In The Beginning
In the first installment, we addressed the research and planning for our project, including the up-front decisions, the car search, the project and building plans, initial budgeting, and our objectives and theme. In this installment, we will cover the chassis choice and the suspension.
Our main theme is to combine the first year for the Z06-model Corvette with late-model Z06 components, especially the LS7 engine. Our main objectives are to improve the handling, ride, braking, comfort, and performance, while retaining the original classic design. The car will be built with an emphasis as a show car, but it will also be driven, and that has driven our choice not only of components, but also the level of detail and finishes used. When you see the level of detail that we have taken things, you may feel you wouldn't plan to go to the lengths we have. You may even think we are a little crazy . . . but that's just an unconfirmed rumor. However, what we are building is in line with our objectives and vision for the car. The level to which a car is taken will have a huge influence on the project timeline and the cost. There is an almost endless variety of choices to make on this aspect that needs to be factored into your planning. While most folks may never plan to go to this extent, nevertheless, you should find the comments on choices, the details of the components used, and the assembly process of interest should you be contemplating building a car of this type.
Chassis: Choices, Options, And Finishing
Choices: The choice of frame and suspension is driven by several factors. Things to consider are the condition of your current frame, the extent of ride and handling improvement you are looking for, how you plan to use the car (street versus track), and how much effort, time, and investment you want to make. The good news is there are many choices available today; the bad news is it can make the decision a little more difficult. The Resource Guide in our February 2007 issue lists about a dozen sources. The choices range from changing the suspension components on your existing frame to using a new frame and suspension, such as that from the C5 and C4 Corvette. here are some things to consider when making this decision.
Condition of your current frame: We often forget that these frames can be 40-plus years old. If you've been around C2 Corvettes for a while, you are familiar with what to look for (such as the rear kick-up area) in determining its condition. To get the full benefit from a suspension change, the stiffer the frame the better. If the frame is showing its signs of age, a new frame may be a good choice, whether it is a reproduction stock-style frame or one designed to accept later-model suspension components.
Chassis design: With the C2, the frame design was changed to provide for the then-new independent rear suspension, and it was also widened to allow the passengers to sit lower in the car. To achieve this, the side framerails were placed further outboard and the X-member used on the C1 frames was eliminated. While we don't have any torsional rigidity numbers, it would stand to reason that some was likely lost. New reproduction frames will at least have the advantage of new metal, and the custom frames should be more rigid by design.
Cost factors: The least expensive route is in changing to an aftermarket suspension on your current frame. It's also the least involved in terms of work required. Some (such as that from Vette Brakes) provide for spring rate and ride-height adjustment. If you want to go further (such as using C4 or C5 components), the costs will go up as it involves either having your frame converted to accept these components or the purchase of a new frame designed for that purpose. There are also usually some modifications to the body, and those vary depending on your choice of frame. There are some cost offsets in buying a new frame. The major one is in selling your rolling chassis. Depending on its condition, it could help to offset quite a bit of your costs. Another factor is the shipping costs. Converting your existing frame involves shipping it twice, while buying a new frame entails shipping in only one direction. Depending on how far you are from the conversion shop can be significant.
Our choice was based on our objectives and having seen most of the custom frames in person at various shows, such as Corvettes at Carlisle. For us, a major factor was we like to do something different with each car. Our '67 used the Vette Brakes "Performance Plus" system on the original frame, and the '62 used a Car Creations conversion to the C4 suspension using the original frame. For this car we looked at chassis design for strength, build quality, use of late-model Corvette components, body modifications needed, cost, and how it looked. For us, the round-tube frame had all the right elements (maybe it's also the racing heritage of that design that appeals to us), and that led us to SRIII Motorsports (www.sriiimotorsports.com). Mike Stockdale has done a great job in his design, and the build quality is top notch. His frame uses the stock body-mount locations, the stock bumper-bracket mounts, and the stock fuel-tank cross-member. He also uses QA-1 coilover adjustable shocks that we wanted to try. His customer support has also been outstanding. While we don't yet have on-road experience since the car isn't completed at this point, the feedback from those who have used his frame has been positive.
Options ::: Once having made the choice to go with a new frame, the next decisions you will have to make include your choice of engine, transmission and differential, side exhaust or under-car system, the suspension to be used, and wheel width. Several chassis builders offer the choice of using the C4 suspension for both the front and rear, the complete C5 suspension, or a combination of the C5 in front and C4 in the rear. Most chassis builders have several levels you can select, ranging from just the bare frame to a full roller, or, in some cases, a turnkey car. Our choice was to have SRIII build the frame and test fit the suspension, which we supplied. You may find good sources for the suspension components and may save some of your cost by supplying it yourself. Having a roller may also help in shipping the frame. Three other options worth considering are the brake lines, type of weld used, and priming. We chose to have Mike run the brake lines since he knows the best route to take, and that saved us some time. We also chose to have Mike TIG weld the frame because of its better penetration and strength. He can also epoxy prime the frame, which is a good idea to keep things from rusting while you are building the car.
Finishing ::: While not necessary under normal circumstances, we chose to go into great detail on the frame because this car will be displayed with lights and mirrors to show the underside of the car at indoor shows. Each weld and seam was ground, contoured, and filled. Our midrise lift helped to get the frame to a reasonably comfortable working height and saved some backaches. We counted 427 welds and joints. After ten weeks of this work we were beginning to wonder if we would ever get to the last weld.
When considering whether to go with paint or powdercoat, we highly recommend powdercoating. Because of our custom color we couldn't find a powdercoat close to the color we needed, and while you can order a custom mix, the minimum quantity and cost was outrageous. we had no choice but to paint the frame with our mix using RM Diamont base and clear. Corvette Center in Newington, Connecticut, applied the final coat of epoxy primer and the base and clearcoats. It was then polished and waxed before the suspension was assembled.
We ended up strapping the frame to our lift as it was so slippery we were afraid it would slide off.
If you do decide to go the paint route, here are a couple of things that can help. First, buy or borrow a chassis rotisserie. It will allow the frame to be rotated so you can get at all surfaces. One source is Accessible Systems (www.accessiblesystems.com). Second, if you are using a base/clear paint, two painters in the booth at the same time can help, especially when it comes to applying the clearcoat. With the round tube it is almost impossible to avoid either missing an area or over-spraying. With the second painter you can keep the clearcoat "wet" and get a more even coverage.
Suspension: Choices, Detailing, And Finishing
Choices ::: C5 or C4 or a combination: Since we had used the C4 suspension in another car, we wanted to use the C5 suspension in front, which also provides a little more room in the engine compartment. In the rear, we considered using the C5 rear-mounted transmission/differential, however, the changes necessary to the fuel tank and rear body areas led us to go with the C4 suspension and a Dana 44 differential. We wanted to retain the stock body width, but still use the 911/42-inch-wide wheels, which required narrowing the differential carrier, rear toe-rods, camber rods, and a custom sway bar. It also required moving the rear inner fenderwells in about an inch and a half on each side. You can, however, use an 811/42-inch-wide wheel and avoid having to narrow those components. On a coupe, narrowing that area isn't a problem space-wise, however, on a convertible, narrowing the space between the wheelwells can restrict fully lowering your convertible top. Another option, which avoids having to narrow the components, is to widen the rear quarter-panels. There are sources for these quarters which will provide the space needed to accommodate a wider wheel.
Springs and shocks: There are two approaches taken by the various chassis builders. One uses the monoleaf fiberglass springs, while the other uses coilovers. One thing to keep in mind when making a spring choice is the car you are building will typically be lighter than the car the stock springs came from. Usually you will find that a lower spring rate will provide a better ride. There are sources, such as Vette Brakes, that make the monoleaf springs in different spring rates to suit your combination of components. For this project, we wanted to use the coilover spring and shock and chose the QA1 units. The front spring rate is 350 pounds, and the rear is 250 pounds. The shocks are adjustable with twelve different settings. we are starting at setting "3" as a base setting.
Detailing ::: We wanted to carry the detail for each suspension piece further than we've ever done before. First, each piece was disassembled and bead-blasted to clean it. Then began the regimen of grinding, filing, and sanding each piece to remove all the seams and part numbers and recontour to the shape we wanted. This is a good example of where the level of detail can really extend the amount of time you spend on your project; this aspect alone involved over 950 hours of our time. While some tools (such as the Multi-Mate stationary belt sander, Dyna-File II hand-held belt sander, and Dremel Tool) helped to rough out the shape we wanted, approximately 75-percent of the time involved work by hand using various files, sanding blocks, and dowels wrapped with various grits of sandpaper. Once the component was taken to a 1,500-grit level, it was then polished. This isn't something we would recommend doing and likely will never do again.
Finishing ::: After the experience (and pain) of going the route we did, good old powdercoat now appeals to us more than ever! But since we went the polishing route, we needed to look ahead to future maintenance since the car will be driven. If you do decide to go the polishing route, it's a good idea to apply some type of protective coating to reduce or eliminate having to get back in there to keep things looking good. We searched for a clearcoat that would provide protection while not reducing the polished shine. We did tests using clear powdercoat, but that reduced the shine more than we wanted. Next, we tried a POR-15 product called Glisten, which is a two-part mix, and that worked better from the shine standpoint once we found the right level of thinning and how to apply it. We used that on the transmission because it appears that it can stand higher temperatures along with being durable-a good option for that unit. However, after all that work in polishing, it still wasn't quite what we wanted as it does take some of the luster away. So we tried a new product called Chrome FX, which is advertised as a spray-on type of chrome finish. A friend, who is in the coatings business, tried it, and the early results looked promising. However, we couldn't get the final third stage to work the way we wanted. Further experimenting might have produced better results, but we were running out of time.
After all that experimenting, we decided to take the regular chrome route for appearance and durability. Actually, I guess there is no such thing as "regular chroming" when it comes to aluminum, especially for the cast-aluminum pieces. One key aspect of chroming is that its quality depends on the density of the part and its shape, which impacts the electrical flow. Forged-aluminum parts chrome well, but that's not always the case with cast aluminum. We ran into a major issue on the cast pieces where the porosity caused a problem in getting the copper to stick well and flow evenly. It looked like we were at a dead-end until we discussed the problem with Har-Conn Chrome (www.har-conn.com). They have almost fifty years of experience in coatings for the aerospace industry and had a process to seal the aluminum and get the copper to stick. They now have a new subsidiary called Anvil Power Stryke that does powdercoating.
Once that problem was solved, the parts were taken back to Allied Metal Finishing in South Windsor, Connecticut, to complete the chroming. These folks also have decades of experience in chroming for commercial and decorative chrome and, fortunately for us, make the sacrificial lead anodes used to get the chrome to flow into recessed areas. Some of these are extremely complex and almost look like works of art.
For those parts which cannot be subjected to chemicals or high heat, such as with chroming or powdercoating, they can be polished and protected with Zoops Seal. We used that for parts, such as the tie-rod ends and stabilizer links.
If you plan on driving your car regularly, our suggestion would be either to leave the suspension "natural" or use powdercoating.
Front Suspension: We started by installing the lower control arm, followed by the coilover, and then the upper control arm. The hub knuckle, with the bearing hub already mounted, was then installed, and the ball joints were torqued to specs. Lastly, the sway-bar brackets, sway bar, and stabilizer links complete the suspension itself. Then you can install the rack-and-pinion and connect the tie-rods. It's a good idea to leave everything loose at this point until you are sure everything is as you want it, and then torque all fasteners to spec.
Rear Suspension: A second pair of hands can help with the rear suspension, especially when it comes to installing the differential and when connecting the components to the rear hub. We started by installing the differential carrier assembly. This assembly includes the carrier and differential, torque arm, and camber-rod brackets. Then the trailing arms were installed to the chassis. The next step was to have someone hold the hub assembly (which consists of the hub, brake mount, and bearing) while the trailing arms, coil-over mount, and camber rod were assembled to the hub. Then the rear toe-rods can be installed. Lastly, the sway bar brackets, sway bar, and stabilizer links are installed, which completes the rear suspension.
Bushings: If you disassemble the suspension and remove the stock bushings you will have to replace them. There are two schools of thought when it comes to using rubber versus polyurethane bushings. Some folks like it, while others don't. On some components (such as the C5 upper control arms) the only ones we found were polyurethane. They do look good and will likely last forever. one caution: use enough of their special lubricant to avoid squeaks. The lubricant is nasty stuff to work with and hard to get off the parts and your hands. One product which helps is the 3M General Purpose Adhesive Cleaner (PN 08984), which is handy for other uses around the shop as well.
Hardware: For mounting hardware, we used high-strength six- and twelve-point stainless bolts, washers, and nylock nuts-each of which were polished. One word of caution: when working with stainless, use anti-seize as they can "cold weld" themselves together if you don't.
Well, that's where we are at this point. It sure was nice to finally get into the assembly stage and see things come together after spending all those hours preparing everything. At times during a project you wonder if you are having fun or not. there are a few of those times along the way during any project, but having things come together as you had planned makes it all worthwhile.
In the next installment, we'll cover the drivetrain, including the engine (accessories, mounts, electronics, and dry-sump system), the transmission and clutch, the differential, and the brake system. In the meantime, you can find additional pictures and links to sources on our web site: www.corvetteforum.net/c5/richs7/.