Knowing the Bolt Tightening Torque Specs for your Car

January 27, 2012

The bolt tightening torque specs are important information to increase performance or perform repairs. A bolt that has been tightened too much or not enough can cause problems and the engine will not run efficiently. If the tightening is very different from the specs then this can even cause significant damage to the vehicle. Additionally, there are different specs depending on whether the bolt is dry or oiled. Each brand of bolt and the type of part it is going into will determine the torque specifications. The quality of the bolt also affects the amount of torque that can be applied. If a higher torque needs to be used, then normally a higher grade bolt is necessary.

Torque Units

Two different types of torque units are used for measuring torque. There are the metric bolt tightening torque units of Newton meters and the US version that uses foot-lbs. These units can be interchanged and converted and a good torque tool will show both units, as some bolts will only show the specs in a specific unit.

Issues with the Car

About a fourth of all car problems actually occur because the fasteners and bolts were loose, even with brand new cars. A bolt that is not tightened properly can lead to an entire section of the engine failing. If the bolt torque is too tight then the bolt can fail and even completely cleave in two.  It is important to check the torque after assembly and then after use as the bolts' torque can change. This is particularly true of car engines where the temperature can fluctuate. By having the torque specs it is possible to check the torque and make corrections so the vehicle is always working at peak performance.

Finding the Specs

If all of the bolts in the car originally came with the vehicle then the torque specs should be present in the manual. However, many car owners will upgrade or add aftermarket parts and these will have their own different torque specs. The type of threading on the bolt, the material of the bolt and any lubrication used will all change the torque specifications. Manufacturers will provide the correct bolt specifications for their products. If you have lost this information, many torque specs can be found online or by contacting the car manufacturer.

Applying Torque

Besides getting the torque specs correct, the order in which bolts tighten is also extremely important. It is quite rare to simply be able to go down a line of bolts and tighten them in order. In most cases a pattern will need to be followed. Specific parts of the engine such as the intake manifold will have a very specific pattern that needs to be followed. If this pattern is not followed then the manifold will crack.

The Best Measurement

If possible, using a torque angle can be a more accurate way of tightening bolts. A regular torque wrench does not manage to get rid of error that is due to friction. By using a torque angle, the torque force that is achieved is much more accurate. This is a very simple tool to use and can make all the difference when tightening bolts in the engine.