How much work you need to put into these problems will depend on the nature of the damage itself and sometimes major replacements will be inevitable, but not in all cases. In the specific case of stripped threaded bolt holes in engine blocks, the problem often has a very specific cause.
However, repairs are usually completely possible and not too difficult to do, just as long as they’re done with mechanically sound repair options kept in mind. This is what we’re now going to cover.
A Rundown of the Hard and Soft in Engine Thread Damage
Decades ago, engines and many other industrially cast manufactured parts were more often than not incredibly hard creations of hardened steel alloys. At one point in time, the use of these metals extended to many parts of a car, including engine blocks, heads, manifolds, housings, brackets and even automotive frames. This applied particularly to bolt holes in steel and iron parts, which would conserve their thread integrity quite firmly despite heavy use.
Over time, hard steel and cast iron were increasingly replaced by aluminum alloys whose hardness ratings were well below those of previous steel parts. Thus, whereas iron and steel parts with Brinell Hardness (HB) ratings of 150 to 300 could be seen in one part of a car, aluminum parts with HB ratings of between 20 and 150 started to become more common. In the case of engine blocks, aluminum alloys with a hardness rating of 150 can be found, but sometimes they’re lower.
Bolts on the other hand often remain much harder, in the 150+range. As a result, where the aluminum alloy of the engine block has a hardness rating that closely matches that of its steel bolts, internal threads often hold firm for much longer. However when steel bolts with 150+ hardness ratings are matched with engine blocks of lesser hardness, thread stripping is suddenly a major, common risk.
Replacing Soft Threads with Hard Threads
Because so many of today’s engine blocks come manufactured with softer aluminum alloy materials, thread stripping has in some cases become more common than ever. What’s more, even though many manufacturers pre-install hardened threading in certain high-stress parts of an engine, the vast majority of threaded holes in an aluminum alloy engine block will come right out of the factory without reinforced bolt hole threading.
This will at some point often cause you to have an engine block stripping problem. The easiest way to fix it is by adding your own hard threads right off the bat.
Hardened Metal Thread Inserts
By simply drilling into your engine block holes with a mechanical drilling tool that slightly expands their width, you can then follow up by adding in hardened steel thread inserts of your own that completely lock into place and reinforced the original hole with a new layer of steel that matches or exceeds what bolts offer.
By doing this, you ensure that your engine block threads get an entirely new lifespan with far harder internal protection. The threads will even feel much more solid than the original threaded hole, especially if its original threading had already started to strip.
The metal thread insert process of repairing engine blocks can also be used as a preventative measure, which is what makes it so great. Thus, instead of using your engine block until its factory-made threads finally fail and possibly cause far worse damage, you can pre-drill them to wider diameters, add in hardened carbon steel threads of your own and firmly have them ready for years of use that forestall deeper damage.
Avoiding Engine Replacement
In the very worst cases, if your engine block has already gone through a process of thread stripping, then thread hardening might not be enough. It usually is, and even a majority of badly stripped engine block bolt holes are remarkably repairable with the right kinds of steel threaded inserts for metal. However, in situations where stripped threads have loosened the integrity of the entire head gasket and other parts attached to an engine block, stress deformities and cracks can form. If these occur, the entire replacement of your engine block suddenly becomes a necessity.
For reasons of repair effort, time and sheer cost, thread-reinforcing your engine block is something you’ll definitely want to do instead of waiting for its bolt threads to cause a catastrophic failure. Carbon steel thread inserts for engines are extremely hard, built to last and provide tremendous, long-term reinforcement.