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  #1  
Old 05-02-2023, 10:58 AM
schwemf schwemf is offline
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Default Metal finishing a low crown hood

I hope to metal finish this hood (1960’s vintage GM, steel, 20 gauge I’m guessing). This job is pushing my metal finishing abilities, so I’m posting my progress here so that hopefully wiser eyes can keep me out of trouble. I have more hours on this job than I care to admit.
IMG_20230501_164530044.jpg

I believe that something fell on the hood’s left side, just behind the left hood scoop. Or perhaps improper storage left something leaning and pushing down on the top of the hood and scoop. In any event, the top skin bent against the reinforcing frame, which I’m guessing also caused a large, oil canned area behind the left scoop and adjacent to the bend. In the pictures I’ve used a blue magic marker to show where this bend was (the thick red magic marker lines identify a low area according to the profile gauge; the thin black lines identify a high area; the blue line around the scoop simply warns me to stay away from this area with the shrinking disk).
IMG_20230501_164552406.jpg

Following advice from prior posts to this board, I used a torch to shrink along the bend, heating single spots just till the metal swelled before tapping down with a slapping spoon and using a wood block as a dolly (thank you Kent White). No color change or water quench. This removed the bend and “tightened up” the oil canning. The oil canned area still needs further “tightening” as it deflects too easily under moderate hand pressure. The other side of the hood is much firmer in this area.

At this point I should have created profiles (thank you Jaroslav), but instead fell back on my training that taught me "when you loose your way, start at a good contour and work towards the bad.” With the bend mostly addressed, I’ve started metal finishing at the front of the left side of the hood and am working towards the rear.

The front of the hood appears to have hand prints from being forced closed. The red magic marker shows these low areas. Following other posts to this board, I’ve used pry bars where I have access, and torch heat where I don’t, to raise the low areas. The front of the hood has a higher crown so torch heat worked well. Thank you again Kent White.
IMG_20230501_164538164.jpg

Jaroslav’s advice about using profiles has really helped me find my way. The black and red magic marker lines show the high and low areas respectively according to the gauges.
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File Type: jpg IMG_20230501_164606076.jpg (74.6 KB, 12 views)
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Mike Schweitzer
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Last edited by schwemf; 05-02-2023 at 11:30 AM. Reason: moving pictures into the text
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  #2  
Old 05-02-2023, 11:33 AM
Jaroslav Jaroslav is offline
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Mike, good progress. Show another picture from the other side where the reinforcements are.
You heat the place that rises and cool it with a wet cloth.
You do not have to worry. Arching will be reduced. Although it is high at the moment. Try it on a piece of scrap.
You leave it alone for a day or two and check again. It still works without you.
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Old 05-02-2023, 12:15 PM
blue62 blue62 is offline
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Reinforcement or bracing on the back side always make things more difficult.
Have a good look at the bracing and make sure it is not bent or twisted.
That can cause lots of headache. Looks like your doing a great job.
Thanks for posting the pictures...visuals always add so much info.
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Old 05-02-2023, 08:15 PM
schwemf schwemf is offline
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Thank you for your encouraging words.

Here are pictures of the back side of the hood. Plus, there's an reinforcement (?) down the middle of the hood, so a pry bar inserted in the hood latch area won't touch the top skin for the first seven inches, each side of the hood split.
IMG_20230502_162312850.jpg

IMG_20230502_184337651.jpg

IMG_20230502_184512141.jpg

The hood frame has been brazed at some time in its life, as one picture shows. Otherwise, it seems undamaged and is straight. The hood looked good when I assembled the front clip before doing this body work.
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Old 05-03-2023, 01:05 AM
Jaroslav Jaroslav is offline
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Give it time, something will be knocked out from below and something from above with heat.
Take breaks between steps. After balancing, it works by itself even when you are sleeping. The rest putty.
If there is a sharper bend, it is possible to drill a hole, level it and weld it again. But that needs to be thought through.
I think it should be settled. Try some steps on a scrap piece.
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Old 05-03-2023, 07:06 AM
schwemf schwemf is offline
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When I can't get behind the dent due to the reinforcement/bracing, I'm a bit undecided between which works best: heat from a torch or a stud welder.

Heating with a torch and immediately filing seems to only restore the contour briefly, while the spot is hot. Then it shrinks a bit as it cools creating a slight low.

I've used a stud welder to pull up the low area gently while tapping down around the surrounding high. I don't just give it a big pull, trying not to create a little mountains (so to speak). This works, but I don't like what the stud welder does to metal. The spot where the stud was welded now files like work hardened metal.
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Old 05-03-2023, 07:30 AM
Jaroslav Jaroslav is offline
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You can still drill or cut a hole in the reinforcement and then weld it again after straightening the bulge.
If you are straightening with a flame, and you need an upward direction, just heat it up and let it cool down. Follow the directions, you can lift it even from a place larger than it the this place. If it's warm, don't hammer it, leave it alone until it comes to room temperature.
If you need to reduce a bump, you heat it, the bumb gets bigger, it grows before your eyes, and you immediately cool it down.
Again, you don't hammer it, you let it cool down.
If you want to use a hammer, you can only do so when it is stabilized and at room temperature.
Try it on the scrap, it's the best textbook. Take your time, molecules need their time.
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Old 05-03-2023, 07:54 AM
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drivejunk drivejunk is offline
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Heres what I see...

That hood was once really ugly. Front corner damage on skin and shell came from a mailbox, pole, or sign hit or a left fender bender. What you have behind the scoop may be a resultant buckle which occured at the same time, or more likely it is where the sign or mailbox hit.

The brazing ought to be dug out and a proper weld made. Its a crack from the wreck. And I don't know that you'll get a nice fit if the skin and shell both get ironed out nicely due to the amount of stretching present.

Those things being said, I believe the trouble behind the scoop is in the bend at back of scoop. The angle was flattened out a bit by the damage so it urges the metal down.

I really like the idea of using the other side as profile reference. I suspect that the damage extends into the slotted area but... as with durn near every crown problem on a big panel... that the answer is at the edge of the panel. For example if you knock directly on a folded edge, it puts crown into the face well out past the edge. Small amounts of shell edge bent up or down or skin folded over too tightly have great effect on the panel face as well.

So at the back, I think the slotted area and bend at back of scoop are holding that low area down. You've straightened the gouge but not yet the areas around it which remember the damage.

Honestly, the issues at front merit replacement. The hood is worse off than you think, the damage was more severe than percieved due to the "save" already made. Cutting away a section of the shell might come into play if I tried to fix what you have there.

Happens all the time. Old repair makes better repair not viable.

As far as stud pulling, well I frequently do that as needed and in those situations, a fine filler free metal finish is out of the question. Ironing things out to make the filler as thin as you can is what to shoot for. Care during puller use, and during any following straightening is important. The idea is to only bump off dolly so no more stretching occurs.

Just my .02. I have one decade in collision repair and a dozen years in old car metal work, fab, and panel saves but am a novice shaper. You are repairing, not shaping new metal. Applying heat to panel faces is an "almost never" situation for me. Rarely is it applicable in my world and I have never tried a shrinking disc.
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Old 05-03-2023, 06:32 PM
schwemf schwemf is offline
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Quote:
Originally Posted by blue62 View Post
Have a good look at the bracing and make sure it is not bent or twisted.
Hello Dave,
You were right, as the right side hood bracing has three obvious damaged areas. I've already uploaded a shot of one of these areas, the spot that was brazed. Here are the other two.

IMG_20230503_152742542.jpg

IMG_20230503_153714219.jpg

Again, this is the right side of the hood and we've been discussing the left.

The left side bracing appears Okay. At least there's no obvious damage.
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Old 05-03-2023, 06:50 PM
schwemf schwemf is offline
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Quote:
Originally Posted by drivejunk View Post
So at the back, I think the slotted area and bend at back of scoop are holding that low area down.
Hello Matt,
I'm glad that you pointed this out, and you are correct in that these areas are low.

Plus, the weakest point of oil can is now at the rear outside edge of the scoop. I'm not sure what that's trying to tell me?

I'll focus on these areas and see if that helps the bent area return to its proper contour. Like you said, there's a prop (or two) somewhere holding this bent area down!
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Last edited by schwemf; 05-04-2023 at 08:44 PM.
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