Problem decklid

T

TAguy16

I have a decklid I'm really having a time with. I've restored a lot of vehicles in my day but this thing makes me feel like I've never done any metal/bodywork before when I see the results after painting. It's for an old Road Runner and when I got it it had a lot of stretched metal on it evidently from people stting on it or piling stuff on it. I shrank down all the stretched metal and pulled up the low spots with my stud gun, and of course after doing all this I was left with a big piece of out of wack metal. Since I couldn't work the metal from the back side like I prefer to do I broke down and got some "gold" filler to fill in the slightly low spots. None of it was more than about 1/8" thick after sanding it down that I can tell. I sanded the filler with 40 grit then 80 then 180 before applied epoxy to the low spots and spraying primer surfacer on it to block it out.

I've painted it several times - blocking it out again between painting with my long board - and each time I paint it it looks terrible - like I never did anything to it to try to straighten it (it's hard to tell from the picture I'm attaching). It's as if the filler underneath the paint keeps shrinking on me. Another possibility could be the metal itself has gotten damaged or fatigued from all that's been done to it to the point where it doesn't want to take a permanent set again and stay it one place. I always guide coat it between sandings and it always looks like it should be straight. This decklid has a small amount of dome to it, but on the ouside edges it actually curves up slightly the other way to match the top edges of the quarter panel which go back down in that area. This is really frustrating say the least not to mention a waste of material and time. I feel like I woud have been much better off removing the skin from the inner structure and rolling out a new one on my English wheel for all the work I've done to this thing.

I would apppreciate greatly any idea on things I could try to get this thing straight again.
 

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Was it sandblasted? It might be stretched from that. Also, the internal bracing can push against the metal and help create low spots from the block being able to push against the brace and incorrectly remove material. If it has several paint jobs on it you might need to get all that off and start fresh. Pay careful attention to any weak/oilcan metal, and check to see how the metal being supported by the internal bracing might be affecting results. On panels like that, sometimes you just have to play "Pong" with the sanding block, spending hours sending it across the panel with virtually no downward pressure. Obviously, when doing so you should stick with coarser grits and new, high quality sandpaper.
 
Yes, I believe it was blasted at some point, and who know what else. The oil canning you were referring to is the stretched metal I mentioned that I shrank with the shrinking attachment on my stud gun. There were a lot of low spots I tried to bring up with studs also. I don't like using body filler so I was trying to get it as straight as I could without that.

I agree the inner panel probably isn't helping matters. I think another problem is the body filler I used was pretty hard stuff so it doesn't sand as easily as the primer - as such it's easy for the filler to end up being the high spot since it resists the sandpaper while every thing around it gets taken down by the sandpaper when sanding. This is exactly why I avoid using filler like the plague (I don't even like having it around): it's a mess to use and in my opinion you're risking trouble down the road using it. I'm used to restoring really old vehicles that didn't have any inner panels to speak of so I've always been able to get at the back side of things to straighten panels without filler. That has worked out a lot better for me, even though takes a lot of time and patience to do it that way.
 
Been there before and I have solved the problem with either a shrinking disk and or torch and wet rang to shrink the metal.
 
Those relatively flat 60's panels are a whole different story from old fat fender stuff. It could be that you'd be money ahead finding a deck lid that hasn't been worked on, hard to say without looking around. I know I had a hood from a '70 Chevy pickup with a similar problem, it ended up being WAY better just to find another, but those are more plentiful.
 
If you do decide to repair, thin coats of a premium filler should be used, and start sanding them before they get rock hard.
 
I thought the "gold" filler WAS the premium filler - I know I paid a premium price for it :) . Back in the old days of using Bondo didn't they recommend "cheese-grating" it while it was still setting up to reduce the sanding?

The problem with the old Mopar decklids is they rust around the edges where the outer panel is crimped over the inner one so it's hard to find rust free ones. Desert Valley Auto in AZ claims to have some RR decklids that are rust free and straight but to ship one half-way across the country is very very expensive. Around the midwest they are virtually nonexistent.
 
A cheesegrater can be used for heavy applications, but that should be a pretty rare occurrence, like on a crappy car with little time to fix the metal right.. I like to use 40 grit to break the surface of the initial application of filler before it is totally hardened to level out spreader marks and knock down high areas. I think you have metal there that is pretty squirrelly, I like to think I am okay at metalwork, but on a flat panel like that that has been blasted and subsequently worked, I hate to say it, but i think you are in for more trouble...
 
A cheesegrater can be used for heavy applications, but that should be a pretty rare occurrence, like on a crappy car with little time to fix the metal right.. I like to use 40 grit to break the surface of the initial application of filler before it is totally hardened to level out spreader marks and knock down high areas. I think you have metal there that is pretty squirrelly, I like to think I am okay at metalwork, but on a flat panel like that that has been blasted and subsequently worked, I hate to say it, but i think you are in for more trouble...
You're probably right. Large flat - or almost flat - panels can be a big problem once the get seriously messed up. Curved panels seem to be more forgiving: I've brought back old curved fenders to show quality (the vehicles they got put on won or placed at car shows) that were literally thrown on a junk pile they were so bad just with metal work (no filler). I'm not saying this to toot my own horn but just to make a point how troublesome flat panels can be when they get seriously damaged.

Like I mentioned earlier I wish I would have just started from scratch with new metal. It's a lot of work fabricating large panels from scratch, but I think in the long run it would have been better to do this.
 
I agree with Crash there are times when you just have to look for a replacement, even a re-pop part could take less time to make perfect. the time you want to put into a part is up to you but if I can save time getting a new part it just makes since to do that especially when time is money.
 
If the steel is compromised, is it possible the stand (assuming it was on a stand) was distorting the surface of the panel when sanding? Maybe work the panel on the car???
 
I'm wondering if a spray-on polyester primer/filler like Slicksand would be a good option since I'm not trying to fill in deep dents here and there but rather minor ripples and low spots all over. I haven't used this for a while but if memory serves these build up better than 2K but still sand fairly easily.
 
If the steel is compromised, is it possible the stand (assuming it was on a stand) was distorting the surface of the panel when sanding? Maybe work the panel on the car???
I'll give that some thought. It's resting on the outer surfaces of the inner panel in spots where it drops down away from the outer panel and forms channels (I'm assuming to add strength and stiffness) so it's sitting on pretty stout metal. This decklid has to weigh well over 50 pounds, and most of that weight taken up by the inner panel. Chrysler sure didn't skimp on metal back then!
 
I'm wondering if a spray-on polyester primer/filler like Slicksand would be a good option since I'm not trying to fill in deep dents here and there but rather minor ripples and low spots all over. I haven't used this for a while but if memory serves these build up better than 2K but still sand fairly easily.

Polyester is definitely a good option IMO! Super build, minimal shrinkage and sands great! That said, You may even have enough material on there now to block it out?? I'm with you on flat surfaces... They're a PITA!!!
 
Polyester is definitely a good option IMO! Super build, minimal shrinkage and sands great! That said, You may even have enough material on there now to block it out?? I'm with you on flat surfaces... They're a PITA!!!
I tried blocking it out with all I've got on there now but the paint doesn't want to sand at all with either 180 or 80 grit. I decided to take it down (with a stripping disk) to the where I have all primer surfacer as much as I can. I think part o f my problem is that I'm not sanding material that sands easy enough (or I have material the sands easy right next to that which doesn't) and I'm not able to get it straight since the material that doesn't sand easy doesn't come down as fast as that which does. I'm going to reblock what's left of that out then decide what to do - whether to go with the poly primer or more 2K.

I'm really liking the Norton Rapid Strip disks I got. They really can remove a lot of hard material in a hurry, and they don't seem to gouge the metal if you get down to bare metal with them like coarse sandpaper on a grinder does. I'm using them on my electric polisher. You have to be very careful to keep them moving (don't stay in one spot too long) or they may warp the metal because of building up heat from all the friction.
 
Poly primer was mentioned as an option, which sounds great at first because of the high build, but it might cause more trouble since most poly primers are pretty hard to sand. Maybe there are some out there that are easy, but I don't know of any. I think what's needed here are easy to sand products, coarse grits, literally next to no pressure on the block while sanding, and tons of patience.
 
Poly primer was mentioned as an option, which sounds great at first because of the high build, but it might cause more trouble since most poly primers are pretty hard to sand. Maybe there are some out there that are easy, but I don't know of any. I think what's needed here are easy to sand products, coarse grits, literally next to no pressure on the block while sanding, and tons of patience.
I tend to agree with you about needing easy sanding of whatever products I use so I don't have to put much downward pressure on the decklid to remove material. Also the easier sanding products seem to sand better with 180 grit and finer sandpaper than they do with coarser paper so you don't have to worry about having to remove deep sand scratches on top of everything else before sealing the surface.
 
What I find is that when sanding these types of panels by hand it is really tough not to apply too much pressure on the panel. Even a slight flexing will cause you headaches.
I use a Hutchins Air File (inline sander) in such cases. A coarse grit (36 - 40) like crash said is best for getting panel flat and straight. Simply let the weight of the sander be all the pressure that's applied to the panel and change the paper as soon as it stops cutting. You actually will feel like your wasting sandpaper if you are changing it often enough.
Guide coat is your friend in these situations as it will keep you from sanding too much material off. Once straight spray some more poly primer, guide coat and do it again with 180 grit. At this point you should be good to go with 2k.
 
The first thing you need to do if you want to salvage this panel is to strip it down to metal. Start over. Look at it, study it. See what is going on. If its oil canning it could be stretched or it could be oil canning from you shrinking an area too much. This is a oversimplification but if it is doming that would indicate stretching. If it is sinking near an area that you shrunk that would indicate overshrinking. Doming type stretching you need to do a series of gentle shrinks. Using the stud gun shrinker and cooling it is the worst way to shrink a panel. Quenching it work hardens the metal. Try using a torch or heat the area with the stud gun and use light hammer blows to shrink it. You can back it up with a dolly but is is not actually neccesary to do so. Overshrinking an area can be corrected by hammering on dolly. This will stretch the affected area and bring it back up. Work the metal to repair it, filler should only be used when you correct the problem(s).
I would argue that using a inline sander on a loose panel is much harder than a long block (17 inches+) Not trying to be harsh, but judging by your comments this is honestly probably way above your skill level to repair. If you want to learn keep working at it, if you are simply trying to get a decklid painted then I would begin the search for a replacement.
 
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