text and photography by John Pfanstiehl
A problem or two is lurking underneath the gleaming fiberglass exterior of your Corvette. I'll bet on it. During my years as a mechanic at Corvette Center in Connecticut, I was under the hood and greasy underside of hundreds of Corvettes. I observed that 1963-1982 Corvettes have a lot in common, and this article concerns their common trouble spots. The following checklist was developed to be routinely performed on any Corvette which came into the shop.
Few of these inspections are found in the GM service manual and they certainly aren't done by the local "quick lube" franchises. The full inspection is worth doing at least once when evaluating or buying a Corvette, and with the exception of the one-time frame and number checks, most of the other items are worth checking during every oil change.
Grasp the outer edge of the fan and press it forward and backward to observe the clearance of the fan clutch and the water pump bearings. The fan clutch normally has a fair amount of clearance but wears slowly. The water pump clearance can be observed by watching the pulley's movement relative to the pump housing. Water pumps typically go from "loose" to "leaking" quickly, so keep an eye on them and listen for a dry howling noise to indicate bearings which are near the end of their life.
Check the clearance between the shroud and the fan blades at both their forward edge and their outer tips. Loose bolts or brackets, parts bent or misassembled after collision damage, and weak or broken motor mounts make this a common problem area.
Remove this bolt to add grease to your steering box, particularly if you aren't sure if it's been done before. Steering boxes are expensive to rebuild, but they can last hundreds of thousands of miles if lubed and adjusted properly.
The flexible coupling or "rag" joint is a reinforced rubber part which deteriorates under the heat and vapors of an engine compartment. Look for splitting or delamination of the rubber and for signs of wear or contact on the extended heads of the bolts.
Look for movement at the splines of the shafts while someone moves the steering wheel back and forth. Powdery red rust around the splines is a clue that they're loose, too. Use a 7/16-inch twelve sided socket to remove the bolt, then wire brush the threads and lube them before reinstalling and tightening.
It's no fun to lose your clutch in traffic. This is the type of spring clip that should be found holding the clutch rod to the bell crank. Cotter pins are softer than the spring steel clips and will wear until the rod pops off.
A small metal lock plate was used to help keep the bell crank's outer end fastened to the frame bracket. The plate has a flap which extends into a slot in the bracket and has two tabs which can be bent over the nut to prevent it from loosening and eventually falling off.
Look for deterioration of the rubber boot on the clutch rod. When new, the rubber is very soft and pliable, but it becomes brittle with age. A tear can allow a stream of hot engine compartment air to be directed at your feet while driving.
Check the hood hinge for excessive play and loose or missing bolts. The bolts are 5/16 to 5/18-inches, but make sure they aren't too long. Many Corvette hoods have been disfigured by installation of too-long hinge bolts. Also look for deteriorated or missing rubber weatherstripping used to seal around the radiator and radiator support.
The rubber bushings can show cracking and even peeling of some of the exposed rubber but still be functionally good if the outer portion of the bushing remains centered on the shaft. Check the tightness of the bushing bolts (9/16-inch wrench) and the nuts. Look at the alignment shims. If there is over 3/4-inch of shims, or none at all, there may be frame or suspension damage.
Clean and check the numbers stamped on the block. Learning whether the motor is original or not is a priority for almost all Corvette owners and future buyers.
Check the belts not only for the condition of the rubber on the underside, but for how high or low they ride in the pulley. Belts that ride too high in the pulley are more easily thrown off when the revs climb, and it's getting harder to find proper replacement belts for older generation Corvettes.
All rubber hoses should be checked, but those closest to the motor suffer the most. Check for splits and hardness. Also disconnect the forward end of the vacuum advance hose (or attach a longer hose) and suck on it to determine if the diaphragm is cracked and leaking. Open the metal window on the cap to see if the points plate moves.
Engine compartment wiring harness ground wires are always worth inspecting on a Corvette. On earlier models, one is located on the rear side of the radiator support. On later models, a ground is on the driver's side front of the support. Further forward, the headlight supports are also grounded.
Check the clearance between the radiator and its support and shrouds, and remember that the radiator expands and jiggles around somewhat. Whether aluminum or copper, radiators are fragile and their attachment points should be rubber isolated. If left to rub against steel components, they will be damaged. Also feel the underside of the radiator and heater hoses for any wetness. With some hose clamps, it's a fine line between undertightening and overtightening. Don't tighten clamps so that their edges cut into the rubber.
Check the clearance wherever fan belts come near hoses. If the belt is within an inch of a hose, feel underneath the hose to see if the belt has begun cutting into it. Remember that the belt dances all over the place when the motor is running. I've seen many Corvettes overheated and stranded on the road due to abraded hoses. If clearance is tight, install an additional clamp over the problem area for protection.
The rubber AC hoses run close to the exhaust manifold and are susceptible to premature aging. Check for cracks or leaks at the exhaust manifold and wrap them in heavy aluminum foil or tape if you want to help protect the hoses from the direct heat. With the cost of refrigerant today, it's worth the effort to prevent a hose failure.
Look at the outer steel ring of the harmonic balancer for signs that it is shifting. It is only held on by rubber and can eventually work its way loose. Tell-tale signs include paint rubbed off the timing cover or an apparent wobble of the ring when the motor is running.
Check the intake manifold bolts once a year or so to see if they have loosened. A 9/16-inch box wrench works for most, but the rear bolts can require a swivel socket.
Look at the routing of the heater hoses, particularly if they come close to the upper A frame. Originally, brackets kept the hoses away from the A frame, but all too often the bracket was not used or the hose was routed improperly so that it falls onto the A-frame. You wouldn't think the A frame could wear through the hose, but the constant movement up and down during driving can rub through it.
Grasp the top and bottom of the tire and push in and out to check the wheel bearing play. The tapered roller bearings and their clearance with the spindle create a very noticeable amount of play even when they're good and properly adjusted. If the play seems too much or if the wheel feels rough when it is spun, remove and inspect the bearings.
If the lower ball joints are still attached by rivets, either they are the original ball joints and are likely to be loose, or a restorer went out of his way to make the replacement look original. To check the ball joint for looseness, take the weight off of it by jacking up the A-frame close to the ball joint. Then pry up on the tire while looking closely at movement of the lower part of the spindle with respect to the A-frame.
Check the tightness of the bushing bolts on the lower A-frames. If they are very loose, tighten them only when the car is back on the ground so the A-frames are at their normal riding height. While the 5/8-inch box wrench is in your hand, check the two front bolts which attach the lower A-frame bushing shaft to the frame.
Look under the upper A-frame to check the condition of the cone shaped rubber snubber. Don't worry about minor cracks in the surface of the rubber. Replacements are inexpensive and fairly easy to install if the old one is torn or missing.
It is not uncommon for the exposed lip of rubber to become separated or curl off of a Corvette A-frame bushing. Although it looks bad, there is no immediate need to replace the bushing if the rubber is in good condition and keeping the inner and outer sides of the bushing apart.
The sway bar links seldom look good, except when first installed. The geometry of the Corvette suspension mashes the upper portion of the links and the result is that the upper rubbers generally look mauled. When they begin to get deep splits or are getting pushed out on one side, it's time for replacement. Save the bolt and nut for originality because the replacement nuts usually use a 1/2-inch wrench instead of a 9/16-inch wrench.
-John Pfanstiehl is a contributing editor to Corvette Fever and is author of the new Corvette Weekend Projects by HP Books.
Author's Note: Thanks to John Dubois of VanSteel Mint Restorations, 1141 Court St., Clearwater, FL 34616 for the use of his lift and his 1964 coupe for many of these photos.