Driver-Side Floorpan Replacement - Making It Pan Out
When the hard road deals your floorboard a death sentence of rust, you can easily replace it with a patch panel from Dynacorn.
From the October, 2012 issue of Popular Hot Rodding
By Johnny Hunkins
Photography by Johnny Hunkins
We were all set to finish the Art Morrison Enterprises rollbar kit in our ’68 Nova project car, counting the few days more it would be to have the interior completely finished for the summer cruise season, when we were dealt a cruel surprise by a previous owner: a driver-side floorpan full of rust. You’d think this would be easy enough to spot when buying a car, but our intrepid seller had artfully covered the rot with a thin layer of fiberglass, mudded it in with body filler, then camouflaged it with a can of truck bedliner to look like factory sealant. When the crew at Outlaw Motorsports used a grinder to smooth the surface in preparation for welding the rollbar mounting plates, the building filled with the acrid smoke of burning Bondo faster than you could say caveat emptor.
We were lucky to have Outlaw...
We were lucky to have Outlaw Motorsports to help us with the ’68 Nova’s floor patch panel replacement, but if you want to tackle it yourself, you better have a quality welder like Miller Electric’s Millermatic 211. This is the most critical tool you’ll need for the job.
The ironic thing is that the subterfuge of cloaking the hack job easily took as much time as fixing it the right way, which is what Outlaw Motorsports in Riverside, California, chose to do. The correct fix is to cut out the offending rust area, and replace it with a new patch panel, and that will be our mission here. Outlaw Motorsports is a direct dealer for Dynacorn sheetmetal for muscle cars, so it was only natural to check them first. We needed a partial left-hand floorpan, PN 1635, for ’68-74 Nova (actually called a “full” pan, but it’s really only for half the car). It was in stock at a nearby warehouse, the price was right at just $56, and they could deliver it the next day. We can count the times that’s ever happened before on just one hand. When we got our Dynacorn floorpan, it looked like a dead ringer for the stock one, and the fit ended up being very good with little massaging required. In fact, the whole operation took just three hours. If you want to see the video showing the entire operation, just go to www.YouTube.com/PopularHotRodding
and look for “Project Nova—Floor Patch Panel Repair.”
Thankfully, Dynacorn manufactures...
Thankfully, Dynacorn manufactures replacement floor panels for our Nova, and this one (PN 1635) fits all Novas built from 1968 to 1974. Dynacorn makes virtually every panel for second-gen Novas, so you’re well covered. Outlaw Motorsports in Riverside, California, is a Dynacorn dealer, and can cut you a swinging deal on your Nova, Camaro, or Mustang sheetmetal.
The fact that our Nova already had the interior out did make things easier, and Outlaw’s Ron Aschtgen says for a job like this he normally charges between $200 and $300, including the floorpan. If you want to do the job yourself, you’ll be happy to learn that it’s an easy one—perfect for the beginner wanting to get his or her hands dirty with a fun welding job. You will need a few choice tools beyond the norm, most importantly a good MIG welder. We used a Miller Electric Millermatic 211 with AutoSet. This unit was designed for beginner and pro alike; its dual-voltage MVP plug allows use on both household 120V power and 230 V. The Millermatic 211 even detects the voltage without any action required on the user’s part. Miller also has the normal controls pros expect, like those for wire speed and amperage, but the novice will appreciate the 211’s ability to adjust power and wire feed settings automatically by just telling it the material thickness and weld wire diameter. An anti-spatter feature also reduces slag and spit on start-up. It’s the perfect mate for your home garage or pro fab shop. Besides a welder, you’ll also need a cutoff wheel, air saw, high-speed grinder, metal snips, dead blow hammer, chisel, air chisel, prybar, spot-weld cutter, and drill (or spot-weld hole punch).
The floorpan overlaps with...
The floorpan overlaps with the firewall pan, and these spot welds need to be drilled out with a spot weld remover and a drill. The remaining overlapping scrap is chiseled out. The idea is to preserve the firewall panel—not cut into it. Before continuing, you’ll need to grind all the rust off where water collected between the spot welds.
With this job out of the way, we believe we’ve finally eradicated the last of the rust from Project Nova. Now we can get on with the business of installing our Auto Meter Elite Series gauges, Dynamat sound deadener, carpet kit, and a custom fabricated package tray from Outlaw Motorsports. We’ll bring that to you in the coming months. Then we tackle the tune-up with a serious session on the chassis dyno. We can almost taste victory, and it’s all due to the multifaceted folks at Outlaw Motorsports!
This handy body shop tool...
This handy body shop tool punches 5/16-inch diameter holes with ease, but you can use a drill to make holes roughly every 2 inches apart. Here, Aschtgen punches the holes where the pan meets the rocker channel.
After all four corners of...
After all four corners of the patch panel have been tack welded in place, and the spot welds at the firewall joint and rocker panel have been completed, the overlapping areas need to be cut to create a clean butt-weld. The process starts with using a cutoff wheel to cut a small slit in the overlapping zone, then cutting it along the seam with an air saw, removing the excess overlap scrap, then alternating between a hammer and welder to mate the surfaces perfectly. You’ll see it here in a bit …
It’s best to remove the entire...
It’s best to remove the entire cancerous section in one piece so it can be laid over the new patch panel, and its outline traced. You’ll need to cut the patch panel oversized, then gradually cut away with snips the extra metal until it fits in the car.
Aschtgen is in the final stages...
Aschtgen is in the final stages of fitting the panel. Note that the only side not trimmed is against the outside rocker channel where the floorpan bends down at a 90-degree angle—the other three sides are shown here to overlap at the driver seat, firewall, and trans tunnel. By the time we’re done, there will only be overlap at the firewall and outside rocker (where the factory spot welds will be reproduced).
You don’t want to go blazing...
You don’t want to go blazing along your weld seam when dealing with thin metal—18 gauge, in this case. To keep the heat from warping your work, make a series of spaced-out tack welds, and work the surrounding area with a hammer periodically to get both halves to match up for the perfect butt-weld.
Here’s the same area after...
Here’s the same area after Aschtgen has butt-welded the length along the driver-seat seam. To give the work a factory profile, you’ll want to grind the welds flat with a high-speed grinder and some 36-grit wheels.
Working along the trans tunnel,...
Working along the trans tunnel, you can get a better idea of how Aschtgen likes to cut away the old floor to prepare for the butt-weld. (“Overlapped welds are for sissies,” Aschtgen says!) Note how he’s following the contours of the new piece. Since the work is firmly held in place by the other welds, a near gapless seam is created.
And let’s not forget about...
And let’s not forget about the constant process of grinding that’s needed to prepare all the weld surfaces. Shortcut the grinding and the quality of the welds will diminish greatly.
With the excess overlap cut...
With the excess overlap cut and trimmed off, the seam at the trans tunnel can be periodically tacked, then followed up with a complete bead along the entire edge. The Millermatic 211’s AutoSet feature will ensure that just the right amount of wire feed and amperage will produce the perfect weld. No Millermatic with AutoSet? As a starting point, you can set your 230V MIG for 30 inches per minute when using .030-inch diameter weld wire on 18-gauge steel (whatever amperage corresponds to 18 gauge on your MIG).
Here Aschtgen uses the hammer...
Here Aschtgen uses the hammer to get the two edges to mate evenly. (Remember that the patch panel originally sat on top of the original metal.) This is an iterative process in which you will alternate welding with hammering to create an even surface.
After all the welds are completed,...
After all the welds are completed, you’ll want to grind down the welds in areas that aren’t spot welded from the factory, then you’ll want to spray the finished work area with a material that will protect it for the long haul. Ordinary spray paint isn’t going to do that. Instead, use Eastwood’s Extreme Chassis Black, which is designed to take the beating over the course of decades. With three times the amount of protecting resins, Extreme Chassis Black will outlast the rest of the car.
Wanna see more? Check out...
Wanna see more? Check out the “Project Nova—Floor Patch Panel Repair” video on YouTube.com/PopularHotRodding.
|What To Get
|Dynacorn floorpan full, LH ’68-74
|Extreme Chassis Black aerosol
|Millermatic 211 Auto-Set MIG