Q: I just bought back my original Pitts Special after 41 years. It now has a narrow deck O-360 that hasn’t been run in four years. I’m getting the PS-5C overhauled, but wonder what you think about pulling cylinders to inspect the camshaft before running it. We borescoped the cylinder walls and there appeared to be a honey-colored film on various areas.
My mentor, the great Marion Cole, used to say, “If it ain’t broke, don’t fix it.” Others have said that there are a lot of engine failures after pulling a cylinder.
A: Congratulations on bringing your original Pitts Special back home after 41 years!
Boy, you sure don’t hear about the old PS-5C pressure carburetor these days. They certainly served their purpose prior to the introduction of aircraft fuel injection and still continue to, providing they are properly operated and maintained.
Let’s get right to the question regarding the condition of the internal condition of the engine. It sounds from the information you provided that the cylinders are in good condition and show no signs of corrosion.
Just so I don’t get ahead of myself and maybe misinterpret what you said regarding the borescope inspection, may I assume the “honey-colored film” was just oil and not an indication of cylinder wall corrosion?
If there is any doubt in your mind that it may be signs of corrosion, then I’d recommend you take the cylinder with the worst indication of corrosion and remove it for a closer inspection. Close inspection of this cylinder will assist you in determining what action to take on the remaining cylinders.
Remember, once the decision is made to remove the cylinders, you are now committed to hone the cylinders and install new piston rings when reinstalling the cylinder. This also dictates following the normal engine break-in procedure when returning the engine to service. Mineral base oil should be used for this break-in procedure, as mentioned in Lycoming Service Instruction 1427B or its latest revision.
If you find yourself having to remove the cylinders, it does afford you an opportunity to conduct a closer inspection of the internal components of the engine and, in particular, the condition of the cam lobes and tappet body faces. This, as you know, is the most likely area where corrosion occurs and it may just be worth it to remove the cylinders for a closer look in this area given the fact that the engine hasn’t been run in four years.
For all those who have said there are a lot of engine failures after pulling cylinders, I’d have to say I can’t agree. If there are engine failures following cylinder removals, I’d be looking closely at the individual who did the work. Following the engine manufacturer’s recommendations and specifications, in addition to using good shop practices, including calibrated torque wrenches, will assure the work is done properly.
Eric, if Marion Cole was your mentor, you were one lucky individual. I knew Marion and helped him out in a pinch one year at Oshkosh, which he never forgot. I’m certain he’d have no problem agreeing with what I’ve stated here. He was a true gentleman and one heck of a pilot. May he rest in peace in the big hangar in the sky.