One of the unique characteristics of the Corvette is the leaf springs under the car. While they do function admirably, they’re expensive and time consuming to swap. Plus, removing them makes room under the car for the front splitter and diffusers.
Fortunately, the Penskes I bought for the car all those years ago have threaded bodies already, and have an old-style fine thread. A few calls to Penske and some used Hypercoils later, and now the car’s leafs are replaced with coils over the Penskes.
Got everything cleaned up, SCR Performance sent the shocks off to get tuned up and rebuilt, and back on the car they go.
Had a few wrinkles reinstalling. The holes in the rear of the chassis for the rear shocks were stripped out completely, so I had to drill them out and install AN6 bolts and jetnuts instead. Two of the bolts holding on the upper control arms were some oddball replacements, so I had to source some OEM bolts.
Installed ARP studs, LG Motorsports Spindle Ducts while everything was apart, so we’re getting closer to having the running gear ready to go…
After having done a bit of a shakedown of the ol’ vette in January, I built up the ole list of things to do, and boy…it got long quick! Going through the car has resulted in a list of a lot of thing sto fix, as well as improvements to make to take ‘er road racing.
Here’s the update:
Brakes – The car came with a set of Baer Eradispeed crossdrilled rotors, but those won’t stand up to time out on track. I sold those, and found a set of Stoptechs on CorvetteForum – 6-piston fronts and 4-piston rears.
Since the NASA TT rules are a lot more forgiving than SCCA SSM, I can get rid of the car’s interior. Here are the doors with the interior trim gone, windows removed, etc. Little bit of Sawzall work and here we go:
C5’s have a small cubby in the rear. GM left it in as a hedge against still having space for a spare tire, in case the new-at-the-time runflat technology didn’t pan out. For us, it just gets in the way. By cutting out that cubby, it not only makes access to the rear diff and gearbox easy, but gives us better room for a rear diffuser:
Had a fun test outing a few days back in the F1000, trying to shake off a bit of the rust from not having run much this season. Got some good new video with the new SmartyCam HD, and happened to run a new personal best, approximately two seconds under the track record, while scrubbing in some new tires. Enjoy!
Just over ten years after selling my 1997 Corvette to a good friend Mike Feldpusch, the ol’ car has come back to me, and once again finds itself in my garage.
With the continued decline in participation in the Colorado Region SCCA, coupled with the difficult logistics of racing far away with a one year old kiddo, I’ve found it hard to find events to run in the F1000 with any competitors.
So, I’ve brought the Corvette back into the fold to go Time-Trialing and Racing in NASA. With their focus on local racing, and the fact that so many of my friends from the autocross years have moved on to NASA and not SCCA, the draw is not only for better competition, but for better camaraderie.
The next few months will be getting the car prepared for track use after many years as an Autocross car. Should be a fun project re-learning how to work on the ‘vette!
Normally I don’t find myself writing this entry until after the Runoffs, but this year has definitely been pretty atypical, in a lot of ways. No Runoffs for me this year, unfortunately…
We only ran a few events this year, but did lots of test days during the preseason and during the season getting the Stohr dialed in with all of its new parts.
There’s a lot of fun stuff we did over last winter that I haven’t chatted about previously, so here goes:
Kawasaki Conversion – Over the winter, we converted the car from Suzuki power to the Kawasaki ZX-10R. With the 07-08 Suzukis getting older and increasingly more expensive, it seemed like a good time to make the switch to a newer engine. The engine has run without any hitch at all. The conversion was relatively straightforward, so here are some notes:
For oiling, we went with a BRD dry sump system, which connected to the same rear-mounted dry sump tank that we used with the Suzuki. As with all BRD parts, the fit and function are great, but you’ll wait a long time to get it.
The front sprocket is further towards the left of the car than it is in the Suzuki. To keep the rear sprocket aligned, we reversed the rear sprocket on its flange, and added 3/16 of spacers to move it towards the left of the car. This necessitated 3/16″ longer studs on the WRD diff as well. This has been problem-free.
The rotation on the shift lever is opposite than that of the Suzuki. I rerouted the shift cable for the car, and mounted the shift lever bracket on the front sprocket cover. The shift lever was a modified dirt bike lever, which we cut and reversed so that the mounting screw could be removed with the large dry sump scavenge pump installed on the engine.
Contrary to what I read elsewhere, the Suzuki headers did not interchange to fit the Kawi. Richard Cottrill at Rilltech made a nice header incorporating his oval muffler that tucks nicely behind the BRD bodywork
Just a note, not really a conversion specific thing: When starting, the Kawi seems to turn over really slowly – don’t worry! Your battery is fine, that’s just how it sounds.
BRD Bodywork – Since we’ve had the Stohr, drag has been a big problem. Zebulon did a CFD study of the Stohr stock body compared with the BRD bodywork, which showed that the BRD bodywork was on the order of about 40% less drag than the stock Stohr body, even after our removal of the drag-inducing rear body kickups. Fit and installation of the BRD body was excellent, and the parts are very strong, light, high-quality pieces – they look very nice. As typical with BRD, the wait was long, but the parts are very nice. Top-end speed has been substantially up this year as a result, the car cools well, and our wind tunnel testing earlier in the year correlated strongly with the CFD and verified the predictions.
Chassis Stiffening: In addition to the aero work we’ve done on the car with the Zebulon Wings and the BRD bodywork package, we did some analysis of the Stohr frame. It is no secret that the as-delivered Stohr chassis is not well designed as it relates to chassis stiffness. Triangulation is poor, in particular. To address this, Zebulon modeled the car using FEA, and by repositioning and adding only 6lbs of tube, we improved chassis stiffness by 65%, and we verified these measurements using the torsion testing rig that we built at the end of 2012.
Bonded Aluminum Floor Pan – Taking a page from most other formula cars, when replacing the floor, which was damaged beyond repair after the 2013 Runoffs, rather than continue with the original method of a single floor bolted to the bottom of the frame, we replaced the main floor with a bonded and riveted aluminum belly pan of .080 aluminum. Borrowing from the Citation guys, we extended the frame rails with 1″ steel strips to provide extra bonding surface for the floor. I can see why folks don’t do this very often – the amount of work was immense, and took over 700 Cherry and Solid rivets!
Spar Updates – At the end of the 2012 season, we replaced the aluminum spar with the BRD chromoly spar, which was a good improvement for chassis stiffness, but not as much as we hoped. We added more tubes to the chromoly spar over the winter, which addressed those shortcomings. Along with the chassis stiffening above, and the bonded aluminum floor, the car is now approximately 250% of its original stiffness, and the change in drivability is tremendous – communication from the rear of the car is much better, and the stiff chassis now enables the front anti-roll bar to be a very effective tuning tool.
So…how has it all worked out? Competitive results are hard to come by, as I did so little racing this year, but one good comparison is with Jose Gerardo and his car. Last year, we were essentially neck-and-neck on pace at most events. This year, I’ve been as much as 2.5 seconds per lap quicker in qualifying and testing sessions, so the changes have been hugely effective, and more importantly, the car is now likely very much in the hunt in terms of national competitiveness!
Now I just need to find a way to get the driver there…