Last year at the Galesburg Fly In a friend of mine came back from his pre-takeoff engine check with a frown on his face. His engine didn’t sound right and it had a big drop on the mag check. As is the custom at Galesburg and with Stearman enthusiasts everywhere, we
all got together to help him solve his problem. Plugs were pulled, checked and installed. Leads were checked and he ran the engine again. No change. Several people tried putting their hands on the cylinders right after shutdown to determine the missing cylinder or cylinders…this is a great way to burn your hands but does not really do much else.
I have a simple and better way that I assumed everyone knew but was surprised that only a few did. I can’t take credit for the idea, because an old mechanic showed it to me years ago, but it works all the time.
First get yourself a spray bottle of water. Any old plastic squirt or spray bottle will do and water is all you will need. Next, do an engine run and when the mag or cylinder shows a drop, let it misfire that way for about 15 seconds before shutting it down. Be ready with your squirter, as soon as the engine is shut down safely, spray some water on each one of the exhaust headers as close the cylinder head as you can. The good cylinders will reward you with ¨pssst¨ sound and puff of steam, but the cool or non-firing cylinder will not. Timing is important here so be ready before the engine cools off too much. Once you identify the culprit you can try switching plugs, etc. If this does not work you may have a valve adjustment that has backed off and will need readjusting or something that will take some more serious inspecting. My friend at Galesburg had an intake valve rocker that had backed off and we adjusted it fairly quickly and off he went.
This is a simple, almost no cost method of trouble shooting that will work on any engine and it has saved me and others lots of time and trouble. Pass it on to your pals!