Quick Tech: Magnetic Particle Inspecting Engine Components

If you’ve been around engine building for any length of time, you’ve probably heard about components — usually blocks, connecting rods, and cylinder heads — being “Magnafluxed,” “mag checked,” or simply “magged.” You’ll notice that “Magnaflux” is capitalized, because that is a proper noun — it’s a brand name. Much like how “Kleenex,” “Q-Tip,” or “Thermos” have become eponyms to describe the items, rather than just a brand, Magnaflux has done the same for automotive magnetic particle inspection.

If you’ve ever spent time in any metal fabrication or manufacturing arenas, you’re probably familiar with the magnetic particle inspection process. If not, we’ll explain. Magnetic particle inspection is a form of non-destructive testing designed to highlight any structural flaws in a ferrous (containing iron) material.

By magnetizing the surface to be inspected and then adding a magnetic particle powder (either wet or dry), any surface imperfections will disrupt the magnetic field, which allows the powder to settle into them. Once the excess powder is removed, the previously invisible (or barely visible) imperfections stand out as bold streaks of color (based on the color of the powder used).

Diving specifically into automotive applications, there are a few things to realize. The first is the process only works on iron blocks, iron heads, and steel rods. Since aluminum isn’t ferrous, it’s not magnetic, and the process doesn’t work. Magnetizing the parts to be inspected might conjure up images of a science experiment with a Tesla coil arcing in the background, but it’s actually a rather mundane process, as you can see in the video here.

Here, Beck Racing Engines inspects our Gen-IV LY2 4.8L engine block prior to undertaking the machine work we have slated for it. Luckily everything checked out good, and we are clear to proceed knowing we have a solid foundation on our hands.

A handheld electromagnet, usually with articulating arms (depending on the brand and model of equipment used) is placed across the area to be inspected. The magnetic powder is then sprinkled onto the magnetized surface and then gently removed, much like dusting for fingerprints. Since the powder will settle into any imperfections, they become visible.

Generally, because of size limitations, the process can take a bit of time, as every area of concern has to be individually checked. Not only that, but the magnet should be rotated into two positions when checking, as a defect that runs perfectly parallel between the magnetic poles might escape detection. The best-case scenario is that no powder sticks at all and your item is in perfect working order. However, an imperfection showing up isn’t necessarily the end of the world, as oftentimes it can be repaired. Whether it’s worth the time and effort of repairing is another story altogether, however.

This is how a crack would appear, if there were one. With the magnetic field interrupted, the powder settles right into the crack, highlighting it. One thing to note is that you need to check each spot in two directions, as any cracks that run perfectly parallel to the electromagnet’s poles might not show up.

While not strictly a necessary step when building or rebuilding with used parts, in the case of an engine block or cylinder head, it can prevent you from pouring a significant amount of time, labor, and/or money into a bad casting, as was the concern with our core engine for the LS5.0 project. After a solid cleaning, Frank Beck at Beck Racing Engines thoroughly checked the block with his Magnaflux equipment, and the block passed with flying colors. Now, we have no concerns whatsoever about moving forward with the necessary machine work to get our Gen-IV 4.8L block into fighting shape.

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About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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