When it comes to crankshaft stroke, for a lot of people that spec is a given. That is, they order a 4.0-inch-stroke crankshaft, and they know they have a four-inch stroke. However, there are a lot of situations where you might need to actually measure the stroke of a crankshaft. If it’s in the engine block, there are several tools out there that allow you to measure the piston’s movement. But, what if you don’t have that luxury?

Measuring the stroke of a crankshaft sitting on the workbench without a dedicated tool can be a tricky proposition, involving a lot of math and some eyeballing. Both of which Goodson Tools was looking to eliminate when they designed the CSG-1 Crankshaft Stroke Checking Tool. Deceptively simple in appearance, the tool uses basic geometry and a set of calipers to quickly and — most importantly — accurately measure the stroke length of a crankshaft.

The first step is to adjust the width of the legs to the spacing of your main journals via the socket-head screws at the top of the tool.

The tool itself is made from hard-anodized aluminum that will stay durable without marring your crankshaft’s journals. The legs feature an asymmetrical “V” design to center the caliper head over the centerline of both the main and rod journals while measuring, and is fully adjustable to cover a variety of journal spacing. It’s sized to work with up to 6.00 inches of stroke, and will work with almost any set of calipers. Thanks to the adjustable jaw-mounting blocks, it not only accommodates almost any calipers, but makes for an easy, one-handed operation, as the mounting blocks each have two set screws in each block, to lock onto the calipers’ jaws.

There are two set screws in each of the jaw blocks, which allow you to securely fasten the tool to the lower jaw of your caliper.

For the easiest reading, a set of digital calipers that you can zero out will work the best. But if you are in the “dials-don’t-run-out-of-batteries” camp (or even a weirdo who prefers Vernier calipers), the CSG-1 works just as well with those, albeit requiring a little bit of basic subtraction on your end. All you do is set the tool, attached to the bottom jaw of your calipers, on the main journals, sweep the top jaw over the the rod journal at the “top” of the crankshaft’s stroke and record the lowest measurement. That’s your zero. Then you repeat the process with the rod journal at the “bottom” of the crank’s throw and record the largest measurement.

Digital calipers allow you to zero out the high point of the rod journal’s travel. If you were using dial calipers, you’d simply record the lowest measurement seen.

With a digital caliper the first measurement will be “0.000” meaning the second measurement will be the crankshaft’s stroke. If your first measurement is something other than 0.000, you will subtract the first measurement from the second, and that is your crankshaft’s stroke. And that’s it. Also of note, is that while you can easily perform this check with a crankshaft standing on end, we used the Goodson PMIS-30 crankshaft stand, which made the whole process even easier.

The simple tool makes identifying crankshafts a breeze and can help prevent annoying mix-ups. Plus, it’s incredibly important to verify the accuracy of your crank’s stroke, as it is one of the most important specs of your engine.

Sweeping through the bottom of the crank’s travel will give you your stroke length directly with digital calipers. With dial calipers, you’d simply subtract your starting measurement from the measurement you get here.