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Delay due to damaged clutch kit from Summit Racing

Guess what happens when a flywheel, a pressure plate and a clutch disk are free bounce around in a box across the Atlantic Ocean? I purchased a new LUK OEM clutch kit from Summit Racing. The clutch kits from LUK are sent in a cardboard box without any protection and everything inside is free to bounce around. Across the Atlantic Ocean, this is bound to go wrong. Nobody would cover the damage, as I used a forwarding courier to send the kit from the USA to Norway. Summit Racing also refused to send or sell me a new clutch disk. Sold separately it has the same price as a complete kit. Not the best customer service by Summit Racing, I have to say. So, to get my Corvette on the road again - I have to purchase a second clutch kit! "Insanity is doing the same thing over and over again and expecting different results", so I did not order another clutch kit from Summit Racing.  I was lucky to source a lightly used Spec stage 2 clutch kit from a nice fellow in Alabama, who sent the par

Built 4.10 rear differerential

Late April, and the spring finally arrived with temperatures making it possible to start on the pending repairs.  I started by draining the oil from the noisy rear differential. This is what the T-1000 Terminator is made of; liquid metal drained from a Getrag differential. A magnet picked up a lot of metal shavings.  The output shafts have significant play, which is an indication of worn clutch packs and belleville washers, and possibly broken output shaft stubs (I will find out when I disassemble the differential later). With all these issues, this differential needs a complete rebuild. It is hard to find specialists with the knowledge and the tools required to perform this work in Norway. The cost of shipping the differential to the USA and back for a rebuild is also excessive, due to the weight. So, the conclusion was to purchase a built 4.10 differential, which obviosly also gave the opportunity to change to a different gear ratio. Built 4.10 differential C6 Z06 output stub shafts

Waiting for spring...

24th of April. Winter has no plans to release its cold claws...

ICT billet ignition coil brackets

A V8 engine shouldn't be covered by plastics, so I removed the plastic valve covers. This only reveals a new layer of connectors and sheet metal brackets, this is clearly not an engine designed to be put on display. I replaced the sheet metal brackets with ICT billet ignition coil brackets, which helped somewhat (I also have to do something with the coil pack connectors). In hindsight, valve covers with integrated coil posts would have been even better.

End of 2022 season

Winter is coming The C5Z is in hibernation until spring time. I don't have a heated garage, so working on the car in freezing temperatures is not an option. At least I can start to make a plan for the next season. The car in front is an MB R350 with a stretched cam chain, lots of work to get that fixed on an OM642 engine. Drivetrain maintenance I returned from the last trackday with a load humming from the rear end of the C5Z, which is probably a differential failure. I'm hoping for a simple fix like broken belleville springs, draining the oil will give a telltale. There are already other issues that requires attention, so I guess the time has come to have it all sorted: Broken rear differential Engine rear oil seal leaks (which requires removing the torque tube anyhow) Worn slave cylinder ("clutch pedal stuck to the floor") Clutch and flywheel replacement Torque tube couplings and bearings

Larger 330 mm rear brakes from C6 Z51

Don't drive with your nannies on! With active handling in competitive driving mode, yaw control is still active and using the rear brakes to correct excessive yaw on corner entry/exit. This is not an issue on regular street driving, but on a racing circuit this continuous correction causes the rear brakes to overheat. In my case one of the rotors cracked as the car cooled down in the pit. I even heard the *PING* as it happened. 305 to 330 mm brake rotor After some research, I found that the C6 with the Z51 option code uses a larger 330 mm brake rotor, but still share the same caliper and parking brake dimensions! Plus Increased thermal capacity. The EBC Z51 rotors are ventilated on both sides, have a higher mass and increase the swept diameter of the brake pad Better looks, the brakes fill the 18" wheel and looks more in balance with the front big brake kit. Reuse of stock brake calipers and parking brakes Minus Change of brake brake bias. The increased rotor diameter causes a

Window regulator replacement

High up in the mountains in Norway, close to freezing temperatures, the driver side window regulator broke down. Perfect timing. Fortunately, I managed to pull the window up by assisting the motor. A broken piece of plastic was all it took I had to twist my brain to get the parts back in the correct orientation. Notice that as pictured, it will not work. The wire coming from left (door B pillar) needs to pass below the right wire, otherwise it will conflict with the window. Mounted incorrectly here: I also noticed that the regulator power cable and the door latch switch cables interfered with the mechanism as it moved up and down. so I used some high strength duct tape to move them out of the way. New window regulator in place. I ran the window all the way down so that there wasn't any tension on the mechanism before tightening the bottom nuts. I followed Chris Askew's guide to replace the regulator:

Trackspec T1 hood vent

Heat management is still an issue on track days, so I decided to add a Trackspec hood vent. Trackspec T1 hood vent Optimized louver design to maximize extraction flow velocities within a vehicle in motion Reduces under hood pressure delta to reduce front end lift and increase net vehicle downforce. Significantly reduces under hood temperatures by extracting heat and allowing fresh cold air to enter the engine bay. Maximize life of engine accessories by reducing overall operating temperature. Increases dense, cold air flow through radiator to promote lower coolant temperatures. -exactly what my C5Z needs! I managed to source a second hand T1 hood vent in good condition. For the install, I decided to use countersunk hex screws rather than pop rivets, as I don't like the look of pop rivets (it is not a kit car, after all). To countersunk a screw, you need enough material thickness for the screw head. I looked up some tables and concluded that M3 (3 mm) screws would work. An Ø6.3 mm 90

1000m runway drag

My first drive on a drag strip. Not really a drag strip, but a 2000 m long runway in the mountains in Dagali, Norway. We had the opportunity to use 1000 m, with ~500 m for braking. I failed completely on the first attempts. Too much adrenaline and wish to go fast, so the tires didn't hook before 3rd gear. I learned I had to drop the launch RPM down to almost idle and modulate the throttle to maintain traction. I guess it didn't help with 6 year old Kinforest 280 UTQC rear tires and an air temperature of only 5-6 degC. The HP Tuners log reported a speed of 239 km/h at ~ 1000 m. Not too bad with too bad launches. NOTE: I'm driving the black C5Z, which appear on the right. The attempt to heat the tires was not a success. Flyby at 1000 m. Think I have to do something about the exhaust, I had the most silent car off all.

Rear spoiler - SpoilerKing 284P

A small rear spoiler corrects the "missing link” on the rear end of the C5 FRC/Z06. After adding the spoiler there was a noticeable increase in wind noise, so it might also add some downforce.

Upgrade from 16 row to 30 row oil cooler

Engine oil temperature, the never ending story part #3 The 16 row oil cooler did help to lower the oil temperature, but not enough. I was advised that the absolute minimum was 25 rows, so I sourced a new 30 row oil cooler. I have to admit that I'm using a "Made in China" product, but the cost of a Setrab or Mocal was too high at this time. The G-PLUS brand does feature a stacked setup, but it might be that a Setrab or Mocal have a higher cooling capacity (BTU). I'll now when I get rich and buy a Setrab... 90 degree AN-fittings can cause flow restrictions, so I chose to bend the hoses when mounting the 16 row cooler. With the larger oil cooler, this was no longer possible as the bends would get too tight. To my luck, AN10 90 deg fittings still have a large cross section so the engine oil pressure didn't drop.

Trackday with throttle Auto-Blip

Trackday on Vålerbanen, 8 august 2021 My first trackday on sticky Hoosier tires. They provide magical grips levels, to an extent which requires pushing braking zones and cornering speeds far out of my comfort zone. Hope I'll be able to push harder next time. The throttle blip on braking is now managed by the Auto-Blip unit. It only took a few laps to calibrate it correctly, to get the delay and throttle blip to suit my driving style. The throttle-blip really helped to offload my brain on corner entry, where I've spent too much time coordinating all the steps. The engine is still running too hot when pushed above 5500 rpm, further cooling upgrades needed. Thanks to "Trackday Innlandet" for arranging the event.

4 wheel alignment for circuit racing

It was time for a wheel alignment after installing poly suspension bushings. I also wanted to a more aggressive geometry better suited to circuit racing. I asked for zero toe front and rear, which in my experience evens out the wear caused by the negative camber. I also like the handling with zero toe.

Auto-Blip, down-shift rev-matching

My CPU appears to have limited processing power, spending too much time to complete a successful rev-matched down-shift while braking at the same time. The end result is that I brake too much and too late, burning off too much speed. As my CPU is a one-off special edition that can't be easily upgraded, I decided to help it with a co-processor - the Auto-Blip Intelligent downshifter. After a quick test drive after installation, I conclude that two brains works better than one. I can now focus on driving the car, while the Auto-blip handles the rev-matching. The ever so difficult downshift to 2. gear is now a breeze. Designed to fit in that spot? The Auto-Blip kicks into action when you brake and clutch simultaneously, blipping the throttle at a configurable delay. The amount of throttle blip (how much the revs increase) is also configurable. I did have some issues getting the unit to work in my C5Z. The manual states to only connect two off the APP sensors (throttle position sensors

Hoosier A6 tires on square setup, 18x10.5"

I managed to source a set of C5 Z06 18x10.5" replica wheels with 315/35-R18 Hoosier A6 tires. It will be interesting to see how the A6s perform on circuit racing, as they are designed for short autocross sessions generating less heat. Sticky tires like these will not work with the stock suspension rubber bushings. Even if you adjust maximum negative camber, the rubber will deflect too much under load and screw up the alignment. End result is that the sticky tires can wear out in short time, especially the outer shoulder. To give the tires a chance to survive I'm installing poly bushings and changing to  more aggressive suspension geometry  settings.

Square setup with 4xC5Z OEM rear rims (18x10.5")

With the original staggered setup, the wheels can't be rotated to even out tire wear. This is a big minus as the front and rear tires wear quite differently. This can be solved by using the same rim and tire dimensions front and rear - a square setup. The wider front tires also improves the front end grip and shift the chassis balance rearward, which I prefer. The 14" Wilwood Aero 6 brake kit requires 18" inch wheels, and are known to fit behind the C5Z rear rims. I was fortunate to get two OEM rear Speedline C5Z rims from House of Wheels at a good price, in the same finish as on my car (there are variations in color).  They even survived the long distance travel from the USA to Norway without any dents. I have to issues with this configuration, no wheel arch or liner rubbing. This is how GM should have configured the C5Z.

Wilwood Aero 6, 14" big brake kit

The stock brakes hold up surprisingly well on track days, but rotors and brake pads burn off at an alarming rate. 2 track days on the rotors, 1-2 track days on the brake pads. I put a request on to purchase a second hand big brake kit. I got hold of an Wilwood Aero 6 kit, complete with spare parts and an additional set of new rotors.

Energy Suspension poly bushings install

Based on experience with tyre wear from the previous season, I knew that a set of Hoosier A6s wouldn't last long with the stock setup. With sticky tires, the rubber bushings deform too much, throwing off the alignment. Time for an upgrade. I was lucky to source a front and rear Energy Suspension poly bushing kit that someone had purchased, but not installed. Removing and reinstalling the upper and lower suspension arms was easy, although quite a bit of work on the rear, as the driveshafts have to be removed. The real challenge was to remove the rubber bushings. I tried with basic hand tools and a bench vise, but quickly gave up on the first bushing. Time to expand the toolset in the garage. A hydraulic bench press would be nice, but would take too much time - and money - to source. I found a nice toolkit for removing and installing bushing in the local hardware shop, which made the work surprisingly easy. With this toolset, you only need hand power to remove the bushings. The tools

Engineering Cooling Products (ECP) radiator

With a large oil cooler in front of the radiator, I noticed that the water temperature exceeded 115 °C. At such temperatures, the ECU starts to pull timing to reduce engine power output. I resealed the radiator shroud, cleaned out debris, installed a 160  thermostat (71 °C) and lowered the fan settings with HP tuners, but this was still an issue. The stock radiator had developed a hairline crack in the plastic end tank, which I discovered by luck when running the engine without the radiator and the fan shroud removed. A DeWitts or Ron Davis radiator was my preferred solution, but after adding shipment costs and import taxes the total was above $1000, so I decided to go for the less expensive Engineering Cooling Products (ECP) radiator for the C5. The ECP radiator arrived without any visible damage, which is always a risk when having fragile parts transported long distance. I bought it with a consumable electrode, to replace the flimsy petcock supplied.  The radiator installed nicely an

Flipped airbox to lower air intake air temperature

While stationary in the pit lane on a track day, I observed the intake air (IAT) temperature exceed 70°C. It took almost a full lap at speed to cool down the intake air again. High intake temperature sets of a series of events which reduces engine power and response. Increased risk of engine ignition knock / detonation The engine ECU retards ignition timing above 30°C IAT If the ECU detects ignition knock, the ignition timing will be further retarded by the ECU Time to do some improvements! By cutting the radiator shroud and inverting the airbox, colder air is drawn from the outside the engine bay. The most noticeable improvement afterwards is the IAT drops quickly after leaving the pit lane on track days, which was my main goal.