An allen wrench is used to...
An allen wrench is used to unscrew the striker, which anchors into a thick captive plate behind the jamb. The strikers on some cars can get pretty tight, and require a good dousing with penetrating oil from behind, and some time, before they can be extracted.
Work on enough A-Bodies, and sooner or later you'll run across a broken doorjamb at the striker pin. Why is it that this problem seems to crop up in A-Bodies more than on other Mopars? The way the striker pin is attached is different than it is on later B- and E-Body cars. In both cases, the hole in the jamb is backed up by a floating captive plate that the striker pin screws into. The difference is that later B- and all E-Bodies have a serious chunk of metal that the plate is attached to, while on As, the floating plate is simply hung on the jamb's thin sheetmetal. One thing is for sure, there's only two types of A-Bodies, those with broken strikers and those that are going to break.
When I purchased my '70 Dart 340 project car, sure enough, the striker was busted. On this car, the pin was already solidly (and roughly) arc welded to the jamb and backing plate, defeating the stock provision for adjustability. This was the car that got me hip to the problem. Cruising the salvage yards for A-Body pieces, I began noticing the same condition-door jambs either cracked or shored-up with hacked repairs. At least my clean daily-driver '69 Dart's jamb was intact. Purchased several years back as a low-mileage original, this thing was as solid as they get. Driving down the freeway a few months back I heard an uncharacteristic rattling vibration over my shoulder, either from the door or quarter. A quick open and shut of the door, and it was still there.
Closer inspection revealed that the once-solid striker was now wobbly. Blighted. Thirty years of catching the door worked the metal under the striker pin's large washer to fatigue. Finally it broke loose like a coat hanger bent back and forth. At this point there was nothing to do but pull out the tools and fix it. A broken doorjamb isn't a cosmetic ding that can be puttied and painted, it's structural. Think about it. If even the factory metal eventually gave up, anything but a top-rate repair hasn't a chance of surviving. There are ways to reinforce the mechanics of it, adding an extra layer of sheetmetal, or a larger diameter washer under the striker pin-but none of these mods look stock. Rather than re-engineer it, we repaired it back to original condition, and hoped it lasts another 30 years.
We've seen worse, much worse,...
We've seen worse, much worse, but the driver's-side striker in this '69 Dart is wobbly. A few small cracks at the lower left are beginning to come out from under the striker, but the major failure is all the way around the striker's washer.
Strip the paint in the repair...
Strip the paint in the repair area. A 3M Clean & Strip wheel in a drill or die grinder is one of the best tools for the job, quickly removing paint without thinning the metal like a grinder would.
Here's the culprit: The sheetmetal...
Here's the culprit: The sheetmetal skin of the jamb fatigued over the years, and cleanly broke loose behind the striker's washer. Now the striker is only attached to the backing plate (visible through the hole here), which isn't solidly secured to anything. In time the backing plate will pull through the jamb, creating long cracks in the process. The broken piece is marked from behind to show which side goes up, so it can be replaced in the same position.
The broken piece is also stripped,...
The broken piece is also stripped, and ground slightly all around its edge so it fits the hole without hanging up around its circumference. It's vital for a good repair that the pieces sit perfectly flush. The broken piece was slipped back into place and clamped to the backing plate with a long 7/16-inch bolt (440 headbolt) with a nut and washer. Since the backing plate floats, the long bolt allows a handle for getting perfect alignment of the broken piece while tack welding.
Before welding, always disconnect...
Before welding, always disconnect the car's battery.
A MIG welder is used to tack...
A MIG welder is used to tack the broken section while using the long bolt as a handle to maneuver the sheetmetal edges into exact alignment. If the edges are misaligned even a little bit, the area will be impossible to grind smooth without thinning the already marginally-strong metal. It's also essential that the weld doesn't penetrate to the backing plate behind, or you've got real problems, since a plate welded to the jamb's sheetmetal can't float to let the striker adjust.
This is the repair area after...
This is the repair area after tacking, with the clamping bolt removed. The edges of the metal are in exact alignment. Notice the backing plate dropped to its bottom position once the bolt was removed. Make sure it remains free-floating.
Now the gaps between the tacks...
Now the gaps between the tacks are welded solid.
Here's how it looks after...
Here's how it looks after we give the jamb its final weld. A solid, well penetrated weld with no distortion of the surrounding metal.
The welding beads need to...
The welding beads need to be ground back to level the area out. We like these small sanding discs on a die grinder, which gives control in tight areas. The idea is to cut back the beads, leaving the thickness of the surrounding metal intact. In this application, preserving the metal thickness is vital to strength and a sound, long lasting repair.
After grinding, this was it....
After grinding, this was it. Perfectly flat metal with its original thickness intact, and an invisible weld seam. Some final sanding with a D/A sander preps the area for a dusting of primer and paint.
The area was masked, shot...
The area was masked, shot with a coat of PPG DP-40 epoxy primer, lightly sanded with #600-grit paper, then hit with a of couple coats of PPG Delstar acrylic enamel paint. It looks good as new.
Once the paint cures, the...
Once the paint cures, the striker is screwed back in and adjusted, and it's back on the job.