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Engine Building 101: How and Why to Perform an Engine Friction Test (Video)

What is an engine friction test and why would you want to perform one?

When building a short block, a friction test will help you determine the amount of drag your rotating assembly is producing so you can minimize it — and it’s effect on performance.

Additionally, a friction test can help you test your rotating assembly and locate tight spots within the setup.

In this Engine Building 101 video, we’ll show you how to perform a friction test on an engine stand and determine rotating or piston drag. The lower the number, the faster the acceleration and power.

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  1. Pingback: Engine Building 101: How and Why to Perform an Engine Friction Test (Video)

  2. Bart Logan says:

    How can you accurately perform a friction test on a newly assembled short block? Won’t your readings be affected by the lack of “break-in” and the support of engine oil, under pressure, at the bearing surfaces as well as the differences in clearances between room temperature and operating temperature? If the machine work was done properly, the correct components used to obtain the specified clearances, etc., is there a real purpose to even perform a friction test?

  3. Is there a purpose? Yes. In the case of a short block, it should rotate smoothly. Albeit there will be some drag, but it should not have tight spots or weirdness during the rotation.
    Just the opinion of some 60+ backyard idiot

  4. Bart Logan most of what you said is 100% correct but they are not looking at those items. They want to build u information on a particular engine or engine family. As long as they do it the same every time it is valuable data. The few people that have electric dynamometers use that feature on damn near every power run. The others use a fudge factor they take a SWAG (Scientific Wild Ass Guess) at what the rotational friction numbers are and used that in the horsepower correction factors. Rotational friction explains how two of the same engines coming off the same line make different power. A very important but commonly misunderstood factor in engine development.

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