So a while back I drove nearly across state to pick up a decent hood as mine was shot! The entire front section (the one you can buy) was rotted like crazy as well as the typical places back near the hinges.
The new one I bought only have rust back at the hinge area and I figured Id document how I repair this stuff. I had it in mind as I repaired them, that I would do a little write up, so I wrote on the hood itself through out the repairs.
Here we go.
Here are the rusted sections.
Passenger side:
Drivers side:
So beginning with an over sized patch, I bent the flanges to match the hood. As you can see I dont have many fancy tools.
Both flanges bent down.
Here is the panel with both flanges. You can see I have not cut the rusted area out. I like to make my patches, get them cut as a finished patch, then scribe the patch directly on the area to be replaced. Its much easier to achieve a nice clean fit in this manner (most times)
I used a profile gauge here (cheap one from harbor Freight) but you do not really need it for such a small and simple part.
It is nice however when working that curve into the part while standing at the Shrinker / Stretcher. This way I dont have to check the part against the hood so often. (just makes for less wandering around the garage)
Notes!!!!
A little shrinking and stretching on the flange I made. As you can see by shrinking and stretching the flange in the right areas, you can match the profile gauge.
On the other end (witout the flange) youll have to hand form the curve a bit. But because only 6" (roughly) away, the flange is trying to hold the shape for you.
Here you can see I have the profile in an acceptable tolerance. (good enough for my junk)
Now cut the rot out! Be careful not to cut the inner structure if you can help it. Though you can always weld it again so.... But its best to try to leave it untouched.
Cut the spot welds with a spot weld cutter (Harbor Freight for like $5.00)
You will likely find all the junk under there, that has caused your rot! Clean it and treat it to prevent more rust (as much as possible)
Now is where you want to make sure you make a great fit. This will save you more work later.
Ill go into a bit of info here.
So there are a few things people think about the fit. Some people like to leave a bit of a gap. The idea behind this is that once you have ground off the weld that is proud (sticking above the surface) that you will then have some of the weld left between the two panels and it will be a strong weld.
There are a few things that can hurt you by doing this though.
1. If your welder is set up correctly and you have good penetration through the sheet metal, then there is no need for the "filler" between the the panels. This is because the material from both sides will essentially melt together when there is both good penetration and a nice close fit. Basically the 2 pcs become one when the melt together.
2. Warpage..... when there is a gap, that means there is slack for the two panels to draw closer to each other. No matter the thickness of the material, it WILL shrink. And it WILL shrink from all the way around your weld toward the cent of the weld. If you give excess gap, it allows the panels to move toward each other when they shrink. Of course this on a microscopic scale, but when added up by multiple tacks, you'll notice it and it will cause you problems.
Beyond that, the gap will require more filler wire. More filler wire means more heat. More heat means more warping.
So the idea here is to keep the heat to a minimum. Quick, small diameter..BUT HOT... tacks are desired. that sounds counter productive, but a nice HOT tack will penetrate well the first time and you will not have to go back for pinholes or re-weld once you have ground off the top of the weld to find out that it didn't actually penetrate well and was primarily just on the surface.
OK I shall continue with pictures... LOL
I like to use a punch to allow me to "plug weld" back to the original steel that the outer skin was spot welded to.
A few well placed holes will help very well!
Tack her in when you feel you are happy with the fit!
A nice flush fit will save you body work later of course!
Here I have roughly ground the top of the tacks off. Be sure to tack a few places, elt it cool, grind the surface of the weld off, and repeat!
After the whole seam has been welded, finish grins / file, etc.... However you prefer to get a nice flat finish.
Of course some beer is needed!
The otehr side was done in exactly the same manner!