The reference to our hot rods as toys implies that we are somehow childlike and compelled to continue to play with toys. While I personally feel vintage cars and hot rods are much more than simple playthings, I must admit that on occasion I do still play with blocks. These blocks come in all sizes, sometimes it’s big-blocks, small-blocks or, in this case, lowering blocks.
It all began during the suspension build of my 1960 Corvette, but the same principles apply to any parallel leaf spring rear suspension. I originally used 2-inch lowering blocks to drop the car proportional to the amount of lowering provided by the new Martz IFS up front. This seemed about right as the goal with this car was to have a pleasantly lowered car versus a more modern, “slammed” ride height. The front suspension utilized 2-inch dropped spindles to achieve the desired lower stance. The problem arose when the 2-inch lowering blocks in the rear too closely matched the dropped spindles up front, resulting in a nearly level car. I believe real hot rods need a rake, not a level stance. So it was time to either lower the front a bit or raise the rear just a little. We could not lower the front any more without having an undesirable control arm angle so we turned our attention to the rear of the car.
The solution was simple enough, put a shorter lowering block between the axlehousing and the leaf spring to effectively raise the car. We began the process by measuring the height from the ground to the center of each rear wheelwell. During this process we discovered the right side of the car was 0.25-inch lower than the left (driver) side. That is not a huge discrepancy but a level car is still the target. So we decided to build our own lowering blocks, with one block being 0.25-inch taller than the other to level the car. The larger block will go on the high side of the car. While we decided to fabricate our own lowering blocks it should be noted that lowering blocks are available from many sources, such as Speedway Motors, ranging from 0.25 inch to several inches. Our decision to build our own blocks comes from the fact that we enjoy doing such things. It was that simple, and, oh yeah, I’m cheap.
While our fabricated lowering blocks were used to achieve the desired front-to-rear and side-to-side stance, lowering blocks could also be used for corner balancing or squaring the rear axlehousing in the frame. As a matter of fact, adjustable lowering blocks are available to dial in alignment. Likewise, if a slight side-to-side alignment of the rear axlehousing is required, that can be achieved by fabricating slightly offset pins on the lowering blocks. So, as you can see, the basic lowering block can be reimagined to perform several important changes to a parallel leaf rear suspension.
The blocks we fabricated were dual purpose: to lower and level the car. It required an afternoon of fabrication and a couple hours of disassembling and reassembling the rear suspension before we achieved both goals. The fabrication process is simple enough, requiring only basic fabrication and welding skills. As always, measure twice, cut once and take your time for the best results. Follow along with our photos and you just might decide it’s time for you to play with blocks again.
1. Building custom lowering blocks can help you achieve the perfect ride height on your parallel leaf spring suspension.
2. The basic block is formed from 1x2-inch box tubing. Our finished blocks will measure 1 1/2 inches on the driver side and 1 1/4 inches on the passenger side to level the car.
3. We made our lowering blocks 1/4-inch longer than the pad on our Currie rear. This ensures full weight bearing on the block.
4. The tubing is easily cut with our port-a-band saw. A hand hacksaw or cutoff wheel will perform the same function.
5. We also cut three pieces of 1/4x2-inch flat stock steel. We will add these pieces to the box tubing to arrive at our desired final block height.
6. For the 1 1/2-inch block we stacked one piece of the 1/4-inch material on the top and one on the bottom of the block. Carefully align the pieces and hold them in place with a C-clamp.
7. We tack welded each piece in three places on each side and then removed the clamp. We used our Miller Synchrowave 200 TIG welder to join the pieces. Strong, clean welds are the result.
8. By making the other block 1 1/4-inch tall we are able to compensate for the 1/4-inch variation in ride height between the driver and passenger side of the car. This block required only one piece of the 1/4-inch flat stock.
9. Here we can see the two blocks side by side. The taller the block, the lower the car. The next step was welding a piece of 1/4x2-inch flat stock on each end of the box tubing. This will provide strength and prevent dirt from gathering inside the lowering blocks.
10. Now that the ends are closed on the blocks it is time to drill the center hole in the block with a 1/2-inch drill bit. Carefully measure and mark the hole.
11. After drilling a smaller pilot hole we drilled the final 1/2-inch hole. It is important to drill the hole perfectly square to the face of the lowering block.
12. On the top of the lowering block we welded a short piece of 1/2-inch bar stock. We beveled the hole before welding so our TIG weld would be very tight to the bar stock and flush with the block. It is important that the entire face of the lowering block contacts the spring perch on the rear axle.
13. The pin we welded in the top of the lowering block locates the block into the rear axle spring pad, while the hole in the bottom of the block is for the spring bolt on top of the leaf spring.
14. And here we have the two finished blocks, the only thing left to do is a coat of primer followed by a couple of coats of semi-flat black paint.
15. The new lowering blocks did exactly what we had hoped. The car now has a nice rake and is level from side-to-side. Not bad for an afternoon of fabrication. The aluminum wedges are there to correct the driveshaft angle, but that’s another story for another day.
Photography by the Author