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Bodywork question - rivet "bumps"
Thread Starter
Safety Car
Joined: Aug 2005
Posts: 3,654
Likes: 0
From: Chandler Arizona
St. Jude Donor '08
Bodywork question - rivet "bumps"
I know this topic has been debated somewhat but I have a specific question I can't find answers to. I am following the guidance on the Lars bodywork basics tech tips. As I have been sanding the front end down (decided to use sanding method on front clip) I noticed that you could tell where the rivets were in front of the hood. However, after going over the front end with 80 grit I have found that this area smoothed out nicely without leaving noticable bumps. In fact, the bumps came out w/o getting down to the gel coat. My question is: do I have to do anything other than proper priming/sealing in this area before paint? The car is now in a dry climate (AZ) and I wonder if it would ever come back? Or do I need to get them out of there and do the extra body work? Thanks 
Melting Slicks
Joined: Jan 2006
Posts: 2,664
Likes: 1
From: Nashville TN
I would think you need to address the issue now before spending so much money painting the car and having them come up again in a few years. From what I understand the rivets themselves are having a chemical (???) reaction and getting build up on them sorta like rust (???) and its causing the humps/bumps in the front. Even if you sand them down now I think I have read that they come back after time.
I guess it comes down to what your doing, if your building a daily driver and want to skimp on cash now and go with what you got you can and it would probably be okay for a year or two but it will come back. If your putting some serious hard earned money into your paint job it would be terrible not to spend the extra to fix it right and then you wouldnt have to worry about it.
I think DrRebuild addresses these rivets and the bumps in good detail but I cant find the link at the moment.
Good luck with it! I have to do the same thing in a few months and dont even know how to start addressing the problem.
I guess it comes down to what your doing, if your building a daily driver and want to skimp on cash now and go with what you got you can and it would probably be okay for a year or two but it will come back. If your putting some serious hard earned money into your paint job it would be terrible not to spend the extra to fix it right and then you wouldnt have to worry about it.
I think DrRebuild addresses these rivets and the bumps in good detail but I cant find the link at the moment.
Good luck with it! I have to do the same thing in a few months and dont even know how to start addressing the problem.
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
No matter what you do there is some risk of those holes becoming visible again as either lumps or sink holes. The bumps are caused by galvanic corrosion between dissimilar metals, aluminum rivets and the steel reinforcement below. Electrolytes in the atmosphere keep the corrosion active. And the steel reinforcement is probably rusty as well after all these years. I don't think there is enough room to get in there and seal off the reinforcement area and stop the galvanic corrosion. 1. You could prime and block sand the surface as is, but the lumps will eventually come back. 2. You can drill out all of the rivets, remove the reinforcement, install a new rust free reinforcement by gluing it to the fiberglass like the newer models, but you'll need to fill all of the holes and the filler will shrink in time leaving sink marks. 3. The most expensive would be section a new headlight panel in place and glue new bonding strips and reinforcement underneath, thus eliminating the holes and rivets. The second method is probably the best choice but you'll need extra hands. 
Thread Starter
Safety Car
Joined: Aug 2005
Posts: 3,654
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From: Chandler Arizona
St. Jude Donor '08
That sounds like a lot of work but since I'm doing a frame-off I guess it's just one more thing to do. I'm trying not to cut any corners. I'm replacing almost every nut and bolt, so I'd hate to try and take a short cut I would regret 2 yrs from now. What if I drilled them out and used duraglas to refill (short strand fiberglass filler)? That wouldn't shrink, would it?
Drifting
Joined: Feb 2005
Posts: 1,438
Likes: 2
From: Melrose Florida
Couple things: Original fiberglass does not have "gelcoat", it appears that you're into the fiberglass in a few areas.
The rivets hold bonding strips to the metal header bar, then the header bar is bonded to the underside of the hood surround.
THERE IS NO EASY WAY TO ADDRESS THIS.
The previous poster was correct about the corrosion, and that it often includes a rusted header bar.
My suggestion is to do just what you've already done, and repaint. The only other way to fix it right is with a new pressmolded hood surround ($1000 parts only).
In all honesty, I'm taking a slightly different approach, but my front end is disassembled. The header bar had been rmoved, and the rivet heads were corroded, but they hadn't bumped up on top. The header bar is in good shape. I used a grinder on the rivet heads and old bonding surfaces, used Fusor 147 adhesive, AND used rivets through the hood suuround and header bar. I'll try and grind these rivet heads down enough on the top to hide with filler.
Good luck.
Steve
The rivets hold bonding strips to the metal header bar, then the header bar is bonded to the underside of the hood surround.
THERE IS NO EASY WAY TO ADDRESS THIS.
The previous poster was correct about the corrosion, and that it often includes a rusted header bar.
My suggestion is to do just what you've already done, and repaint. The only other way to fix it right is with a new pressmolded hood surround ($1000 parts only).
In all honesty, I'm taking a slightly different approach, but my front end is disassembled. The header bar had been rmoved, and the rivet heads were corroded, but they hadn't bumped up on top. The header bar is in good shape. I used a grinder on the rivet heads and old bonding surfaces, used Fusor 147 adhesive, AND used rivets through the hood suuround and header bar. I'll try and grind these rivet heads down enough on the top to hide with filler.
Good luck.
Steve
Thread Starter
Safety Car
Joined: Aug 2005
Posts: 3,654
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From: Chandler Arizona
St. Jude Donor '08
Thanks Steve. So I guess this means I just have to hope it doesn't come back? Will the fact that it's in a dry climate now (AZ) and just a "weekender" help keep it from coming back as quickly?
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St. Jude Donor '09
Melting Slicks
Joined: Jan 2006
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From: Nashville TN
Some guy was trying to tell me that on the NCRS restored cars they actually look for the rivet bumps and knock points if you dont have them or they dont recommend fixing them or something like that? It was one of my new found neighbors that started coming around since I started working on my vette.
Melting Slicks
Joined: Dec 2000
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From: Lansdale 19446 PA
2024 C3 of the Year Finalist- Unmodified
St. Jude Donor '10-'11, '15, '19
I am NOT looking forward to that job!
My 69 looks like it has PIMPLES too! I thought about just removing the old rivets, popping in new rivets and patching the recesses. Never considered removing the header bar! YUCK!
I guess the good news is - ALL OF YOU! There will be plenty of support when I get to it next year. The 78 is first in line!
My 69 looks like it has PIMPLES too! I thought about just removing the old rivets, popping in new rivets and patching the recesses. Never considered removing the header bar! YUCK!
I guess the good news is - ALL OF YOU! There will be plenty of support when I get to it next year. The 78 is first in line!
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
You can certainly drill out the rivets and re-rivet the old header bar.
This is easiest if the car is assembled. In order for the filled holes to remain
flat, you must go over the new rivets with fiberglass ... not filler.
With the rivets corroded, the header bar is likely compromised with rust.
If body is off - bite the bullet and pull the header bar. You don't need to
rivet it back on ... just use a good adhesive on a clean header bar.
While you are at it (headlight assemblies out), you might as well refurb
the front reinforcement where the front of the assemblies bolt up.
... just my opinion. Oh yeah - much easier with the front clip upside-down.
This is a 75 ... no rivets to begin with.
http://nhvette.homeunix.com/ftp/_pic...nosedone_1.jpg
http://nhvette.homeunix.com/ftp/_pic...nosedone_2.jpg
This is easiest if the car is assembled. In order for the filled holes to remain
flat, you must go over the new rivets with fiberglass ... not filler.
With the rivets corroded, the header bar is likely compromised with rust.
If body is off - bite the bullet and pull the header bar. You don't need to
rivet it back on ... just use a good adhesive on a clean header bar.
While you are at it (headlight assemblies out), you might as well refurb
the front reinforcement where the front of the assemblies bolt up.
... just my opinion. Oh yeah - much easier with the front clip upside-down.
This is a 75 ... no rivets to begin with.
http://nhvette.homeunix.com/ftp/_pic...nosedone_1.jpg
http://nhvette.homeunix.com/ftp/_pic...nosedone_2.jpg
Thread Starter
Safety Car
Joined: Aug 2005
Posts: 3,654
Likes: 0
From: Chandler Arizona
St. Jude Donor '08
Jughead, thanks for the link. I never found this one in my advanced search.
So at the end of the day it seems there is still debate on the best way to go. Even though I have a matching motor/trans in my '69 I really don't give a hoot about NCRS points, or anything like that. I'm not a big show guy, more of a cruise night guy. No judging or awards, just show up when you want and leave when you want. This may mean that the best way to tackle this problem for me is to get them out of there for good and bond the header strip back on. I'm thinking that short strand fiberglass filler (the stuff Lars recommends) would keep the shrinking problem at bay.
Has anyone out there drilled out and filled theirs? Is it holding up?
So at the end of the day it seems there is still debate on the best way to go. Even though I have a matching motor/trans in my '69 I really don't give a hoot about NCRS points, or anything like that. I'm not a big show guy, more of a cruise night guy. No judging or awards, just show up when you want and leave when you want. This may mean that the best way to tackle this problem for me is to get them out of there for good and bond the header strip back on. I'm thinking that short strand fiberglass filler (the stuff Lars recommends) would keep the shrinking problem at bay.
Has anyone out there drilled out and filled theirs? Is it holding up?
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
There have been some posts lately warning of moisture absorption in
the fiberglass reinforced fillers. It's not much different to just fill them
with some chopped fiberglass strands and polyester resin. Yeah - it will
take several layers to build it up - but it's really not much work.
the fiberglass reinforced fillers. It's not much different to just fill them
with some chopped fiberglass strands and polyester resin. Yeah - it will
take several layers to build it up - but it's really not much work.
