Cowl Swap - Repairing An Abused Flatfender TubPosted in How To: Body Chassis on June 30, 2014 0) (
Our pal Mike literally drug this flatfender off a pile of scrap steel at a junkyard. It was in line and hours away from its final fate: to meet “the claw” and be pressed into a square of steel along with old tricycles, poop-pipe, and a toaster oven or two before being shipped off to be melted down. It was 1995, and Mike, being a lifelong Jeep freak, saw the Jeep, knew its fate, and talked the steel recycler into selling him what was left of the Jeep rather than crushing it. This score included a fairly straight tub, fenders, grille, tailgate, frame, axles, windshield frame, and so on. The best part: Mike only paid $150 for the Jeep and saved it from a fiery fate and a future as a soup can or brake rotor. Fast forward nearly 20 years and Mike’s junkyard flattie has been an on and off project that is finally getting dangerously close to being driven on the road and trail once again. Mike has meticulously gone through all the parts on the Jeep making them like new, including having almost the entire floor and hat channels replaced. One major hurdle was the strangely mangled cowl on the tub. It had been dented, cut, heated, and warped to the point that it resembled a wavy piece of bacon more than the original flatfender cowl. Replacement was overdue, and Mike had recently bought a reproduction cowl. We figured we’d lend a hand and help Mike repair the last major part of his junkyard flattie with a cowl swap and shoot pictures of how to complete the job.
Here is the offending cowl. We are not exactly sure how it got so warped and mangled, but it is clear that along the way someone did a not-so-good job of clearancing the firewall and cowl for a Chevy distributor and then did a shoddy repair to the clearance holes. Also, somehow the cowl was heated with a torch or was accidentally set on fire with some kind of accelerant, which caused a fair amount of expansion and shrinking in the metal. Enough to make the cowl look kind of like a wavy piece of bacon.
We started the swap by going around the cowl and marking the center of all spot welds we saw with a permanent marker. We then went back with a punch and punched the center of each of the spot welds we found.
We then used a nifty spot-weld cutter like this one from Summit Racing (PN BRC-13224, $14.97). It’s like a miniature hole saw with a centering pin that is spring loaded. You place the centering pin on the punched center of the spot weld and slowly apply pressure. The teeth of the mini-hole saw then cut around the edge of the spot-weld. Be careful to only cut through the upper layer of sheetmetal and don’t press too hard or run the drill too fast or you’ll burn up or break the teeth off the mini-hole saw.
We also used a cut-off wheel to cut through the factory welds on the sides of the cowl. Cut slowly and be sure you don’t cut too far into the metal below the cowl.
Once all the spot welds have been drilled and the welds on the side of the cowl were cut we could pry the factory cowl panel up and away from the tub. Once the old cowl was off, we went back and ground down what was left of the factory welds and the small circles left from the spot-weld cutter.
Fast forward a few weeks and Mike has been busy wiring the Flattie, added a firewall-mounted heater, and a set of hanging swinging pedals under the cowl. Now’s the time to do this since the dash is not removable, and once the new cowl is on, we would have to do all this work from below the cowl and dash.
Here, Mike uses an angle die grinder to clean the paint off the dash, firewall, and tub where we will be welding. Make sure to get all the paint and rust off the metal, or the welds will have imperfections and porosity.
Next, we dry fit the new cowl several times, tweaking it here and there to ensure the best fit before we started welding. We then drilled what seemed to be like a million 3⁄16-inch holes along the firewall seam and dash lip of the new cowl. We then laid a leather welding apron over the Jeep’s wiring (to protect it during welding) and used clamps, locking pliers, and a large ratchet strap to hold the cowl in place while we rosette welded through the many 3⁄16-inch holes.
The best course of action is to start welding near the center of the dash and work outwards using large clamps to push the cowl down on the dash. Then make your way along both sides, being careful that the rolled edge of the new cowl goes over the sides of the tub. We did plenty of tack welding several inches apart, allowing time for the tacks to cool. This, combined with hammering and more tack welding, got the seams to line up pretty well. Then work along the front seam with the firewall clamping the seam together and filling the rosette welds.
In the end, our job probably isn’t quite ready for a concourse restoration judging as some of our welds are porous, but they really are not that far off from what came from the factory and match the rest of the tub. In hindsight, we probably should have been less meticulous about pressing down on the corners of the cowl on the dash. Because of this, we got the sides of the new cowl a bit too low, and the seam on the side of the tub interferes just a little bit. Clean the rosette welds up with a 4 1⁄2-inch grinder with a flap wheel and prime or paint.