Thread Repair Insert
A coiled wire or solid bushing used to rebuild stripped threads in an engine block or component.
A thread repair insert (often referred to by the brand name Helicoil) is a specialized fastening insert used to restore stripped, damaged, or worn internal threads in metal components, particularly aluminum engine blocks, cylinder heads, and transmission housings. It is typically a precision-formed coil of stainless steel wire or a solid threaded bushing.
The process of using a thread repair insert involves drilling out the damaged threads, tapping the hole with a special oversize tap, and threading the insert into the newly tapped hole. The insert's inner threads match the original bolt size and pitch, restoring the hole to its original specifications while often providing a stronger, more durable thread than the original parent metal.
Thread repair inserts are widely used to repair stripped spark plug holes, exhaust manifold bolts, and cylinder head bolt threads. They prevent the expensive need to replace entire engine blocks or cylinder heads due to a single damaged thread, saving time and repair costs.