If you plan to build a high-performance engine so that you can compete on some local events or simply enjoy your weekend drive that much more, then you know that you need to choose the highest quality accessories. Each part of this new engine will come under tremendous strain in its effort to provide you with that output, but some parts will be under more duress than others. Why is it crucial for you to choose the best quality head bolts that you can find for this build?
As you may know, the head bolts connect the cylinder head to the engine block itself and there may be four or six of them on your new engine. These bolts surround the cylinder bores where all the action takes place, and it's important to take into account the sheer amount of pressure that is generated during each revolution. As each piston moves up and down, a high-level of pressure is exerted against the cylinder head and the head bolts have to maintain their rigidity at all times.
This is why it's very important to choose head bolts that have been designed for the purpose and that will be capable of maintaining the right clamping force under high-performance. They must not only be well designed, but they must be kept in perfect condition and installed properly to make sure that they are never overloaded.
Each head bolt may have a specific design and appear to be a rigid fastener, but that's not actually the case. Each of these bolts is designed to stretch to a certain extent, so that it will be able to maintain the same amount of force against the surface, no matter what may be going on within the engine itself.
Remember, a carefully engineered gasket sits in between the block and the cylinder head and this device is meant to segregate lubricant and coolant as well. The gasket is made from materials that are designed with a certain amount of "give" and, as a consequence, an amount of movement is to be expected when the engine is in motion. This is why it is crucial for the head bolts to stretch and contract and the best product on the market is designed to do this without degradation.
When the engine gets particularly hot as it is working under maximum load, there will also be a certain amount of thermal expansion. This will serve to stretch the head bolts even more and especially if the cylinder head is made from aluminium. When the bolts are made, they are designed to stretch to a predetermined amount, known as the "yield point," and no more. This is crucial as if the bolt were to stretch even further than that point it could deform and fail at a later stage.
Always make sure that you buy premium quality head bolts, like ARP head bolts, and never settle for anything less, due to the amount of pressure within and the expected temperature under maximum load.