Tuesday, February 1, 2011

C3 Corvette Driver Frame Off Restoration Part 2

The article featured on this page is from the February 2011 issue of Auto Enthusiast Magazine.


A hands-on approach to bringing back a C3 Corvette chassis.

Story Chris Petris

Images Stephanie Petris

We left off last month with a ’77 Corvette in multiple pieces that needed attention. The daunting task ahead is to prep, paint and assemble all the pieces that are back from the sand blaster.

We could have possibly saved a few bucks by wire brushing, sanding or scrubbing on all of the steel/iron pieces. The problem is, time IS money. Even those of us who believe the adage “I’ve got more time than money” can spend more money than they realize. We call them consumables in the business. Items like sanding discs, wire brushes and blasting sand for instance, have a limited life span. We would require plenty of consumables to get even close to the raw finish the sandblasting provided. Then consider this, squeezing air into a tank costs more than you typically think in electricity and compressor wear. If you have ever had the pleasure of sandblasting many pieces of iron during a hot summer day you realize the value of this service. Professional sandblasting companies use proven equipment that takes hours compared to days, if not weeks, that it would take us to do the same work. Certainly there are good sandblasters available for home or occasional shop use, the key word being occasional.

While the parts were away, we still had plenty of small pieces to prep for reassembly with our small bead blast cabinet. For the most part, there were no surprises when we inspected the sandblasted pieces, just some tape to remove and plenty of washing. To backtrack a bit, we used a good quality duct tape to cover any area that we didn’t want to be blasted. We wrap the machined surfaces of all chassis components a few times to keep the grit off of them. Another thing that we do is remove any oily sludge off of the pieces before blasting to prevent oil contamination on the raw metal pieces.

Momentum is Building

Once the parts are inspected, the cleaning begins with a thorough washing using a citrus-based cleaner to remove any blasting media. This is the most effective way to assure no blasting media is left behind to mix with any of our fresh lubricants. We have to work fast as the citrus-based cleaner and water rinse causes an immediate rust haze to form on our blasted pieces. We clean a piece and then apply Ospho or metal treatment to eliminate the haze and prevent further rust formation. We are careful to use Nitryl gloves for two reasons: skin protection and keep the oils in our skin from contaminating the prepped pieces. One of the worst possible scenarios is to let the blasted pieces get wet or leave them unprotected for a long period of time. All the hard work of blasting is for naught, more work will be required and the raw surfaces can be damaged extensively.

The chassis itself takes a while to prep, so plan on spending the day alone on the frame to make sure you can do all the cleaning and metal prep before you call it a day. We spent three long, hard days prepping all the pieces and the frame for painting. The prepped pieces were hung in our impromptu temporary spray booth to keep them dry and dust-free as possible. We applied our first coat of urethane primer to seal all of our steel/iron pieces. Zinc chromate primer was applied to the few aluminum pieces to assure that our topcoat would adhere well. The majority of pieces received a two-part urethane black top coat. Cast iron coat was applied to all the cast pieces to give some contrast.

When you are into a major project like this there are many choices to make, including which suspension bushings make sense. Rubber bushings work well for many years without any squeaking or groaning. Rubber deteriorates over time and allows flexing of the suspension components. Urethane bushings are durable, providing tight suspension control. Rubber bushings twist their rubber material for suspension component movement while urethane bushings act more like a bearing. The urethane bushing has freedom of movement throughout the entire range of suspension travel. The downside is, urethane bushings ride harsher and make some noise depending on the weather. We considered all the factors, deciding on urethane suspension bushings with rubber body mount cushions. This combination allows a tight suspension feel with smooth ride. We also had to consider the differential mount cushion material. Knowing that there would be no hard-core racing in the ’77’s future, rubber made more sense to mount the diff. Using urethane differential mount bushings would remind us every time we put the transmission in gear with a noticeable bump.

Instead of bolting the upper and lower ball joints in place, we used rivets from Zip Products to secure them. GM has used rivets in many areas of Corvette assembly over the years and this was one of the few rivet bucking tools we didn’t have. The rivet back-up tool we purchased holds the rivet in place while our air hammer peens the ball joint rivets.

Now that the pieces are arriving, we can move ahead with assembly after prepping all the threaded holes. Chasing all the threaded holes with thread taps eases assembly allowing proper tightening. After cleaning all the threaded holes in the frame and components they were washed carefully and oiled.

After three days at the assembly bench, we had the trailing arms, axle shafts and differential ready for installation. We installed all of our urethane bushings in the suspension components. This approach to sub-assembling components before installation makes it easier to assure correct assembly. Working at the workbench with pieces in your face so to speak lets us see each piece clearly and how well they fit. Once the sub-assemblies are completed the frame assembly goes quickly, making the project a little easier mentally. Planning is the key, however you approach the project.

We decided to start hanging the front suspension assembly on our chassis. We replaced the upper and lower control arm hardware with correct pieces from ZIP Products. Bolt and nut fatigue is inevitable after 33 years. Why chance the most important fasteners on the chassis? While we’re on the subject of fasteners, when corroded rusty bolts or nuts are cleaned with harsh cleaners or blasted, they will corrode very soon afterward. Original equipment bolts and nuts have various coatings to prevent corrosion. There are a few ways to preserve the factory finish. Brass brushes typically don’t remove the coatings. Mineral spirits and bristle brushes also are kind to the bolt coatings. The other approach is to apply a coating to the squeaky clean fasteners. When we have fasteners that are difficult or almost impossible to find, we apply paint to seal the surfaces. The paint is applied after installation and torquing is completed.

Our next task is to hang all of our sub-assemblies on the rear of the chassis. We used stainless steel fasteners for the trailing arms to avoid the same difficulties we had removing the original steel bolts. Another trick or tip is to apply grease to the bolt shank where it goes into a component. The grease keeps corrosion from forming and allows easier removal in the future. Once the suspension was installed, the new stainless steel fuel and brake lines were secured using new clips and fasteners. We decided to increase the original quarter-inch fuel return line to five-sixteenths just in case fuel injection is in any future plans; much easier to make the fuel line change now than wait until the body is in place on the chassis.

The ’77’s owner mentioned that his Foose wheels were wide open and he really didn’t want the factory iron calipers showing through them. The caliper change was understandable. Wilwood was the owner’s choice and how could we disagree? Wilwood calipers not only look great, they would enhance the brake system. Their 6.3-pound aluminum calipers front and rear keep a few pounds off the spindles. Wilwood kept the caliper piston diameters at the GM spec to assure pedal feel and travel would feel the same and, the stainless steel caliper pistons will keep them trouble-free for years to come.

While we waited for the calipers and disc pads to arrive, we set the engine in place, coupled to a fresh 700R4 O/D transmission. Routing large diameter exhaust pipes through the crossmember exhaust opening, then past the 700R4’s pan is quite difficult.

Edelbrock carburetors have never been factory installed with a 700R4 transmission. We would have to do the trial and error method. This can be death to a good transmission and any TV issues can cause poor shifting and clutch failure.

The body will be ready for installation after some items are attended to on the firewall and underside of the body. One other thing we certainly did not want to forget was to install the positive battery cable in the trans tunnel. We’re installing an upgraded Taylor battery cable kit that requires custom fitting. The custom cable fitting may require us to remove and install the cable a few times to get the correct length. Battery cable removal is much easier with the body separated from the chassis. Before we drop the body the A/C firewall pieces will be restored. The owner removed the A/C evaporator and plenum leaving us a clean firewall ready for installation of restored pieces. After we restore the A/C pieces they will be installed and the body is ready for installation.

Sweat Equity

The owner certainly put plenty of hard work into the engine compartment and underside of the body. This saved the owner dollars out of their wallet, but as we said earlier, you have to consider the time and effort you put into the project. The entire engine compartment was cleaned, primed and painted the eventual exterior color. Under the car, the same hard work was performed by the owner cleaning and prepping for urethane truck bed liner spraying. Using the bed liner as sealer and protection makes sense. Before the bed liner could be applied, the owner reinforced the floor with a coat of fiberglass mat and resin. There were no major corrosion perforations, just some small holes here and there. Applying fiberglass to the area made the structure solid and ready for the bed liner, which was applied inside and underside to completely seal the floor pan. Rocks and stones typically won’t harm the bed liner, keeping the floor pan in great shape for years to come.

The body will be installed in the following weeks and the wrap-up of all the necessary connections will be completed. Still plenty of things to think about and keep on track, making sure we have all the final pieces we need. Our planning has paid off and we’ve been careful to keep the owner aware of costs and expectations.

So far we have held to our numbers well and expect to come out close to our budget. The extra dollars spent on pieces were all upgrades, while labor costs have been close to what we planned. We did have an issue with our sandblaster with some extra charges. As we explained earlier, it’s a tough job. When you realize one of us would have to clean the pieces it makes the up-charge easier to swallow. The ’77 will be new in the respect of the drivetrain and upgraded at less than half the cost of a new base Corvette.



1 Our air powered die grinder does the hard work cleaning the U-joint cup bores. This takes practice. We remove just the paint and corrosion to avoid loose U-joint cups.

2 Urethane bushings make assembly so much easier. We are sliding the bushing out of the housing. The bushing sleeve that rides on the control arm is pushed out first using a socket to ease it out. Make sure the socket is a smaller diameter than the bushing or it will become wedged in the bushing.

3 We use a shop-built support that fits tightly between the control arm bushing mount areas to allow press installation of the bushing housing. The support fits closely to the control arm shaft as the housing is pressed into place. Do not forget to install the shaft before installing the bushing housings.

4 Like we said earlier, we easily push the bushing in after lubing it with Energy Suspension supplied grease. The bushing sleeve is next after a liberal coating of the specialty lubricant.

5 The anvil that the rivet presses against bolts to one of the lower control arm bumper mounting holes. Our air powered hammer with a rivet press chisel easily peens the rivet into place. No chance of bolts coming loose.

6 We always replace the control arm bushing retaining hardware with Grade 8 fasteners, which GM used. Then we apply Loc-Tite and torque to factory specs to avoid a major incident. If the control arm bolt backs off and comes out, the control arm can come off the control arm shaft.

7 One of our upper control arm to chassis bolts was bent and the others would spin in the chassis. This means the alignment guy would be very aggravated at alignment time. You can just barely get on to the bolt head to hold it if a shim change is required. We spot welded our new Grade 8 hardware in place to stop the spinning.

8 We are ready to start assembling the rear suspension and driveline components. The first step is to clean all the threads to allow proper bolt torque. Thread cutting lube should be applied to prevent galling the threads as you clean them.

9 Even our shock bolts receive attention from the torque wrench. Make sure the shock bolts are installed from the outside of the chassis. If the bolts are installed from the inside, the body will not allow bolt removal once it is in place. The torque wrench is on the nut of the fastener in this photo.

10 The trailing arm bushings require shims to give them a slight tension. Be careful! You have one chance to get the shimming correct. The washer is locked in place with the tool provided in the kit.

11 This is why you might want to consider having a professional do the trailing arm bushing set-up. The tool pictured allows us to check for proper bearing clearances without pressing the bearing in and out repeatedly.

12 Our bearing packer, with fresh synthetic chassis grease, forces the grease into the rollers. This is what you want to see, the grease coming out between the rollers not smeared on the outside of the rollers.

13 Light oil is applied to the bolt threads to prevent corrosion and assure proper tightening. Longer bolts with shanks passing through chassis components are coated with grease to prevent corrosion.

14 Once the bolts are installed, the bolt head is cleaned and a coat of the appropriate color paint is applied. The paint prevents corrosion forming on the bolt and eventually causing rust streaks.

15 We use a piece of exhaust pipe that fits the cap and catches the edges for the installation. Or, we could hammer on the new dust caps, denting them all over.

16 These are the pieces required for a true restoration of the steering box. Replacing all the wear items assures a tight feel without rough spots. All of our steering boxes are refilled with 75-90 synthetic lube for smooth, long-lasting steering control.

17 Now that’s a good looking set of calipers! The Wilwood front and rear caliper kits are direct bolt-on with all the necessary attaching hardware. Goodbye heavy iron calipers!

18 This temporary shelter is a lifesaver. The pieces can be painted and then left to dry for as long as necessary. Our shop floor is clear of the pieces, allowing us more working room without worrying about paint damage until we need a specific piece.

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