Corvette 99 Convertible
I found this Corvette from corvetteforum.com-marketplace amongst with a ’97 Coupe at spring 2009. I had major challenges to get these cars to Finland since the seller wasn’t up to his words after getting the payment. Finally after 4 months fighting over the phone and e-mails, both cars leaved New Jersey. I got them in November that year and after seeing the cars my plans changed a bit. I was hauling the red coupe in a trailer and the vert was in front of me. In sunny fall afternoon seeing the Nassau Blue convertible just re-organized my visions. This beauty deserved special attention.
The coupe had a manual transmission and the convertible was automatic. The convertible was damaged in front bumper/radiator area and needed both inner fender liners, bumper and was missing a hood. I have been studying about different supercharger setups and one of those met my expectations at least in paper: Magnacharger positive displacement supercharger. This wasn’t my first forced induction project and I had some experience with Eaton PD units. My goals were not being the top end power dyno queen. Instead of that I wanted a linear horsepower curve with instant reaction of touching the throttle at any rpm. At that time I wasn’t aware of the fact that advertised power increase in states is something else than the power increase in Finland. I was going to find out and do something about it.
I started with disassembling everything. Since I had 2 similar projects going on at the same time, I had no issues of how to spend my time while I wasn’t working my day job. I took the manual transmission from that ’97 Coupe (that tranny was changed again later in this project). I made new wiring harnesses according to service manual so that the car is like it would have been from the factory if it had been equipped with manual transmission. Unfortunately this transmission was missing #1 and #2 gear so I had to solve that first.
After some earlier experience with C5 Corvettes I knew there were numerous little things which could be causing problems after a while and now it was I good change to do some preventive maintenance. Usually it’s hard to disassemble everything as much as needed, especially when a service guy is doing that for a customer. This time I really got everything apart so it was easy and even pleasant to do this overhaul.
At this point (winter 2009-2010) the engine plan was to assemble the s/c on it and make some bolt-on tuning to it. I replaced cylinder heads with CNC-ported units and picked a cam that I later changed to a milder one (after learning how hard it is to tune idle and cruise areas with an intake manifold almost without any runners). I used a Magnavolt fuel pump voltage booster and Ford #42 injectors. All of these changed later in version II but more of that later.
After the engine assembly and all the wiring tasks it was time to assemble all missing or damaged body parts back together. Usually in C5 corvettes there are many small cracks or misalignments around the car even though the car would look alright from a distance. While I had all parts separate, it was quite easy to strengthen them from areas that I knew were prone to fail in use. I used glass ball blasting to all aluminum suspension parts after disassembly and I installed Kooks 1 7/8” headers together with 3” X pipe and Magnaflow catback. I designed an ‘anti-roll-bar` to keep rear end from rocking to either side on heavy acceleration. I used C6 Z06 shocks in all corners. Again most of these changed in forthcoming winters after some track time and experience.
Finally after few hundred hours of labor in summer 2010 the car was ready to be painted. I disassembled it again so that all parts can be sanded and painted also from ‘not-so-visible’-areas. It was nice to see how a can of pearl silver turns to “Nassau Blue” with only few drops of red, blue and black. This color looks blue but in fact it has only few drops of blue. That makes it alter its tone due to lighting conditions.
After painting process I got to install interior parts and small details around the car. I changed seats to more rigid ones and I used original electric memory seat rails to get the position memory and steering column telescope to work with them. Extra gauges I hid to center console in place of former ashtray.
Fall 2010 I hauled the car to R-Motorsport where it was tuned on road and dynamometer. I got decent power out of it but not much more than was advertised by s/c manufacturer. After the dyno run I got to drive it to registration office and then it was time for the next winter and some detailing with it.
I fabricated a water/methanol tank from aluminum which included a level indicator and baffles. I had earlier moved the battery to trunk and now its former place was given to that tank. Above the tank lays intercooler’s water tank. Methanol pump sits in front bumper cradle together with intercooler’s circulation pump.
I bought head up display and installed it with compatible wind screen. Together with my friend we used 90 hours to sand the whole painted surface and polish it to a “piano finish”. I bought new convertible top also to match the flawless paint finish.
I tossed the voltage booster and bought RSI fuel pump hanger for two pumps. I wired them with relays using thick wires. All fuel hoses were now PTFE since I was aiming to use RE85 as fuel in the future. I also changed injectors to Siemens #63 because those #42’s were a bit on the down side on previous dyno runs. The suspension got C6 Z51 stabilizer bars amongst with aluminum end links. Engine HP was already at decent level and the torque curve was quite flat as I hoped it to be but something in me wanted more grunt…
Summer 2011 with my Convertible Corvette was fantastic! I drove 7000 km mostly roof down. I got some track time and nice cruises around Finland.
A dyno video from year 2011: *Click*
A video from Kemora race track from that time: *Click*
Even though I was happy with it, I needed something to occupy my nights and weekends. So winter 2011-12 was full of work. I desired Grand Sport wheels and to fit them to my car I needed to fabricate wider fenders. Front bumper was replaced and some attention to detail was done. One major thing was to rebuild the engine with quality pieces, blueprinting and balancing. I made an oil cooler to engine oil and brakes got completely redesigned. That wasn't done in one winter, instead I spent almost the whole summer '12 in my garage. With these investments only I could have bought one more Corvette… But this was the only way to upgrade both looks and speed in a reliable way.
Engine machining was done by a professional. It was also balanced and cylinder machining was done with a ‘stress-plate’. I did the assembly after deburring the block passages and many rounds in an industrial washing process.
To start with, I bought wider rear fenders which were so bad quality that I couldn’t use them even as a mold. I bought standard fenders which were cut in pieces and formed again. My friend made molds out of those with which he laminated new wider fenders.
Brake stuff was upgraded earlier with a good fluid and better brake pads but now it was time to upgrade them to a different level. Front brakes got floating 355 mm discs together with Stoptech calipers. Rear brakes got C5 front calipers with C6 Z51 discs (to be changed later..). I used C5 Z06 ducts in rear. All calipers were powder coated after glass ball blasting. Front ducts were made with Quantum Motorsport hub pieces and C6 Z06 modified ducts. I used radiator cowl to feed the air to the ducts but I changed that also later.
Summer 2012 Corvette meet at Himos, Jämsä was the debute for the “Vert II”. I drove there but I hauled the car back with a trailer. The reason was one ignition ground contact bolt being 1 mm too long so the contact was lost and ignition was gone. However I got to test the car and its changes at last. It felt promising.
Fall 2012 just before Extreme Car Show in which the car was at display, it was time to wrap some metallic grey stripes to it. I designed the form and a skilled Corvette guy wrapped them by using a ‘cutting masking tape’ to make the form on the car. I spent almost all of my time tuning the engine in areas which do not come up in usual dyno runs. Day after a day it became better and more “factory like” to use.
I didn't get much seat time in fall 2012 since I broke the transmission output shaft quite soon after getting the car ready. The DTP-tuned transmission had something wrong with the output shaft and I got brand new parts as a replacement. I did get some idea of how some of my improvements work.
One of changes was the electric water pump which I replaced with traditional one during winter '12/'13. I also modified the brake cooling ducts. Innovate LC1 was replaced with more stable AEM wideband. I modified exhaust to accept catalytic converters and boost-actuated flaps in 2 exhaust pipes in rear. New transmission brace and stuff around it needed some modifying too. Of course I had to go through the driveline exercise again when I changed the output shaft and LSD-springs in rear end.
Last thing in the spring '13 was adding some noise insulation around the cabin and the boot.
Summer 2013 wasn't full of surprises. Vette worked like a charm. Remote controlled “show'n'go” license plate needed attention as well as exhaust pipe valves needed adjusting but other than that I was mostly behind the wheel instead of under the car. I changed rear brake discs to C6Z models because ball joint rubber boots melted with C6Z51 discs.. There’s a difference between Z51 and Z06 of how these discs draw air in and both of them seem a compromise. This was my second version and third is coming.. I got plenty of track time on 2 Finnish race tracks and 6000 km on the odometer. Nice!
A video from Alastaro race track from that time: *Click*
A video from Alastaro quarter mile: *Click*
A video from Lappeenranta airfield 1 mile: *Click*
2013-2014 winter included only minor updates: Catless X-pipe, polyurethane bushings with grease zerks, Comp Cams trunnion upgrade with shorter Magnum push rods, new s/c belt, smaller methanol jet and DRM shocks. Of course all fluid changes and small cleaning inside and under the car. I was hoping to improve last summer's lap times soon. The power did not decrease in these small updates…
Summer 2014 I didn't drive as much as I planned to. Not that Vette wasn't drivable, I just had other projects going on. I visited track a couple of times and was a bit disappointed on only 0,4 sec improve in lap time. I tried with stock rear calipers but I wasn't happy with them. It seems I've stepped over the line where I need to decide whether this is a track car or a street car.
If I would aim for major improvements in lap time, I’d have to keep another set of tires and brake pads with me. Now the setup is comfortable on the street and still capable of 1.27 lap times at Alastaro and 1:20.5 at Kemora. I think this is what I was looking for.
I checked all the hp again in R-Motorsport hub dyno and put catalytic converters back on (-20 hp decrease in hp due to couple of degrees less timing). Truthfully said it’s not needing more hp for track nor the street.. It would be nice to have more on a mile on airfield but this setup suits my needs perfectly as it is.
Winter 2014-2015 I made some service to brake calipers and designed a support structure to front lower A-arm bushings which were tend to “walk” at track use. I changed rear brake rotors to grooved type after I had bad luck with other types. New Z06 springs needed some height adjustment and I made stiffer adjusting heads to those bolts.
Season 2015 included one nice 'archipelago trail'-tour in the beginning and after that the weather didn't favor convertible driving, so the car was parked in the garage for quite a long time. In the end of the summer sun shined again and I got 4000 km altogether in the odometer. I participated for only one track day but I didn't improve my lap times. The car did though steady lap times within 0,5 sec many laps in a row. I had to repair my front license plate holder and I made a little more room for the rear hub bolts in the wheels.
Winter 2015-2016 I decided to do something for the exhaust which was causing drone in certain situations and while I was in there, I improved heat shielding and exhaust routing. Transmission brace and right side exhaust were fighting over the room there. Heat shielding was needed in the rear more than I was expecting.
I did a test of stiffening the trunk floor with aluminum profile glued/riveted to it from underside. I replaced cold white park led-strips with warm white. I also used relays to shut down fog lamps while the signal blinker was on so that in bright daylight it’s more visible. The fuel pressure sensor was changed 3 times already and now I changed the whole sensor type and brand to get rid of the quality issues.