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1947 Chevy Fleetline Rocker Panel Replacement - Rocker's RehabDon't Let Rust Dominate-Replace And Eliminate! From the August, 2010 issue of Rod & Custom By Rob Fortier
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Without the presence of air and water, you and I would rarely have to deal with rusted metal. Unfortunately, we really can't control one of those elements-oxygen-so even in the driest of climates, at some point there will be moisture in the air in one form or another. The majority of electrochemical deterioration of metal is caused by Mother Nature's two most prominent elements, but rust can also be caused and/or affected by other things, such as salt and acids. But no matter what, how, or why, once the process has begun, it doesn't stop until it's been treated, or there's simply no more metal to consume. Ideally, you not only want to address any rust-effected areas on your car, you also need to stop the corrosion and prevent any further damage. Depending on the severity, this can be something as simple as a chemical treatment-which is what we'd all prefer having to deal with-or it can translate into complete sheetmetal replacement. As the cars we build keep getting older, we're starting to see a lot more cases of having to perform major metal repair-even on vehicles that were restored or rebuilt not too long ago (most due to existing rust not being properly addressed). A good sales pitch should... A good sales pitch should not prevent you from coming to your own conclusions before buying an old car. When I first looked at my '47 Chevy Fleetline, it didn't look like this-at least I couldn't see this much of it, as most all the parts were being stored inside the car (this is "post-purchase"). Fortunately, when the severity of rust dictates panel replacement, more often than not, our great resources are there to help in the form of die-stamped or fabricated replacement sheetmetal. From complete floorpans to doorskins, quarter-panels, and probably one of the most replaced portions of '40-50s cars-rocker panels. When it comes to early Chevys, help is but a phone call or click away. Both Chevs of the 40's and EMS offer volumes of replacement part applications for the '37-54 Chevrolet passenger cars-in OE and "street rod" options. While something as seemingly simple as a floorboard section could be repaired with a piece of appropriate-sized sheetmetal, unless you're just replacing a small flat piece, it takes a lot of work (and the right tools) to recreate what GM did decades ago. Rather than recreating the wheel, save yourself the time and effort-spend a little bit more and get a quality replacement. Just because a car gives a... Just because a car gives a good first impression, don't let a book's cover fool you like it did me. Once I'd separated my body from its chassis, I soon realized that I was in store for a whole lot more than I'd "bargained" for. Safely perched on the AutoTwirler rotisserie, the body revealed the severity of the rust that had previously gone unnoticed. My '47 Chevy Fleetline turned out to become a poster child for sheetmetal replacement. In the beginning, it was assumed we'd just have to replace the passenger side rocker panel and the tail pan section. As things progressed (or should I say digressed?), the list kept getting longer: inner trunk floor, front and rear floorpans, inner wheelwells, inner/outer passenger door bottom, etc. And there will probably be more added to the list before we get any primer sprayed on. But thanks to the above-mentioned companies, we've been able to address all of the situations accordingly. The "we" I've been referring to is more Jimenez Brothers Customs (JBC) than me. From the onset of finishing my surrendered attempt at replacing the left side rocker to fabricating a complete new subfloor to accommodate the chassis C-notch, they've attacked and conquered each and every area heavily affected by rust-and will continue to do so (regardless of how much they hate me for it) until the Fleetline's ready for paint. For this month, we'll address the issue that started this whole "mess" in the first place: the rocker panel.  The more the Chevy came apart,...  The more the Chevy came apart, the more apparent the rust damage became. Initially, I had planned to replace the left-side rocker myself-until I realized just how involved the process was. The '42-48 Chevys used an intricate bracing support system that interlocks the rockers with the floorpan, and while you could replace just the outer section of the rocker's box section back then, which wouldn't affect the braces, that wasn't an option now.  After throwing in the towel,...  After throwing in the towel, I hauled the Fleetline down to Jimenez Brothers Customs (JBC) to have the metalwork done properly. With the body on the rotisserie, rather than securely anchored to the chassis, the gaps were checked before adding bracing and removing the doors.  The bracing will prevent the...  The bracing will prevent the body from moving around, thus affecting gaps and fitment, during the rocker replacement. This is mainly an issue because the body is being supported by the rotisserie from the cowl/firewall and the rear of the trunk-not in the center, as it would if still mounted on the chassis.  As I'd just mentioned, the...  As I'd just mentioned, the unique manner in which the '40s Chevy bodies were designed and built will dictate to some extent how they're repaired. Before cutting into any section, like I almost did where the jamb overlaps the back of the rocker, do yourself a huge favor and familiarize yourself with how the pieces fit with one another and why.  Whether replacing the rocker...  Whether replacing the rocker panels or floorpans, you'll need to address quite a few factory spot welds. The hard part may end up being the ability to locate all the spot welds, so you'll want to get the top and bottom of the floors and rockers as clean as possible beforehand.  HTP's pneumatic spot weld...  HTP's pneumatic spot weld cutter was used for this part of the job, as it not only made the removal of the joints easier and quicker, it didn't leave the bigger hole that a drill bit would, and thus less to fill later with new weld. When replacing the rockers, leave the bracing attached to the floors; when replacing a floor section, do the opposite.  Along with retaining certain...  Along with retaining certain flanges that connect one panel to another (via spot weld), the factory subfloor bracing also needs to be retained for structural support-and to make sure it mounts back on the frame correctly. Even if you intend to replace any of the outer brace sections, if possible, leave the original ones in place till after you've installed the new rocker.  The replacement rockers are...  The replacement rockers are purposely oversized (though don't let that get you carried away and cut too much of the old one out), so there will be some trimming required.  Once the braces are free from...  Once the braces are free from the rockers (but still attached to floor), the damaged section can finally be cut out and removed. The plasma (HTP's MicroCut 301) was used for most major cutting, but a cutoff tool (like Ingersoll Rand's cordless IQv) will also work, and in many cases will provide a better surface in which to weld on.  With access now to the inner...  With access now to the inner side of the braces, thoroughly clean with an abrasive disc as best you can-this will be the only opportunity to do so. Furthermore, you may also want to consider treating/coating the insides of the braces depending on how rusty they are.  To avoid damaging the underlying...  To avoid damaging the underlying braces, the sill portion of the rocker was cut around the braces, as shown. The remaining sections of the rocker were removed after the panel was out of the way. It's real easy to slice right through a floor brace (which is another reason replacements are available) if you're not careful.  If, for whatever reasons,...  If, for whatever reasons, you end up needing to repair or replace any of the braces, don't worry-you won't have to do any fabricating (unless you want to), as new ones are readily available.  The accurateness of fitting...  The accurateness of fitting the panel is crucial, as its placement will ultimately determine the bottom door gap as well as the alignment of the rocker trim. Reinstalling the door during this process is suggested. Make certain you've got it fitted just right before you even consider dragging the welder out.  Ultimately, a butt-welded...  Ultimately, a butt-welded joint between the rocker and the floor is best, if possible. For any sections that are overlapped, make sure they're seam-sealed thoroughly to prevent moisture from getting trapped inside.  The rocker panel slips beneath...  The rocker panel slips beneath the stepped flanges on the front and rear pillars in the doorjamb and is re-spot welded-that is, if there's any flange left to weld on. In this case, what did remain wasn't sufficient to work with.  To compensate for the lack...  To compensate for the lack of material, a filler piece had to be made in order to, well, fill the gap. This had to be done on both the A- and B-pillars, as well as fabricating some pieces to replace the sections that the new rockers didn't reach.  While Chevs of the 40's has...  While Chevs of the 40's has replacement sill plate mats-including the hard-to-find moldings-don't rely on them to mask rusted-out or even poorly repaired rocker panels! Do it right while you have the chance. We'll continue next month as things move further inside the car and we tend to the floorboard replacement.
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