A magnetic particle inspection station (a wet bench) has a large-diameter magnet that creates a magnetic field. The component being checked passes through this field.
Once the component has been lightly magnetized, a dye fluid is applied and inspection is done using a UV light (or black light). These machines usually have a curtain surrounding the testing area for better UV viewing. Here Bob Fall, of Fall Automotive Machine in Toledo, Ohio, prepares to inspect a crankshaft. The curtain is left open only for the sake of this photo.
This photochemical inspection process is used with or without the need for ultraviolet light. It can be used to test ferrous (steel/iron) and non-ferrous (aluminum and titanium) materials. Dye penetrant testing uses special chemistry to reveal surface cracks. Because no magnetic field is involved, this process can be used on any steel, cast-iron, aluminum, or plastic part.
The process typically involves three chemicals: a cleaner, a dye, and a developer, but it also often uses a cleaning solvent to remove any grease. Spraying the special cleaner prepares the surface. A dye penetrant is then sprayed onto the part. This dye seeps into any cracks, pits, or other surface irregularities.
A dye penetrant kit. This is Goodson’s Glo-Kit, complete with cleaner, penetrant, developer, a supply of rags, and an ultraviolet light.
Once the dye is given a few minutes to soak and dry, a special developer is then sprayed onto the part. The developer reacts with any concentrations of the dye, such as in a crack line. A readily visible, colored line reveals the crack. There are two types of these kits: One allows cracks to be seen under ambient room lighting; the other provides really bright-colored crack visibility under ultraviolet light. Once the crack is located and marked, a cleaning solvent is used to wash off the dye and developer.
Dye penetrant kits are available in affordable spray-can kit form from a number of sources, such as Goodson Tools. Additional spray cans are available individually when replacement is needed. Magnaflux Corporation also offers a similar Zyglo dye penetrant kit in a variety of sizes. It has a florescent dye that’s viewed under UV light (some kits include the black light).
For example, the procedure for using Goodson’s Glo Kit is simple. Clean the surface using a fast-drying solvent or hot water and soap. Rinse and dry. Spray the Goodson Cleaner onto the surface. This is a fast-drying solvent that prepares the surface. Allow this to completely dry. Then spray a liberal amount of penetrant. Allow this to soak for about 5 minutes. Using a clean rag, wipe off any excess. Next, spray several light coats of developer onto the area until you see a white chalky appearance. Place the UV light over the surface and inspect for cracks, which are revealed as contrasting lines.
The three-chemical process involves a cleaner/solvent that prepares the surface, a penetrant that seeps into any cracks, and a developer that allows the black light to highlight any cracks.
Spray the cleaner onto the area and allow it to dry completely.
Spray a liberal amount of penetrant to the inspection area, and allow it to dry for about five minutes.
After wiping off any excess penetrant, spray several very light coats of developer until the area starts to look chalky-white.
Using the black light, inspect for cracks.
The head is immersed in a water tank, with compressed air pumped into an exterior water passage. A rubber fitting creates a seal for the passage that allows the compressed-air connection. Any leaks are evident as bubbles.
A dye penetrant check found this crack leading from a spark plug hole.
Any of these kits are easy to use and come in handy for a variety of crack-checking jobs, including not only engine parts (blocks, cranks, rods, intake and exhaust manifolds, heads, etc.). They also work on socket wrenches, race car suspension parts, welded brackets, brake rotors, car frames, etc.
Pressure testing is indispensable for inspecting a cylinder head or other engine components for cracks, pinholes, porosity, or erosion. Two types of pressure testers are available. A positive pressure tester involves sealing all passages with special plugs. A gasketed sealing plate is mounted to the head deck. The head is then secured to a handling fixture and immersed in a water bath. Compressed air is introduced into the head revealing any leaks (cracks, faults, etc.) as bubbles escaping from the head.
A negative pressure tester (vacuum) can be used to check valve seating. With valves closed, special plugs are installed into the ports and vacuum is applied. Any drop in vacuum pressure confirms that a specific valve(s) is not sealed against its seat.
A bench vacuum tester allows testing for valve seating by applying vacuum to a spark plug port. Any drop in vacuum pressure indicates a poor seat seal.
To blueprint an engine block, you must accurize it. You must achieve the proper bore dimensions, but also must consider the total geometric state of the block and correct any deviations from ideal geometry. This means that you inspect and machine in