Remember how I said last month that I'd started a Modified project, but that it would see intermittent coverage in the magazine as I had other projects that should take priority? Well, I didn't expect the project to snowball, but it has, so here's the second installment. Not only does Dagel's Street Rods offer a neat X-member for Model A chassis, but they also sell laser-cut boxing plates. While not exactly hard to cut from steel plate yourself, the Dagel's kit takes all the hard work out of the equation, perfectly cut to provide a stepped weld area where the plates meet the top and bottom chassis 'rails. The kit comes with detailed instruction sheets too, explaining the installation process.
Before I could fit boxing plates, however, I wanted to Z, or kick up, the rear of the frame. You'll remember last month we installed a '40 Ford split front wishbone in the rear and mounted their forward ends to brackets below the chassis. I wanted to Z the frame so the 'bones mounted through the chassis 'rails for a cleaner look, as well as lowering the car. So this is a double feature covering Z'ing and boxing ... oh and a little chassis repair, too!
If you're planning a similar job and will use an original chassis, source the best you can, and ensure it's totally level before beginning work. While mine was rust free and in pretty nice condition, the tops and bottoms of the 'rails had some waves in them that required tweaking, while the left front 'rail was kinked and needed a little heavier repair.
If you're going to tackle...
If you're going to tackle chassis building or modifications, you'll need a jig or table of some kind, as the heat generated during the welding will cause the frame to twist and warp unless it's clamped to something solid. The jig needs to be of heavier-gauge steel than the frame it's supporting, otherwise the jig will warp along with the chassis. I use this dolly for moving and painting bodyshells and it's ideal for our purposes here while tack-welding the frame, though either something more substantial will be needed for final welding or I shall attach the dolly to something heavy like the chassis dyno ramps in the background! Before any work could commence, the chassis was measured to ensure it was square, level, and central on the jig.
I needed to cut a number of...
I needed to cut a number of temporary crossmembers to stop the chassis 'rails moving once the center crossmember was removed, and my trusty Harbor Freight chopsaw proved ideal.
With the chassis level and...
With the chassis level and square, and the temporary crossmembers in place, I cut these brackets from 2-inch angle and welded the chassis to the jig. It ain't moving now!
This is a pretty nice Model...
This is a pretty nice Model A chassis, but it had a few dings and kinks such as this. Before the chassis could be boxed these all required straightening.
Rather than attack the 'rails...
Rather than attack the 'rails with a large hammer, they can be tweaked back into shape using a crescent wrench, adjusted to the thickness of the steel.
The original crossmember had...
The original crossmember had to come out to box the chassis, but more importantly, it wouldn't work with the drivetrain we're planning and will interfere with the crossmember kit. It's riveted in place, so first the rivet heads were ground down.
Once the rivet heads had been...
Once the rivet heads had been ground flush with the chassis 'rail, they were driven out using a punch. It took a few hard whacks to move 'em, as they had been in there for 70 years.
With all the rivets removed...
With all the rivets removed (eight per side) the crossmember was knocked out. Though the chassis is welded to the jig, the temporary crossmembers stopped the tops of the 'rails from leaning in, as the chassis is only welded at the bottom.
Before the chassis could be...
Before the chassis could be boxed, all the holes in the 'rails were plug welded. I cleaned the inner surface of each one using either a die grinder or a file, depending on the size of the hole. If you want to weld caged nuts under the body mounting holes, this is the time to do it, as once the boxing plates are installed there'll be no access. I elected to leave the body mounting holes open for now, as I don't know where my body mounts will be, but welded every other hole closed.
While it's relatively easy...
While it's relatively easy to weld the smaller holes up to 3/8-inch diameter, with no filler material, some of the larger ones are easier to fill by welding a steel plug of similar gauge to the 'rail in place.
Alternatively, larger holes...
Alternatively, larger holes can be filled without a plug by holding a piece of copper behind and plug welding it. The weld won't stick to copper, so it can be removed after welding. Without a thick piece of copper plate handy, I used a pipe bung from the local hardware store held in place with a hammer. Hey, whatever works!
Before removing the wishbone...
Before removing the wishbone mounts I marked their centerline on the 'rails and transferred this to the jig. When the chassis is Z'd these will move rearward a few inches and I needed a reference mark to relocate them.