When you are assembling a motor or new engine components, torquing the bolts and nuts to the manufacturer’s specification is very important. Bolts like the cylinder head bolts or studs require the right amount of torque in the right sequence to ensure maximum engine potential.

So needless to say when you are working on your engine, knowing how to torque fasteners and how to read them is very important.

Before we get into learning how to torque bolts and fasteners, let’s take some time to discuss what the fastener does and what it’s role in the automobile is.

What is a Automotive Fastener?

Automotive fasteners are nuts, bolts, studs and screws used to hold two or more parts together or create a seal. There are a few things to keep in mind when working with fasteners, whether you are rebuilding a motor or bolting on a part. Almost all of them use a locking device of some type, either a lockwasher, locknut, locking tab or thread adhesive.

All threaded fasteners should be clean and straight, with undamaged threads and undamaged corners on the hex head where the wrench fits. Develop the habit of replacing all damaged nuts and bolts with new ones.

Special locknuts with nylon or fiber inserts can only be used once. These kinds of bolts and nuts are most often used in the suspension, so it’s important you are vigilant in replacing the nuts after use. If they are removed, they lose their locking ability and must be replaced with new ones.

How to Remove Rusted Bolts

Bolts and nuts exposed to the elements, like the ones on your exhaust system or catback are most likely rusted. Rusted nuts and bolts should be treated with a penetrating fluid to ease removal and prevent breakage.

We prefer the Blast Away brand, which we use in all of our How-Tos involving exhaust work or suspension work for getting those rusted bolts and nuts loose.

After applying your favorite rust penetrant, let it work for a few minutes before trying to loosen the nut or bolt. If a bolt or stud breaks off in an assembly, it can be drilled and removed with a special tool available for this purpose.

Generic Torque Specifications

If you lack the general information about the torque specifications in your vehicle, we’ve included a generic listing that’s pretty good for most bolts. These values must be known even if you know how to torque fasteners properly.

Metric thread sizes – Torque Values in ft lbs – Nm

• M6 – 6 to 9 ft. lbs – 9 to 12 Nm
• M8 – 14 to 21 ft.lbs – 12 to 28 Nm
• M10 – 28 to 40 ft. lbs – 38 to 54 Nm
• M12 – 50 to 71 ft. lbs – 68 to 96 Nm
• M14 – 80 to 150 ft. lbs – 109 to 154 Nm

Pipe Thread Sizes – Torque Values in ft lbs – Nm

• 1/8th – 5 to 8 ft. lbs – 7 to 10 Nm
• 1/4 – 12 to 18 ft. lbs – 17 to 24 Nm
• 3/8th – 22 to 33 ft. lbs – 30 to 44 Nm
• 1/2 – 25 to 35 ft. lbs – 34 to 47 Nm

US thread sizes – Torque Values in ft lbs – Nm

• 1/4-20 – 6 to 9 ft. lbs – 9 to 12 Nm
• 5/16-18 – 12 to 18 ft. lbs – 17 to 24 Nm
• 5/16-24 – 14 to 20 ft. lbs – 19 to 27 Nm
• 3/8-16 – 22 to 32 ft. lbs – 30 to 43 Nm
• 3/8-24 – 27 to 38 ft. lbs – 37 to 51 Nm
• 7/16-14 – 40 to 55 ft. lbs – 55 to 74 Nm
• 7/16-20 – 40 to 60 ft. lbs – 55 to 81 Nm
• 1/2-13 – 55 to 80 ft. lbs – 75 to 108 Nm

This generic chart above is a good rule of thumb on knowing How to Torque Fasteners, but you should always follow the manufacturers specification for the bolt in question. Tightening the bolt to the exact torque specification is very important in your vehicle, so make sure you have the right value before proceeding.

Most threaded fasteners should be tightened to a specific torque value (torque is the force applied to a threaded component). Overtightening the fastener can weaken it and cause it to break, while undertightening can cause it to eventually come loose.

Fasteners laid out in a pattern must be tightened in the manufacturer specific sequence. Items like cylinder head bolts, oil pan bolts, differential cover bolts, and more must be loosened or tightened in sequence to avoid warping the component.

Have any questions about our How to Torque Fasteners Guide, stay tuned for more Nuts and Bolts articles to come.