NUTS ABOUT BOLTS

Bolts, nuts, and washers: They’re what keep your engine, drivetrain, chassis–heck, the entire car–together. Fasteners are the linchpin for a successful build, but how much attention do you really pay to them? Sure, we want our nuts and bolts to look pretty and not rust, but they’re much more than just another pretty face! Failure of a single critical engine or chassis fastener can cost you tens of thousands of bucks due to a destroyed engine, or even an entire car. Yet with proper selection and installation practices you can virtually eliminate fastener failure. Over the next few months, we’re going to take a granular look at today’s fastener technology with the help of Chris Raschke and the Automotive Racing Products (ARP) crew. Unless you’ve been living in a cave the last 20 years, you know that the good folks at ARP have risen to become the dominant force in supplying bulletproof fasteners for just about every hot rod and motorsport application. In this installment, we’ll look at fasteners retained primarily in tension, concentrating on those used to hold your engine together. What are their unique materials and characteristics, how are they made, and how do you properly install them?

A TENSION HEADACHE

In-use loads affect fastener design, performance, and installation practice. Bolts may be loaded in either “tension” or in “shear.” A bolt is said to be loaded in tension when two joints are clamped together and forces are applied predominantly along the longitudinal axis of the bolt. Examples include most engine fasteners, including connecting rods, main bearing caps, cylinder heads, intake manifolds, and conventional oil pumps. A bolt primarily subject to sideways or bending forces that are perpendicular to its axis is said to be loaded in shear. Examples of shear bolts include most