Cubes = Cheap TorqueAcceleration that pins you to the back of your seat is the direct result of the engine's torque output. Torque is a function of the charge weight drawn into the cylinder. The greater the charge weight, the higher the torque and the greater the acceleration. It's that simple. Inducing greater charge weight is achieved by means of a supercharger of some kind, nitrous or more cubic inches. By far, the cheapest route to torque is more cubes via an increase in bore size, especially if it is done at the time of a rebuild.
Big over bores are about the cheapest inches you can get. Stroker cranks-and there are some good inexpensive ones around these days-are great, but be aware they are better yet when paired with big over bores.
The days when bores were almost universally half an inch thick are gone. Weight reductions and economy of material have seen to that. This means before considering a big over bore it is paramount that we know whether or not the block will deal with it. Cylinder walls that get too thin will suffer excessive blow by and eventually fail (and inflict a degree of financial ruin). The sonic tester allows you to determine exactly what you are dealing with in advance. It not only ensures you do not waste time and money machining up a block that is doomed to failure, but also it can reveal some very low-cost performance gems.
The first year of owning the sonic tester, we found two 400 Chevy blocks that were as thick as Bow Tie race blocks. Both of these were bored plus sixty and still had cylinder walls that, other than at the siamesed section, were around the 300 thousandths mark. One of these blocks came from a salvage yard, the other from a swap meet. One of these went on to be a 441-inch small-block, the other with a shorter stroke crank, a 427. These blocks each cost $75 a piece. By comparison, a pair of Bow Tie blocks would have set us back well over $2,000.
Staying with small-block Chevys a little longer, it's generally believed that for a performance 350, any bore over +.030-inch is out for a high-performance application. Because of this belief, there are a lot of unwanted +.030-inch blocks around. The bottom line here is that 2 or 3 blocks out of ten will go to +.060-inch and still leave the cylinder walls at or above the average block selected on the basis of minimal visual core shift. We have picked up a couple of very clean +.030-inch blocks that tested out okay for as little as $20! Bored to .060-over, they gave 5 cubes more and subsequently proved fine for 500-plus horsepower build-ups.
Also in the first year of ownership of a sonic tester we found a 302 block that, at .060-over, was still thicker than 2-out-of-5 standard blocks. Knowing how delicate small-block Ford blocks can be, we made good use of the sonic tester to weed out thin blocks. For a reasonably reliable 500hp small-block Ford, probably half the blocks out there are non-starters.
Another notable find the first year was a 454 big-block Chevy block that had cylinder walls over about 400-thousandths thick. This made a perfect candidate for a .125-overbore using KB hypereutectic pistons and boosting inches to 482. That block cost $60. The money saved by being able to utilize stout production blocks instead of having to buy factory/aftermarket race blocks was about five times the cost of the Sonic Tester-and that was just the first year. Along with that saving was the near certain grief we avoided by detecting blocks totally unsuitable for the rigors of high output.