Model A frames flex. They were designed that way partly because roads weren't all that smooth--or even paved for that matter--in the '20s, and the somewhat limited travel of buggy-sprung solid axles relied on this torsional flexibility to keep all four wheels on the ground.
While today's roads are much more forgiving on a '28-'31 frame, the addition of a heavy V-8 engine and the power it produces aren't. These days, finding bent, twisted, or cracked original 'rails is more the norm rather than the exception, since they're the obvious results of excessive flex. That's why you see so many boxed Model A frame- rails. Although boxed 'rails go a long way toward stiffening and strengthening a frame, an X-member takes it further.
Check out the Super X crossmember kit from Dagel's Street Rods. It's a complete weld-it-yourself crossmember kit designed specifically for the Model A frame. It's already set up to accept a modern master cylinder and includes a GM-specific, but easily modified, bolt-on transmission mount.
Before you start this project, it is important to ensure that your frame is straight, flat, and square. Set the bare 'rails on identical sawhorses on a flat, level surface and warm up the measuring tape. Start at the front crossmember using the center spring-pin hole as your zero point. Measure the distance to the left and right cowl bolt holes and to the rear crossmember where it meets the 'rails. It's not so important what the measurement is, but that the measurements are within 1/8 inch of each other. While you're at it, stretch a piece of string down the center of the frame between the crossmembers from the center spring-pin holes and measure the distance from the 'rails to the string. Again, they need only be within 1/8 inch of each other. If they're looking good, you're ready to get started. If not, Gary Dagel suggests finding a better pair to form the foundation of your pride and joy. Dagel also strongly recommends boxing your 'rails before installing the Super X kit, as it was designed with boxed 'rails in mind. Dagel's Street Rods also offers a complete boxing kit for Model A 'rails so you could do the whole shebang with one order.
