The Right Tool for Threading or Cleaning a Tapped or Threaded Hole

Today we’re going to discuss threading and cleaning a tapped or threaded hole, which is a subject that can get a lot of engine builders in trouble. You might be asking yourself, what are the correct tools for this?

Fortunately, we have Team Summit NHRA Funny Car driver Tim Wilkerson and Frankie Forman from Engine Power to help guide you in the right direction and select the proper tool for the project.

Why Clean the Threads?

You want to minimize and reduce particles in the holes to avoid causing damage to the threads or holes on the bolt. Having debris in the hole might also interfere with torque values as you overcome the extra resistance of the grime in the threads.

You’ll also want to make sure that threads are in good condition and clear to ensure you don’t strip out any of the bolt holes or cross-thread. You’ll also want to make sure you’ve achieved the proper torque valves when assembling and tightening the engine components together. This will ensure even clamping force.

Options for Addressing Stripped Threads in the Engine Block

When your head gasket fails, it could force debris into the threads. When you torque down the new head bolts after replacing the gasket, you could accidentally pull the weakened threads out of the hole. If this occurs, you must decide how to handle the situation.

Thread Insert

A thread insert will restore the functionality of the previously destroyed bolt hole. In order to perform the thread insert process, you need purpose-built tools to drill the hole bigger, tap new threads, and install the metal insert. Once you finish this process, you’ll be able to torque down the bolts like normal. However, you might notice that the threads are more solid than stock when the new insert is installed.

Thread Chasing

This is one subject that can’t be stressed enough. One of the most crucial steps in building your engine is chasing each thread. Part of the fun when it comes to engine building is to ensure that all your threaded holes in the block are in good shape and equipped to handle the torque loads for fasteners like main cap and head bolts.

Although you might not give much thought to the quality of the threads, it’s a challenge when the threads pull out when you’re torquing the last head bolt. Thread chasers are designed to clean dirt and junk from the threads and remove as little material as possible. They also reshape deformed threads to some extent without removing material so you can continue using the original threads.

Restoration kits eliminate a frustrating problem for DIY mechanics – damaged or stripped bolt threads. Clean and straight threads ensure easy bolt removal and allow you to properly apply a fastening torque, which is a must-have for engine assembly.

Machine Tap

Taps are designed to cut new threads rather than chase existing ones. Each time you use a tap to repair a damaged or deformed female threads, the tap will remove more of the existing threads. It reduces the overlap of the female threads in the engine block to the male threads on the bolt. The reduction in overlap often leads to stripped threads.