Throwback to working on my World War II era Ford 2N tractor and two cylinders had no compression. It turned out not to be anything catastrophic. Someone simply forgot to install the valve retainer clips. That’s the beauty of old equipment. Everything is simple, accessible, and logical. I was able to pull the head in about 20 minutes and immediately see the problem.No computers, no scan tools, no mystery. Just basic mechanical systems that can be diagnosed with your eyes and fixed with hand tools