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Sunburn on inside of hood.

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Old 05-09-2013, 09:04 AM   #1
ohiovet
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Default Sunburn on inside of hood.

As a followup to the recently closed thread I am posting the following:

Picture is of a hood on a 65 Corvette a friend of mine owned. The line at the upper right is the blistered paint.
It started smoking in about 5 minutes but only blistered the bottom of the hood since I closed it when I smelled the burning paint.
I think the thing that contributes to the burning is the fact that bottom of the hood is semi-flat black. If it was high gloss it would tend to reflect the heat and possibly not blister the paint.
I have told a few "new" owners of Corvettes about this and a few have ignored it and paid the price.

I currently own the car.

Click the image to open in full size.
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Old 05-09-2013, 09:33 AM   #2
Frankie the Fink
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I'm amazed at the people that scoff at this problem and think it's a myth. They need to go back to 8th grade science class. I've admonished owners at shows about this but have been ignored so I just walked. I use one of the vendor's cloth covers with elastic for this purpose (a little expensive). I used to just use a towel folded up but I would find them blown down in the engine bay on a breezy day and no help.
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Old 05-09-2013, 09:35 AM   #3
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I leave the hood closed.
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Originally Posted by Frankie the Fink View Post
I'm amazed at the people that scoff at this problem and think it's a myth. They need to go back to 8th grade science class. I've admonished owners at shows about this but have been ignored so I just walked. I use one of the vendor's cloth covers with elastic for this purpose (a little expensive). I used to just use a towel folded up but I would find them blown down in the engine bay on a breezy day and no help.
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Old 05-09-2013, 10:04 AM   #4
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Frankie,
I agree with your comments, in summary some people are to stupid to take good advice. I to have been ignored a number of times.
Here in So. Ohio, the land of clouds and rain it still happens.
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Old 05-09-2013, 10:36 AM   #5
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This is a real problem for all years that have a chrome air cleaner. The sun will reflect off them to a concentrated prism point and WILL burn and blister the paint both under the hood and, sometimes, through to the outside of the hood.
No problem in my case since my 65 has an LS3 with the black plastic intake so no reflection.
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Old 05-09-2013, 11:06 AM   #6
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I NEVER would have thought about this. While I don't show my car I do work on it with the hood open outside sometimes. The things I learn here!!!
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Old 05-09-2013, 11:31 AM   #7
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I know this has been discussed to death but...
I take my car to local shows and leave the hood open for hours at a time in the hot Miami sun. Ive heard these stories and wasnt sure so one time I took my IR thermometer and took some measurements (yes, some people looked at me kind of funny but Im use to that LOL). Anyway, I registered about 7* hotter wherever the sun was focused by the chrome. Not hot enough to do anything but made me realize that under the right conditions, the sun could be focused and do some damage. I now use one of the cloth beanie with the elastic trim and cross flags logo. Not a complete solution because the ignition cover also reflects. Cap Looks good not as good as shinny chrome but gives me piece of mind. Just got to remember to pull the cover before the judges come by
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Old 05-09-2013, 11:40 AM   #8
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Its only a problem with chrome air cleaner that have concave tops. The CI flat cover can be a problem when the retainer nut is snugged down tight. A cover with a concave center with the rest convex can be a problem.

Convex covers diffuse the sunlight rather than concentrate it. I think I learned this is 6th grade science class.


I have had people walk by my car at car shows and inform poor ignorant me, with his convex cover, that the hood will burn. It hasn't, won't ever, and I guess they flunked 6th grade science class, because they don't even want to hear why it won't.

Doug
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Old 05-09-2013, 01:12 PM   #9
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Quote:
Originally Posted by SLWRNU View Post
This is a real problem for all years that have a chrome air cleaner. The sun will reflect off them to a concentrated prism point and WILL burn and blister the paint both under the hood and, sometimes, through to the outside of the hood.
No problem in my case since my 65 has an LS3 with the black plastic intake so no reflection.
I saw it happen on a midyear at a show years ago, but was horrified when it happened to my silver '63 Split Window at a hot show in July. Wasnt worth the $10 trophy... at least the insurance company didnt think so, trying to match Sebring Silver.

Last edited by Vettebuyer6369; 05-09-2013 at 07:07 PM. Reason: typo on year
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Old 05-09-2013, 01:32 PM   #10
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I am now a believer. It happened to me yesterday with my 65.
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Old 05-09-2013, 01:55 PM   #11
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This has been an issue since the cars were new; folks who scoff at it simply don't understand basic physics.
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Old 05-09-2013, 03:07 PM   #12
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I wonder if a shower cap would work? They are pretty cheap.
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Old 05-09-2013, 03:54 PM   #13
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Quote:
Originally Posted by Revfan View Post
I wonder if a shower cap would work? They are pretty cheap.
Maybe one for an alien like ET, those air cleaners are 15"+ wide
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Old 05-09-2013, 05:30 PM   #14
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A piece of cardboard or plastic with a hole in the center to put under the wing nut would work. You could even use something with a logo.
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Old 05-09-2013, 06:04 PM   #15
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If I'm understanding this, it's the concave area under the wingnut that's causing the problem. Why not just put a flat washer (chromed or stainless) under the wingnut?
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Old 05-09-2013, 06:07 PM   #16
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Quote:
Originally Posted by RatDog View Post
If I'm understanding this, it's the concave area under the wingnut that's causing the problem. Why not just put a flat washer (chromed or stainless) under the wingnut?
Not entirely the case....its the air cleaner itself that distorts when the nuts are tightened down...not just the dime sized area under the wing nut.
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Old 05-09-2013, 06:17 PM   #17
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Yes, the 15" diameter c1 air cleaner, when the nut is tightened down, turns into a 15" diameter parabolic mirror with a focal length of about 80" (estimated), what this means is you get a 3"-4" wide focused spot under your hood (hood up, when reflection is at top edge of hood), that focus spot has about 6 times the sunlight/heat concentrated on it as compared to a 15" wide reflection from a flat surface.

Doug
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Old 05-09-2013, 06:58 PM   #18
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Quote:
Originally Posted by MikeM View Post
Gee, all this micro managing the problem.

I would have thought:

a) the reflection of the sun caused the problem

b) opening the hood with the sun at the wrong (right) angle

c) an overpolished C1 air cleaner

were the primary causes!
And thats why I do not run one!
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Old 05-09-2013, 07:14 PM   #19
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Regarding the angle, you can never be safe because the sun continues to move. When it happened to me, my car was sitting in the same spot for hours, but happened over a short period of time later in the day. See the picture in the OP? That's typical, as you get a straight line following the way the sun moves; mine looked just like that, with a corresponding straight bubbled line on the hood surface paint.

Mine was a '63 so I think any model with a chrome/polished air cleaner could result in this.

I bought one of those black canvas air cleaner covers with the elastic around the edge, with a Corvette logo on it. Looks nice and neat at a show and I think it was about $30. Ive used it on C1 and C2 cars.
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Old 05-09-2013, 07:25 PM   #20
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Quote:
Originally Posted by MikeM View Post
Gee, all this micro managing the problem.

I would have thought:

a) the reflection of the sun caused the problem

b) opening the hood with the sun at the wrong (right) angle

c) an overpolished C1 air cleaner

were the primary causes!
Well, no.

If the c1 air cleaner was perfectly flat, and it was 100% reflective (which it isn't), allowing the sun to reflect off the air cleaner onto the underside of the hood would not be any different that taking the hood off and laying it on the ground upside down in direct sunlight.

That doesn't bubble paint.

Reflected light is less intense than direct sunlight, only concentrated reflected light is the problem.

Doug
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