While technology has made life more complicated than ever, it's also arguably better in many regards. So too is the case for engine building, where horsepower per cubic inch (or liter) has far surpassed anything from the peak of the muscle car era. That's not to mention better fuel economy, fewer harmful emissions, and a modern engine's ability to last well over 100,000 miles without any perceptible wear. However, achieving those accomplishments also requires a more stringent machining process.
Once
upon a time, if an engine's bore was sized correctly, well-rounded, and straight, then that was good enough to throw in some pistons. Upon startup, the piston rings would handle any final smoothing tasks and remove tiny aberrations from the cylinder walls during the new car break-in process. That's why, historically, a vehicle's first oil change interval was shorter than usual -- to quickly remove excess metal particles resulting from break-in.
Fast-forward to the present when many engine builders give their cylinders the crosshatch treatment as a final step in machining the engine block. Crosshatching is just what it sounds like, a multitude of scratches cut into the cylinder walls. Think of a number sign (#) turned at an angle and repeated hundreds of times. The choreographed scratches from crosshatching help to retain the proper amount of oil on the cylinder walls for lubrication, while also providing a good surface for the piston rings to seal to for building compression.
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Get Yourself A Dingle Ball
When performing crosshatching, both the depth and angle of the crosshatching are variable and too much or too little of either won't yield good results. Crosshatch angles that are too shallow -- in other words, too horizontal -- allow too much oil to accumulate on the cylinder walls, which could be one reason why your car is burning oil. Shallow crosshatch angles can also prevent the piston rings from rotating in their grooves, a process which sheds heat.
On the other hand, crosshatching that's too steep, or vertical, will permit engine oil to drain down the cylinder walls too quickly, hampering proper lubrication. As one might imagine, too little oil in this critical area will lead to rapid piston ring wear. So what is the proper angle? Car manufacturers and the makers of piston rings alike recommend anywhere from 27 to 45 degrees from horizontal. Proper angle notwithstanding, grooves which are cut too deep or wide will result in both high oil consumption and piston ring wear.
Obviously, owners don't have any say in how automakers machine their vehicles' engine blocks. However, if your vehicle is reaching the point where rebuilding the existing engine or swapping it for a remanufactured unit is in the cards, you or your mechanic can research the rebuilder's crosshatching chops. Also, products exist that allow shadetree mechanics to hone to perfection. One popular model fits in a regular drill chuck and is called the flex-hone, which some gearheads affectionately call dingle balls. That sounds like something dirty, but it's actually a poke at the dozens of silicon carbide globules that comprise the tool.
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