TDC. When the breaker bar resisted rotation, I know that the rope is pushing on the valves. I then remove 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 are easily removed using a plier, and I simply push 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 find any valve guide wear/p

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