Video credits go to my good friend Jimmy (Deere Jimmy on KZfaq, formerly JohnDeere318Guy). Also thanks to Ryan (Bulldog Chaser) for helping get the tractor dialed in and running strong.
After the 520 failed its first dyno test run at Rough & Tumble back in July, I wanted to try again at the Nittany Antique Machinery fall show in Centre Hall, PA a couple months later. The throttle was not opening all the way up and so I could not get the engine and governor to work under full load the first time around - this made the R&T dyno test pretty much useless since the engine was not working hard enough to get up to proper operating temperature. I made a few adjustments to the throttle linkage before the Nittany show to try and get it to open fully, but between that and the carburetor, it was still going to take some fine-tuning to get it running 100%. The engine had not been put under a significant load since it was rebuilt, and was using a little oil and smoking a little bit excessively, so it was due for a solid dyno run to break it in.
We hauled the 520 up to the show Friday afternoon (its first venture in the mountains of central PA, and a rather unusual configuration among the other tractors at the show). I hooked up to the club's 1959 M&W dyno in the morning before the line of waiting tractors got to be too long. I engaged the PTO on the 520 and let it spin the dyno slowly for a minute or two before they cranked up the load. Ryan and some of the other guys there at the booth made minor adjustments to the carburetor to lean out the fuel mixture (was smoking black like it was running too rich), and to try and push a few more RPM out of the engine to bring it up to its rated speed of 1325. With the PTO spinning at 535-540 RPM under full load, the tractor was putting out about 35-37 HP, which is right around where it should be (maybe a little bit more since the engine is pushing a slightly larger displacement).
Once we got the carb and governor adjusted properly, we let the tractor sit and run under load for a while to get the engine temperature up. Typically the coolant will run around 140-145°F when not under load. This was the first time I had seen the temp gauge climb above that range - it had no trouble reaching 185° under a WOT pull, which is ideal. We backed the load off and let it cool down for a minute or two, before loading it up again and letting it work under temperature for a few minutes more - this was done a total of 3 times. These heat cycles help to allow the piston rings to "seat" in the cylinder which will reduce oil consumption and blow-by. We did this several more times throughout the day, letting the tractor sit for a few hours in between runs and then working it until the coolant temperature would reach 185°F.
After the final run, the engine no longer smoked or showed any signs of blow-by, indicating that it had run itself in. It's likely that these few dyno runs at the show were the hardest the tractor ever worked in its life, considering it was never used for PTO work in all the years my grandfather used it on the farm. It lived a pretty easy life as a cultivating tractor and rarely saw heavy loads, so this was definitely a change of pace for it.