When your head gasket fails, your engine could start to overheat and reach dangerously high temperatures. Exposure to sustained high temperatures can weaken the threads inside your block. When you go to torque down the new head bolts after replacing the gasket, you may accidentally pull the weakened threads right out of the hole. If this happens, you have to decide how to handle the situation to return your vehicle to running condition. Here are the three main options you will have in addressing stripped threads in your engine block.
Fill and Drill
In the past, it was common to remake the damaged bolt holes using new materials. For this process, the bolt hole would be filled with liquid metal that was then allowed to solidify over the course of several hours. Afterward, you would drill out a brand new hole and tap it for the bolt size you need to use for your engine application. It is less common nowadays because this process is fairly complex, so many people choose to quickly install thread inserts or simply replace the block instead.
A thread insert instantly restores the functionality of the previously destroyed bolt hole. To perform the thread insert repair process, you must use purpose built tools to drill the hole bigger, tap new threads and install the metal insert. Once you complete this process, you can torque down the bolts like normal. You may notice that the threads feel even more solid than stock with the insert installed.
If you do not have the tools on hand to perform the insert installation or to fill and drill the damaged bolt hole, you can actually just replace the entire bottom end of your engine. You can find a replacement engine block from the local junkyard or by looking through the classified ads for a donor car. You should have the engine looked at by a machine shop to verify that the deck surface is true before performing the install. You can also choose to rebuild the bottom end of your engine to renew its internals and prevent future part failures.
Making Your Decision
After weighing your options, you can choose one of the three fixes listed above to fix your engine. If you are uncomfortable performing the thread repairs or engine replacement process yourself, you can take your vehicle to a shop like Trac Engine Services Ltd to have the work performed by a professional. Auto technicians have the right tools and know-how to make quick work of this process.