Tech Stuff

Engine studs: Understanding the advantages of using studs vs. bolts, and tips on achieving proper clamping loads

Text and photos by the author.

In far too many cases, the engine builder’s attention focuses only on selection of the proper components for a specific engine build, determining proper clearances, intake and exhaust volume and flow, surface finishes and precision assembly. Threaded fasteners, the vital link that secures everything together, are often taken for granted. Here, we’ll discuss a variety of issues and concerns directly relating to the most important components of any engine — studs and bolts and their handling.

Studs, for engine applications, are available for most popular engines, especially in terms of cylinder head applications. The use of studs, as opposed to bolts, for cylinder head installation provides a more accurate and uniform clamping load pattern throughout the cylinder head.
<p>Studs, for engine applications, are available for most popular engines, especially in terms of cylinder head applications. The use of studs, as opposed to bolts, for cylinder head installation provides a more accurate and uniform clamping load pattern throughout the cylinder head.</p>

Main studs

For a performance or heavy-duty application, the use of studs is preferred whenever possible instead of main cap bolts, in those instances where a choice is available. Studs provide the ability to obtain much more accurate torque values because the studs don’t twist during tightening as do bolts. Because the studs remain stationary during nut tightening, the studs stretch in one axis alone, providing much more even and accurate clamping forces. Also, because the use of studs results in less wear applied to the block’s threads, this extends the life of the threaded holes in the block over periods of servicing/rebuilding. This is especially important when dealing with alloy blocks. The use of studs also eases main cap installation, and contributes to main cap alignment. There is less chance of main cap walking because the studs remain stationary during cap clamping.

Here a set of main studs is installed finger-tight into a GM LS block.
<p>Here a set of main studs is installed finger-tight into a GM LS block.</p>

Aftermarket performance studs usually feature a female hex which allows easy installation and removal using a hex wrench.
<p>Aftermarket performance studs usually feature a female hex which allows easy installation and removal using a hex wrench.</p>

Main cap stud installation tips

Before installation begins, clean the block, the caps and the studs thoroughly. Any debris on the threads can easily affect thread engagement quality and can cause incorrect torque wrench readings.

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