by John Pfanstiehl
There are only 8 body mounts on 1963-1982 Corvettes so replacing them doesn’t sound daunting. If a Corvette has led a truly dry, garaged life, body mount replacement is straightforward. However, most Corvettes 40 plus years old have accumulated a bit of corrosion on their steel components. Particularly affected are the parts and fasteners that often suffer rain and road splash.
That’s where this series of three tech articles comes in. Rusted fasteners can cause problems with this project. The assembly manuals and the service manuals can’t help here. This, the first article, will start with the body mount that is least likely to present a problem, the front, which is labeled #1. Then we will focus on removing the body mount that is most likely to present a problem, the rear mount, labeled #4.
The next tech article, 1963-1982 Corvette Body Mount Replacement Part 2, covers the particular problems and solutions for removing the bolts from the two central mounts, #3 and #4. The final article, 1963-1982 Corvette Body Mount Replacement Part 3, details installing the body mounts without removing the body after the 8 bolts have been removed.
The work shown here is on a 1973 Corvette, the first year that had rubber body mounts. The same rubber mounts were used until the end of the C3 run in 1982. The previous years, 1963-1972 used metal body mounts but the procedure is similar. Zip Corvette offers both of these types of body mounts in complete kits and also offers polyurethane replacements.
01: Zip Corvette offers a 1973-1982 Body Mount Kit that contains the mounts, bolts, nuts, washers and 16 shims. The 1973-1982 kit has rubber mounts and is USA-made. Zip also carries the 1973-1982 Body Mount Kit with Polyurethane Bushings if you choose to go that route.
02: The front (#1) mount bolts are the easiest to remove. Access to the right side mount is fairly open. Reach up to place a 5/8-inch box wrench securely on the bolt head.
03: Use an 11/16 deep socket on the nut. A ½-inch breaker bar or torque wrench may be needed to break the nut loose. After that, an impact wrench helps spin the nut off. Tap the bolt up and out. Note the #1 body mount bolt uses a thick washer.
04: On the left side, reach up over the frame or down from the engine compartment to place the 5/8 inch box wrench on the bolt head. On this car, removal of the splash pan was not needed.
05: The rear (#4) body mounts are often an entirely different situation. The bolt goes up into a small cavity which has a nut in a thin cage. Over years, water gets down into the cavity that surrounds the nut and its thin cage. When this happens, rust can eat away at the nut, bolt and cage. Zip Corvette offers replacements for all these parts.
06: The cage and nut are not visible. Pull the carpets back a little if necessary to access the cavity located in the rear compartment corners. Tip: Insert a magnet down into the cavity to determine if substantial rusting has occurred. If little or no rust is picked up, spray penetrant down there to increase the chance of unscrewing the bolt.
07: If a lot of rust particles and small metal pieces cling to the magnet, there is no sense in applying penetrant — unscrewing badly rusted bolts would be a lost cause. Plus it’s good to avoid the lingering smell of penetrant in the passenger compartment.
08: Alternatively, a scope can be borrowed from some major auto parts stores. A scope helps because there is no way to directly see the condition of the bolt, nut and cage. The deck lid spring and assembly need to be removed to replace the cage and nut. That is a subject for another tech article.
09: The scope image is fuzzy like an underwater video but it shows that the cage is gone and that this nut and bolt are seriously rusted.
10: Zip Corvette offers both a replacement 1963-1982 #4 Body Mount Nut Cage and a replacement 1963-1982 Body Mount Square Nut. Zip Corvette also offers the 1968-1974E Body Mount Bracket (shown on the left) for the middle two mounts (#2 & #3). The #4 cage is much thinner and often weakened or destroyed by rusting. It is riveted to body support while the thicker Body Mount Bracket nut-cage assembly is welded to the frame.
11: To remove a rust damaged rear bolt, first cut and peel away the lower rubber cushion. Note that deteriorated and cracked rubber mounts can hold water and catalyze corrosion in that area.
12: Then use a hammer and chisel to knock off any layers of rust to make room for a saws-all or a cutoff wheel.
13: Saw through the bolt with a saws-all using a fine-tooth metal cutting blade. Tip: shorten the blade by breaking off a few inches from its end.
14: After removing the bolt head, tap the bolt upward completely through and out of the old rubber mount.
15: A magnet can then be used to pull the remains of the bolt from the cavity. Vacuum any remaining rust particles from the cavity.
16: The extremely rusted condition of the two original rear bolts and nuts shows that there was no way to remove them except by cutting the head off.
The new rubber body mount shows how deteriorated the old mounts are after almost 50 years on the car.
1963-1982 Corvette Body Mount Replacement Part 1
Source: Zip Corvette Parts
8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632
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