C3 Headlamp header "pimples"

[Richard M.]

Looking for suggestions on repairing the 'pimples' caused by the headlamp header panel rivets oxidizing on my '68. Looking to hopefully repair from the bottom by drilling out rivets & re-bonding panel.
Looking for suggestions that would keep original paint intact.
Thanks

[Joe L.]

Re: C3 Headlamp header "pimples"

Looking for suggestions on repairing the 'pimples' caused by the headlamp header panel rivets oxidizing on my '68. Looking to hopefully repair from the bottom by drilling out rivets & re-bonding panel.
Looking for suggestions that would keep original paint intact.
Thanks

Richard------

Unfortunately, this is a fairly common problem on 1968-72 Corvettes, especially those that have lived in "salted road" areas of the country.

Many years ago, the late Ralph Eckler, a fiberglass expert, wrote a wonderful article for Vette Magazine on repair of this condition. I have that magazine here someplace but don't really have the inclination to dig it out right now. I'd need to go through a whole lot of past editions to find it.

In any event, the repair is nothing like you propose and would definitely require a repaint after the repair is done. I would opine that doing it as you propose and without damaging the paint is an absolute impossibility.

[Mark E.]

Re: C3 Headlamp header "pimples"

http://www.docrebuild.com/dr-r-web/tip18.html

[Thomas H.]

Re: C3 Headlamp header "pimples"

Another way to look at those bumps is you probably still have the original nose area - sort of a badge of honor .

My 71 LS5 has them and I use that rational to justify their existence (at least until the day comes that I restore the car.........)

When the time comes to restore the car I don't know which way I'll go - rivets or bonding. Since the car will end up being judged, I may do something that is a mix of both.

Tom

[Patrick B.]

Re: C3 Headlamp header "pimples"

I think there is a way to solve the rivet corrosion bumps without messing up the paint but it would be quite laborious. However, with paint jobs costing $10k to $20k, it could be worth the trouble for an owner who is a good mechanic and has sufficient hate of these bumps.

The paint risk occurs when you try to separate the bonding strip that is riveted to the headlamp support bar from the front surround panel with putty knives, wedges, etc. If you can leave this bonding strip in place, but remove the rivets from it from the steel support bar side you have eliminated the risk to the paint job. With the rivets and corrosion deposit removed, the bumps are said to go away if the car is placed in the hot sun for a week or so.

As with any good method of attacking the bumps, the grills, head lamp doors and all the mechanisms attached to the steel support bar must be removed. This would be a real pain. Also, it may be necessary to remove the radiator and radiator support for working room, but I hope not.
With the area cleared, knock the peened ends of the rivets off the steel support bar. Make a collar for a drill bit the size of the rivet hole to allow the drill bit to penetrate only thickness of the steel support bar. Drill the rivet material out of the steel support bar, and it should fall off the bonding strip. Now the bonding strip and the rivet shafts are exposed. Get a spot weld cutter the diameter of the rivet head (about 1/2"). These things look like a tiny hole saw with a spring loaded center pin which would fit in the recess of the drilled rivet shaft. Make a stop collar for the spot weld cutter to limit its cutting depth to the thickness of the bonding strip, so it won't touch the surround panel. Use the cutter to remove the small circle of bonding strip behind each rivet head, and remove the rivet and corrosion product. After the bumps have settled down, the steel support bar can be bonded to the bonding strip (which is still bonded to the car) using a modern steel to fiberglass adhesive like the 73 up C3's. I think it is called Fuser from the Lord company.

I have thought about this process, but I have not done it yet. I may get part of wrecked surround panel to test it.

[Richard M.]

Re: C3 Headlamp header "pimples"

I think there is a way to solve the rivet corrosion bumps without messing up the paint but it would be quite laborious. However, with paint jobs costing $10k to $20k, it could be worth the trouble for an owner who is a good mechanic and has sufficient hate of these bumps.

The paint risk occurs when you try to separate the bonding strip that is riveted to the headlamp support bar from the front surround panel with putty knives, wedges, etc. If you can leave this bonding strip in place, but remove the rivets from it from the steel support bar side you have eliminated the risk to the paint job. With the rivets and corrosion deposit removed, the bumps are said to go away if the car is placed in the hot sun for a week or so.

As with any good method of attacking the bumps, the grills, head lamp doors and all the mechanisms attached to the steel support bar must be removed. This would be a real pain. Also, it may be necessary to remove the radiator and radiator support for working room, but I hope not.
With the area cleared, knock the peened ends of the rivets off the steel support bar. Make a collar for a drill bit the size of the rivet hole to allow the drill bit to penetrate only thickness of the steel support bar. Drill the rivet material out of the steel support bar, and it should fall off the bonding strip. Now the bonding strip and the rivet shafts are exposed. Get a spot weld cutter the diameter of the rivet head (about 1/2"). These things look like a tiny hole saw with a spring loaded center pin which would fit in the recess of the drilled rivet shaft. Make a stop collar for the spot weld cutter to limit its cutting depth to the thickness of the bonding strip, so it won't touch the surround panel. Use the cutter to remove the small circle of bonding strip behind each rivet head, and remove the rivet and corrosion product. After the bumps have settled down, the steel support bar can be bonded to the bonding strip (which is still bonded to the car) using a modern steel to fiberglass adhesive like the 73 up C3's. I think it is called Fuser from the Lord company.

I have thought about this process, but I have not done it yet. I may get part of wrecked surround panel to test it.

Thanks Patrick, That's the type of process I'm considering. I have a bulletin from Willcox Corvette doing something similar & was curious if anyone else has tackled the job with success.
Haven't completely decided if I'll attempt, since it's an unrestored car. Don't know if I'll ever have judged, but everything I do goes in that direction for the next owner.
Thanks

[Joe L.]

Re: C3 Headlamp header "pimples"

I think there is a way to solve the rivet corrosion bumps without messing up the paint but it would be quite laborious. However, with paint jobs costing $10k to $20k, it could be worth the trouble for an owner who is a good mechanic and has sufficient hate of these bumps.

The paint risk occurs when you try to separate the bonding strip that is riveted to the headlamp support bar from the front surround panel with putty knives, wedges, etc. If you can leave this bonding strip in place, but remove the rivets from it from the steel support bar side you have eliminated the risk to the paint job. With the rivets and corrosion deposit removed, the bumps are said to go away if the car is placed in the hot sun for a week or so.

As with any good method of attacking the bumps, the grills, head lamp doors and all the mechanisms attached to the steel support bar must be removed. This would be a real pain. Also, it may be necessary to remove the radiator and radiator support for working room, but I hope not.
With the area cleared, knock the peened ends of the rivets off the steel support bar. Make a collar for a drill bit the size of the rivet hole to allow the drill bit to penetrate only thickness of the steel support bar. Drill the rivet material out of the steel support bar, and it should fall off the bonding strip. Now the bonding strip and the rivet shafts are exposed. Get a spot weld cutter the diameter of the rivet head (about 1/2"). These things look like a tiny hole saw with a spring loaded center pin which would fit in the recess of the drilled rivet shaft. Make a stop collar for the spot weld cutter to limit its cutting depth to the thickness of the bonding strip, so it won't touch the surround panel. Use the cutter to remove the small circle of bonding strip behind each rivet head, and remove the rivet and corrosion product. After the bumps have settled down, the steel support bar can be bonded to the bonding strip (which is still bonded to the car) using a modern steel to fiberglass adhesive like the 73 up C3's. I think it is called Fuser from the Lord company.

I have thought about this process, but I have not done it yet. I may get part of wrecked surround panel to test it.

Patrick------


If you try this method, I'll be very interested in how it works out. I'll be absolutely amazed if the original configuration of the body panel can be restored using this method regardless of how much care and effort is put into it. However, I like to be amazed so if this is such an opportunity, that's great.

By the way, my interest in this is strictly academic as my original owner 1969 does not suffer from this problem.

[Patrick B.]

Re: C3 Headlamp header "pimples"

Patrick------


If you try this method, I'll be very interested in how it works out. I'll be absolutely amazed if the original configuration of the body panel can be restored using this method regardless of how much care and effort is put into it. However, I like to be amazed so if this is such an opportunity, that's great.

By the way, my interest in this is strictly academic as my original owner 1969 does not suffer from this problem.

Joe-- My idea was not as original as I thought. I found several strings about this problem in the Corvette Forum, and at least two of the people offering info and pixs left the bonding strip in place and removed the rivets from inside by grinding or using a small hole saw. Also, the Wilcox article cited in this thread (Installing the Headlamp Support Header Bar) does the same thing by grinding out the rivets from inside. However, he cuts the steel bar into three pieces for removal which seems unnecessary.

[Kenneth B.]

Re: C3 Headlamp header "pimples"

I am with Joe. Don't think it can be done without painting. Seems like trying to fix from the underneath would cause more damage to the header bar & don't see how the paint will go back flat & adhere to the surface of what's left. But I guess never to say never. None of mine have had that problem although I have saw many with that condition.

[Paul S.]

Re: C3 Headlamp header "pimples"

There are 36 or so of those rivits . I have done several from the bottom side , ( pull headlight assemblies out and get the header bar out and dremil each of the rivits out carefully and you can do it without screwing up the exterior paint .then bond header bar back to the surround panel . It ain't easy but it can be done .

[Kenneth B.]

Re: C3 Headlamp header "pimples"

Then the paint bubbles go back flat & doesn't chip?

[Patrick B.]

Re: C3 Headlamp header "pimples"

Then the paint bubbles go back flat & doesn't chip?

Except in extreme cases, the fiberglass has risen gently but perceptibly at the rivets and there are no cracks in the paint. When what is pushing the fiberglass up has been removed, the glass will gradually return to straight with exposure to hot sunlight. I have seem pictures of people clamping boards to the top of the surround to accelerate the straightening but it is not necessary if one has time and patience.

[Kenneth B.]

Re: C3 Headlamp header "pimples"

Except in extreme cases, the fiberglass has risen gently but perceptibly at the rivets and there are no cracks in the paint. When what is pushing the fiberglass up has been removed, the glass will gradually return to straight with exposure to hot sunlight. I have seem pictures of people clamping boards to the top of the surround to accelerate the straightening but it is not necessary if one has time and patience.

So its the fiberglass that lifts not the paint. Guess I never made the connection Mr. Obvious.