How to Install a Trunk Floor in a 1957 Chevrolet Bel Air

No Junk In The Trunk - We install a mini-tub trunk floor in a '57 hardtop for a solid trunk and more room for tire.

Patrick Hill Apr 23, 2014 0 Comment(s)
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When we started working on this '57 hardtop in the 2013 issue of Chevy Classics, it had been sitting for almost 20 years, as its owner tried to figure out a course of action for fixing its solid but hacked up floor and firewall from a previous owner's butchering. Thanks to the ever-growing Tri-Five Chevy parts market and Classic Industries, instead of a complicated series of patches involving metal fabrication, we were able to install a brand-new, one-piece floor and firewall, solving most of this car's ills. That just left the trunk floor.

The plans for this '57 involve bolting it to an aftermarket chassis of some sort, stuffing in the baddest LS motor the owner can build, and turning the hardtop into a monster Pro Touring machine. To achieve this, we knew at least a 315-width tire would have to be installed out back. This meant mini-tubbing. So, the fairly solid trunk floor was gonna need to be modified, along with repaired, because of rust in the floor and the tailpanel area. Once again, Classic Industries provided the perfect answer: its deep-well trunk floor, which comes pre-narrowed for a mini-tub installation.

Even though it took a little more work than the passenger floor, the trunk unit went in fairly easily, and the fit was perfect. In this story, we're going to cover getting the floor in place and ready, so in the next installment we can measure and cut for the mini-tubs, weld them in, weld the floor in place, and finish up by installing the tailpanel. Once done, our '57's body will be as good as new—with all-new metal from the firewall to the trunk—and ready for us to begin the next phase of the project.

Classic Industries Parts List
Tailpanel – TF400652
Deep Tub Trunk Floor – TF400952

1957 Chevrolet Bel Air Trunk 2/23

1 Here's what we started with. Overall, our trunk floor wasn't in bad shape, but the metal on the passenger side was a bit thin with a couple of pinholes, and back by the tailpanel and tail brace, there was some rust.

1957 Chevrolet Bel Air Stock Wheel 3/23

2 One of the reasons we're doing this install is to make room for a mini-tub modification, so we'll be able to stuff at least a 315-size tire in the back. With the stock wheeltubs, this is impossible.

1957 Chevrolet Bel Air Remove Old 4/23

3 The first step in removing the floor was using a MAP gas torch to melt away all the old paint, Bondo, and lead on the seam between the tailpanel and taillight-area metal.

1957 Chevrolet Bel Air Tailpanel 5/23

4 Once we started digging, we realized the car's original tailpanel was badly rusted out, along with the tailpanel brace underneath it. This is a normal area for rust on Tri-Five bodies, as it's a collection point for water running down the back of the car.

1957 Chevrolet Bel Air Cut 6/23

5 Using a Sawzall, we cut inside the tailpanel seams to remove the panel. We'll go back later and drill out the spot welds holding the end pieces to the rest of the body and prep them for a new tailpanel install.

1957 Chevrolet Bel Air Tailpanel Brace 7/23

6 Under the tailpanel, we found serious rust damage to the tailpanel brace. Fortunately, the new trunk floor comes with the brace already installed. If all you need is the brace, Classic Industries sells it separately.

1957 Chevrolet Bel Air Cut Floor 8/23

7 To make things easier, we started to use a Sawzall to cut out sections of the floor.

1957 Chevrolet Bel Air Plasma Cut Trunk 9/23

8 After a little bit of fighting to get the Sawzall into certain angles, we pitched that and grabbed our plasma cutter and used it to carve up our old trunk floor. The plasma cutter made quick work of it.

1957 Chevrolet Bel Air Trunk Floor 10/23

9 After about 30 minutes of cut-ting, here's where we stood. We stopped short of the factory shock mounts because we'd need to do some more delicate work to get that section removed.

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