in response to an often asked question
Re:68-72: there are some small bulges across the nose panel surface, along the cutout for the hood opening. I understand that there are production rivets in this location. Can the bulges be sanded down? Is it body filler (plastic solder) or fiberglass over the rivet heads? Will the bulging reoccur, due to corrosion of the rivet heads or shrinkage of the fiberglass? Should the old filler be dug out, or the rivets drilled out?
68-72 Header Bar, Bonding Strip and Rivets.
The pop up headlamps, their housing, support, actuators and mechanism are mounted to the underside of the top surround via a channeled Steel beam. On 1968 to 1972 models this steel beam has a similarly sized fiber glass bonding strip mounted to the upper surface with 2 rows of Aluminum rivets. The fiberglass bonding strip is in turn bonded to the underside of the top surround.
These Aluminum rivets mount all types of Steel brackets to the fiberglass and are exclusive to and specifically designed for and used throughout 1963-1982 Corvettes. Most rivet follow a rule of the head diameter being twice the shaft diameter. These Corvette exclusive Aluminum rivets have a shaft diameter of 1/ 8 inch (.125") but a head diameter of 1/ 2 inch (.500"). These big flat head are necessary to prevent the rivet from pulling through a soft substrate such as fiberglass. Normally the location of these rivets throughout the body does not become apparent when they corrode.
Galvanic corrosion between dissimilar metals (Steel & Aluminum) causes these rivets to "grow" and thus the heads enlarge in size and literally push up under the top surround. As you know this becomes very evident in the small bumps forming a V shaped pattern in 2 rows between the headlamp and the opening for the hood. During refinishing and repainting these bumps can be addressed in all four manners.
1) Drill them out and fill the holes. This is not a good idea at all. The fill in the holes will shrink and you will have sink marks where every bump was located. They have not yet invented a satisfactory Corvette filler that does not shrink. Any Corvette that had the holes filled from a luggage rack mount removed will show those holes eventually as sink marks in the deck lid.
2) Grind then down, then repaint and refinish. Eventually, they will again produce small bumps. This is the cheapest solution.
3) Remove the support beam, drill out the rivets and install new Aluminum rivets to mount the bonding strip and in less than 10 years you will again have small bumps. Or replace them with stainless ones to avoid the galvanic corrosion. Either is labor intensive and expensive.
4) Remove the support beam, drill out the rivets and install the bonding strip using a modern glue i.e. a superbonder. This is the manner in which the 1973 to 1982 Corvette mount these pieces. Again, this is labor intensive and expensive.
In all repairs, evaluate the cost versus the return. If it's a L-88 triple Black convertible with factory side pipes don't hesitate to do it the "factory way". If not and you are not Bill Gates make your judgement accordingly.