Here are the improperly tapped holes. The vacuum relays mount here and you can see that I wasn't even able to get to one of the locations. These were made with a 10-24 tap. In this picture you can also see a reinforcement plate and how extensive the corrosion was.
Click through the slides and review the repair sequence. It starts with three 2" long 10-24 machines screws smeared with JB Weld at the ends. I ran them into the tapped holes until the threaded end was flush with the original surface. After they cured, I used a dremel cutting wheel and grinding stone to remove the excess material. I drilled new holes with my drill press and tapped them. While not perfect, they are much better than what was there.
Next I removed as much rust as possible with a 3" wire wheel. To remove the rust from underneath the reinforcement plates, I hit the plate in several areas with a hammer and blew the powdered rust out.
Zero-rust is a Direct to Metal paint that goes on top of corroded metal as long as scale and heavy rust is removed. However, I was concerned about the bonding surface between the header bar and hood surround. As I mentioned in the walk through, I was able to remove the header bar by hand. I wanted the adhesive to have a good bite into the metal, not lay on top of rust.
Unfortunately, the bonding surface was pitted, so even after I removed a lot of rust with a 2" sanding drum, there was still some left behind. As a remedy, I sprayed Permatex Rust converter on the adhesive surfaces and removed it with a sanding drum. The pits that remained contained converted rust, as seen at right.
Then I sanded the adhesive surfaces with a 36 grit wheel to give the adhesive a good biting surface, and masked them off.
Next I reduced some Zero-rust until it was very runny and soaked a foam paint brush in it. I dabbed the paint brush along the edge of the reinforcement plate until Zero-rust started running out from under the plate. I don't know how well this will work, but it was the only way I could think off to treat the rust on this piece.
Here's the header bar drying after the last coat of paint. You can see brush marks, but virtually no one sees this piece of hardware and I was interested in making sure it was well protected. You can easily see the pitting, so it was far from a smooth piece of hardware anyway. I will leave the tape on the adhesive surfaces until I glue the bar in place.
SUMMARY: This job was a 3 out of 10. The hardest part was centering the holes. The work piece is a little cumbersome and I had difficulty getting it positioned well as you can tell by my off-center holes. Others with more experience will likely produce better results.
As I mentioned in the engine bay walk through, the headlight header bar was in pretty bad shape. In addition to the considerable corrosion, there was also the issue of some improperly tapped holes. I had placed these holes in the header bar a few years earlier when I replaced the broken vacuum relays. The original mounting bolts twisted off and I did my best to put the new holes where the original were, but anyone that has reached up there knows how tight that space is, especially with a drill in your hand. Finally, I decided not to powder coat this piece because of the reinforcement plates. These are spot welded to the bar where the light buckets mount, and mine were a little swollen from the rust between them and the bar. I knew I could never blast all that rust out or get the powder in there, so I turned to trusty Zero-rust. It's supposed to bind with the rust and stop it from spreading. We'll see how well it works.
Headlight Header Bar Repair