Blogging / Grayscale / Michigan Checking the Compression 28th July 2019 John My dad check’s that the 1910 cylinder still has compression. Spark plugs in those days were 18mm instead of the smaller size we use today. Share this:Click to share on LinkedIn (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on Twitter (Opens in new window)Like this:Like Loading...