What Can You Use for a Minor Crack in an Aluminum Block?

Pinning

• Pinning or stitching is used when the cracked part does not require replacement but still needs extensive repair. Small holes are drilled along the sides of the crack. The holes are then lined with a thread sealant, and a small pin is screwed into the opening. Other pins are placed in a stitching pattern along the crack. This creates a danger that you may weaken the block further with the holes, but it can also provide structural support when done correctly.

Brackets

• An alternative form of stitching uses brackets that are pinned down across the crack itself. While brackets and pins are the two main forms of stitching, a number of different fasteners and plugs may also be used. More advanced versions are locks that can fit into a metal block through pre-cut holes, bolted in to lock the crack in place and prevent expansion.

Welding

• For iron blocks, furnace and flame welding may repair the crack, but aluminum is a more delicate alloy and will not respond well to these techniques. Instead, a welding gun may be used to repair minor cracks by melting a line of new metal along the crack surface and binding it together. TIG welding, which uses a constant gas flux to protect the weld, is the preferred method, but some preheating is also recommended to prevent the aluminum from cracking under the heat.

Putties

• Putties may be used along with cleaning and buffing to restore a smooth surface in the case of minor cracks. There are epoxies and metal-fill putties with metallic elements that can fill cracks and prevent some issues. These putties are generally not recommended for aluminum heads in engines or other complex systems.