Trunk replacement
July 10th, 2019, 06:35 AM
#1
Trunk replacement
I'm looking at getting this trunk pan from the parts place for my 71 convertible with the body braces, tank braces and the drop offs. My son and I are pretty confident that we can do this, but I have a couple of questions. The body is braced and off the frame so we can put a one piece in from the bottom. The quarters have rot, mainly behind the wheels and we aren't sure yet whether they can be patched or need to be replaced, same with the wheel houses. If this goes well we might attempt the quarters.
Do the braces go on before or after the floor is in? Can we put the drop offs in and do the quarters and possibly wheel houses later or should we just do the floor for now? Any best methods for measuring and marking to get the new one in the right place?
https://www.thepartsplaceinc.com/pro...-freight/10101
Really looking for any tips, links, videos that will help make this as trouble free as possible for first timers.
Do the braces go on before or after the floor is in? Can we put the drop offs in and do the quarters and possibly wheel houses later or should we just do the floor for now? Any best methods for measuring and marking to get the new one in the right place?
https://www.thepartsplaceinc.com/pro...-freight/10101
Really looking for any tips, links, videos that will help make this as trouble free as possible for first timers.
July 10th, 2019, 11:18 AM
#4
July 10th, 2019, 05:18 PM
#6
Rodney
Join Date: Jun 2011
Location: Houston, TX
Posts: 2,323
Dew:
I haven't done a full trunk floor replacement, but I have done a full floor replacement, outer wheel houses and the trunk drop-offs. Your biggest concern should be keeping everything aligned properly as you replace the rusty metal; i.e. not too high or low on one side or twisted, etc. If you cut away too much old metal at one time you will lose your reference points and the new floor may not sit properly on the frame when you're finished. I would do the trunk floor first, then do the drop-offs once trunk is fully tacked in, then wheel houses and quarters (if you're still up to it)! Good job on bracing the body before separating from the frame, convertibles can easily twist without the strength of a roof.
When I replaced my floor I used a full pan from AMD that came with the braces and inner rocker panels. I used the existing car frame for my reference points. I removed the wheels and put the frame up on jack stands; I then shimmed the jack stands with blocks of 1/4" plywood to level the frame as my shop floor was not level. I cut eight 4x4 blocks, 12" long which I inserted between the frame and the body at all the body mount locations, this way the body was "indexed" to the leveled frame, just 12" higher. I had removed the engine and transmission so once the body was lifted, I could lay a long level across the frame in several places to double check the levelness. Then I cut away the old floor and drilled out the factory spot welds. There are special flat-tipped drill bits for drilling out the spot welds that allow you to carefully drill through only one layer of metal. A normal drill bit has a 135 degree point, whereas the spot weld bit is virtually flat so you don't drill through the 2nd layer.
I had to trial fit the new floor pan several times gently "massaging" and bending the metal each time until it fit snuggly. Each time, I removed and reinstalled the 12" blocks to make sure the body mounting points were all still aligned to the frame (albeit, 12" higher). Make sure all the body mount locations are resting on the 4x4 blocks before you begin tack welding in the new trunk floor. It's also a good Idea to tack a each corner once and recheck the body mount locations to make sure nothing has moved before continuing on with the rest of the welds. If you have a wire feed MIG welder, you can replicate the spot welds using plug welds. I chose to drill through the surviving metal so I could see where all the factory spot welds were located. This also meant I was plug welding through the older metal and into the new metal for the strongest joints.
One word of caution if you decide to replace the quarters. I would not do this with the body lifted off the frame. The trunk floor is somewhat unseen, so if it's a little bit "off" it likely won't be visible, but it's crucial that the quarter panels line up properly and aren't twisted. I think it's safer to do these panels with the body bolted to a leveled frame, at least that is my plan when I'm ready to install my quarters. Here's a link to my build page that might give you some insight as to how these cars are put together. I hope my suggestions will be helpful to you and your son.
Rodney
https://classicoldsmobile.com/forums...ertible-57404/
I haven't done a full trunk floor replacement, but I have done a full floor replacement, outer wheel houses and the trunk drop-offs. Your biggest concern should be keeping everything aligned properly as you replace the rusty metal; i.e. not too high or low on one side or twisted, etc. If you cut away too much old metal at one time you will lose your reference points and the new floor may not sit properly on the frame when you're finished. I would do the trunk floor first, then do the drop-offs once trunk is fully tacked in, then wheel houses and quarters (if you're still up to it)! Good job on bracing the body before separating from the frame, convertibles can easily twist without the strength of a roof.
When I replaced my floor I used a full pan from AMD that came with the braces and inner rocker panels. I used the existing car frame for my reference points. I removed the wheels and put the frame up on jack stands; I then shimmed the jack stands with blocks of 1/4" plywood to level the frame as my shop floor was not level. I cut eight 4x4 blocks, 12" long which I inserted between the frame and the body at all the body mount locations, this way the body was "indexed" to the leveled frame, just 12" higher. I had removed the engine and transmission so once the body was lifted, I could lay a long level across the frame in several places to double check the levelness. Then I cut away the old floor and drilled out the factory spot welds. There are special flat-tipped drill bits for drilling out the spot welds that allow you to carefully drill through only one layer of metal. A normal drill bit has a 135 degree point, whereas the spot weld bit is virtually flat so you don't drill through the 2nd layer.
I had to trial fit the new floor pan several times gently "massaging" and bending the metal each time until it fit snuggly. Each time, I removed and reinstalled the 12" blocks to make sure the body mounting points were all still aligned to the frame (albeit, 12" higher). Make sure all the body mount locations are resting on the 4x4 blocks before you begin tack welding in the new trunk floor. It's also a good Idea to tack a each corner once and recheck the body mount locations to make sure nothing has moved before continuing on with the rest of the welds. If you have a wire feed MIG welder, you can replicate the spot welds using plug welds. I chose to drill through the surviving metal so I could see where all the factory spot welds were located. This also meant I was plug welding through the older metal and into the new metal for the strongest joints.
One word of caution if you decide to replace the quarters. I would not do this with the body lifted off the frame. The trunk floor is somewhat unseen, so if it's a little bit "off" it likely won't be visible, but it's crucial that the quarter panels line up properly and aren't twisted. I think it's safer to do these panels with the body bolted to a leveled frame, at least that is my plan when I'm ready to install my quarters. Here's a link to my build page that might give you some insight as to how these cars are put together. I hope my suggestions will be helpful to you and your son.
Rodney
https://classicoldsmobile.com/forums...ertible-57404/
July 11th, 2019, 07:43 AM
#7
Dew:
I haven't done a full trunk floor replacement, but I have done a full floor replacement, outer wheel houses and the trunk drop-offs. Your biggest concern should be keeping everything aligned properly as you replace the rusty metal; i.e. not too high or low on one side or twisted, etc. If you cut away too much old metal at one time you will lose your reference points and the new floor may not sit properly on the frame when you're finished. I would do the trunk floor first, then do the drop-offs once trunk is fully tacked in, then wheel houses and quarters (if you're still up to it)! Good job on bracing the body before separating from the frame, convertibles can easily twist without the strength of a roof.
.
.
.
Rodney
https://classicoldsmobile.com/forums...ertible-57404/
I haven't done a full trunk floor replacement, but I have done a full floor replacement, outer wheel houses and the trunk drop-offs. Your biggest concern should be keeping everything aligned properly as you replace the rusty metal; i.e. not too high or low on one side or twisted, etc. If you cut away too much old metal at one time you will lose your reference points and the new floor may not sit properly on the frame when you're finished. I would do the trunk floor first, then do the drop-offs once trunk is fully tacked in, then wheel houses and quarters (if you're still up to it)! Good job on bracing the body before separating from the frame, convertibles can easily twist without the strength of a roof.
.
.
.
Rodney
https://classicoldsmobile.com/forums...ertible-57404/
I though about something along the lines of snapping a chalk line across the centers of the mounting holes both directions, then use an awl or something to scratch the lines in underneath outside of the section being replaced to line up the new floor. I'm hoping we can weld all of the braces on before we put the floor in. If we get a rotisserie after we could put them on later easy enough tho. I've got a guy that will put quarters on for 1500-1700, but it would be nice to save that and accomplish it ourselves. I'm not sure yet if it is better to fix or replace them. He's got a nice MIG welder and just bought a TIG welder. We have the space and I think the tools to do this and he's good at fabrication so I think the trunk will be fairly straight forward. Tips like this is just what I was looking for, thank you.
July 26th, 2023, 11:00 AM
#10
Registered User
Join Date: Feb 2008
Location: Jacksonville, FL
Posts: 1,884
As said by CDrod, I believe the full trunk pan comes with the braces attached.
(They did on my '65 that I replaced)
The one issue that I had with the full pan was that it didn't fit into that car in one piece.
In order to get it all in you've have to remove the rear facia and slide it in from the back OR remove the quarters and drop offs as it's wider than the bottom of the quarters.
I'm not sure it's the same for 70's as '65's though.
(They did on my '65 that I replaced)
The one issue that I had with the full pan was that it didn't fit into that car in one piece.
In order to get it all in you've have to remove the rear facia and slide it in from the back OR remove the quarters and drop offs as it's wider than the bottom of the quarters.
I'm not sure it's the same for 70's as '65's though.
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