In this article, Wayne Ellwood shares with us info on building a C4 Project Car. Wayne shares the history of the C4 Corvette Suspension quirks that were quickly discovered when the C4 Corvette took to the track in 1984. By 1988, with the evolution of the Corvette Challenge cars, GM had introduced the selective ride option to help soften the suspension to suit different driving conditions . . . a cheap fix.
WANT TO BUILD A C4 PROJECT CAR?
By: Wayne Ellwood
(Photos at the end of the article)
Back in 2012, I had the bright idea that there is a cycle to car auctions. Here, in the Toronto area, there is a collector car auction every spring and fall. The fall seems to be when the junk is offered. Then, in the spring (after a winter’s work) the winter’s project cars are put up for sale. Whether you attend the spring or fall events, depends on where you are in the cycle. For my part, I had no intention (or skills) to start such a project, but it occurred to me that when the donor car is cheap enough, a person could afford to play around with more complex ideas. (For original story, see VETTE VUES MAGAZINE, Vol # 450, Issue # 7, February 2012). This brought me back to the many Greenwood stories I had collected . . . Greenwood is the master of the project car.
But, first, some history on the C4 chassis/suspension issues that you’d want to hear before you look for some easy fixes for your C4 suspension.
John Powell (Corvette Challenge Series) may have been amongst the first to identify the fact that the new frame had a very poor bending stiffness (forward of the firewall) . . . somewhere around 4 Hz, when it should have been around 30 Hz. As a result, the shock absorber would actually bend the chassis as the spring and shock were compressing. This problem with bending stiffness posed quite a problem for maintaining control of the suspension.
For the most part, teams who figured out that something wasn’t quite right started by tweaking some of the basic settings. In this case, teams went in the opposite direction to normal race practices. Rather than being able to stiffen the chassis, they had to run the cars softer than stock and run them at street ride height. After that, the winner of any one race was often the team that found the best compromise in their suspension set-up, for any specific track on any specific day. One of the “street” improvements that resulted from this work was the new selective ride package.
When Greenwood started working on the “G” series cars (G350, G500, and the G383), he quickly discovered the same problem…and several others. John found the C4’s shortcomings were deeply rooted in some very early design trade-offs. From the factory, the C4s were built with a “bind” in the chassis to keep everything tight as possible. These on-line fixes weren’t too evident in the street cars but did show up in more powerful race cars. As a result, the solutions lay in a chassis correction. Without solving the original trade-offs, no amount of changes in the suspension would ever keep the car in total alignment.
The photos provided here illustrate the point. The front engine and suspension cradle provided increased torsional stiffness and bending moment. The roll hoops and cross –bracing in the trunk area perform much like a regular cage for racing. Not visible in this photo is the ladder-style bracing running the interior side of the frame rails. And finally, a cross-brace and driveline hoop under the passenger compartment could provide both strength and safety. Each of these assemblies was designed to be installed separately or as a total package.
NOTE: These photos do not show any of the final configurations as applied to the G-Series.
The last of the Greenwood C4 G-Series cars went out the door around 1994-95. The cars had not been a financial success, and business suffered.
A few years later, John also conceived the idea of bringing full chassis-suspension packages to market for the primary muscle cars. Owners would, theoretically, be able to upgrade their platform to supercar performance levels. As it turned out, John never got the chance to bring these ideas to market. But some other companies were moving in that direction. One example of this already on the market is from JME Enterprises, who specialize in Mustangs. In 2008 they brought out their new front cradle at the SEMA show. This cradle provides frame stiffening, engine mounts, and an upgraded (race-oriented) suspension system.
On the negative side, no such product as yet for Corvettes. What we’re left with is a wonderful concept waiting for its realization.
However, if you’re considering a C4 project car, you’ve probably got enough information to know where to start your own research…if you dare.
If you are ready to start your project, here is a list of contacts where you can get those Corvette Parts that you will need.
You might also enjoy reading about the history of Corvette design.
Check out a commercial spot that was produced by Chevrolet to promote the all-new fourth generation Corvette for 1984. The advertisement highlights many of the advanced technological features that made their debut on the Corvette. 1984 Corvette Commercial