Engine Break-In. Part 1.
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What is engine Break-In? Engine break-in means to introduce all of the new parts to each other in a manner that the contours of the metal matrix of the new mating surfaces form a compatible relationship with the adjacent surface. This relationship provides the least amount of wear of the two surfaces.
Cylinder Break-In. In steel, nitrided, or Cermi-Nil cylinders, the rings are the harder of the two surfaces. In chromed cylinders (which I don't recommend), the chrome surface is hard, damn hard. The rings are softer and it's the rings that need to wear.
Engine (or, more specifically, cylinder) break-in concerns itself primarily with the seating of the piston rings. With new rings in new Lycoming cylinders (never overhaul a cylinder), it becomes necessary to break-in the rings and cylinders. We want to physically wear the new piston rings into the cylinder wall for a compatible seal between the two surfaces. When the rings and the cylinders have properly worn into each other, break-in has occurred.
What oil do I use? Most engine builders use a straight mineral oil for engine break-in. BUT, for turbo-charged engines, Lycoming recommends regular Ashless Dispersant multigrade oil like AeroShell 15W-50. Why? Because they can keep a high manifold pressure. See the Flight Test Profile.
I recommend you break-in your new engine (or cylinders) with AeroShell 15W-50. I've been doing it this way since 1991.
Step 1: Pre-oiling the engine (this should take about 1/2 hour)
• Remove the top plugs.
• Magneto OFF
• Pre-oil the engine by turning the engine over using aircraft starter. Keep this to less than 30 seconds.
- You should see movement
on the oil pressure gauge.
• Let the starter cool for a few minutes. You are not in a hurry.
Repeat this step 3 more times. Watch for movement on the oil pressure gauge. Let the starter cool each time for a couple of minutes.
Step 2: Get ready to start the engine
• Let the starter cool for 20 minutes.
• Install the top plugs (while the starter is cooling).
• Check the oil level. Bring it up to 7 quarts.
• Check all connections.
• Turn on fuel boost pump. Check for leaks.
• Close the cowling. All test runs need to be made with the cowling on and closed.
Initial test run: I'm going to go out on a limb here and assume you bought an engine that was already built; preferably by LyCon Engine Rebuilders. If LyCon rebuilt your engine, there is a good chance it got a couple of hours on a test stand for initial break-in. Further, I'm going to assume you (or someone else) knew what they were doing when they installed the engine, connected all of the hoses, set the timing on the mags, filled the engine with 7 quarts (NOT 8 Quarts) of oil, and properly installed the baffles and cowling.
Step 3: Start the engine
• Turn on fuel boost pump.
• NO Primer.
- - on fuel injected engines, use the boost pump just enough to establish fuel flow (pressure)
• Throttle closed.
• Press the starter starter button.
• Be patient. It will start without priming and with the throttle closed.
• Have an observer watch for fuel or oil leaks.
This is probably the most intense part of the process.
The engine will start on about the 5th or 6th blade. Be patient.
As it starts, give it a little more throttle to keep it going.
Step 4: After the engine starts
• Adjust the throttle for an 800 to 1000 rpm engine IDLE.
• Check for 40 to 60 psi oil pressure within 30 seconds. Note: 25 psi minimum.
- - If no oil pressure, shut down the engine and determine the cause.
• If the oil pressure is good, let the engine Idle.
• Check for throttle operation.
• Check for mixture operation.
Step 5: Next step
• Shut down the engine.
• Open the cowling.
• Check for leaks.
• Check the installation of everything.
Let the engine cool for 30 minutes.
Step 6: Now on to the next step . . . . Engine Test Runs.