Engine Break-in Procedure (Engine test runs)
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Proper engine break in will produce an engine that achieves maximum power output with the least amount of oil consumption.  When the piston rings are properly broken-in, they keep combustion gases in the combustion chamber and prevent gases escpaing past the piston rings into the crankcase section of the engine.  This reduced "blow-by" keeps your engine running cleaner and cooler.  Excessive "blow-by" increases crankcase pressure and contaminates the oil with combustion gases.  Also, if the rings do not seat properly, they cannot keep excess oil off the cylinder walls.  The result is an engine that consumes more than its share of oil.

When a cylinder is overhauled, the surface of it's walls are honed with abrasive stones to produce a rough surface that will help wear-in (seat) the piston rings.  This honing process creates a "cross-hatch" scratching on the cylinder walls.   When the engine is being "broken-in" the face of the piston ring rubs against the cross-hatch surface of the cylinder wall causing wear on both the rings and cylinder.  When the rings and the cylinders have worn into each other, break-in has occurred.

During the first few test runs, keep the temperatures to a minimum while providing an opportunity to check for leaks and verify the installation is airworthy. During these first few test runs, the engine RPMs and engine temps are gradually increased. These runs put very little pressure on the rings; ring break-in is not the objective. Rather, these engine runs let the cam, lifters, main and rod bearings, and all the other moving parts, get to know each other. Take your time and follow these steps.

Installation Checkout
Engine Test Runs
Flight Test
Post Flight

First Engine Run/Setup: 800 RPM   (Check for IDLE RPM)

1. Start and run the engine for one (1) minute at 800 RPM. 

. . Observe oil pressure, oil temperature, fuel pressure, and alternator output.
2. Move throttle to IDLE.  Check IDLE RPM.  Shut down.

. . Check for leaks.  Allow engine to cool for 10 to 15 minutes. 

3. Make small adjustment to IDLE RPM as necessary.

Second Engine Run/Setup: 1000 RPM  (Check Magneto P-leads)

1. Start and run engine for four (4) minutes at 1000 RPM.

. . Observe oil pressure, oil temperature, fuel pressure, and alternator output.
2. Do a quick magneto check.  We're just checking to make sure the P-leads are connected and working.

3. Move throttle to IDLE.  Check IDLE RPM.  Shut down.

. . Check for leaks.  Allow engine to cool for 10 to15 minutes. 

4. Make small adjustment to IDLE RPM as necessary.

Third Engine Run/Setup: 1200 RPM  (Check Oil pressure/temperature, fuel pressure, alternator and IDLE Cut-Off)

1. Start and run engine for one (1) minute at 1000 RPM.

2. Move throttle to IDLE.  Check IDLE RPM.

3. Advance throttle to 1200 RPM.  Maintain 1200 RPM for five (5) minutes.
. . Observe oil pressure, oil temperature, fuel pressure, and alternator output.
4. Reduce power to idle, observe idle speed.
5. Pull mixture out slowly to shut off fuel.  Observe tachometer for RPM rise.  Engine Shut-down.
. . a. Carbureted engines: 25 to 50 RPM increase.
. . b. Fuel Injected engines: 20 to 30 RPM increase.   
6. Inspect engine for oil and fuel leaks
7. Make small adjustments to IDLE and mixture as necessary.
8. Let the engine cool completely in preparation of next run

Fourth Engine Run/Setup: 1800 RPM  (Magneto RPM drop)

1. Start and run engine for one minute at 1000 RPM.

2. Move throttle to IDLE.  Check IDLE RPM.

3. Advance throttle to 1200 RPM for five (5) minutes. 
. . Observe oil pressure, oil temperature, fuel pressure, and alternator output.
4. Advance throttle to 1800 RPM.
5. Perform magneto check.  Note the RPM change for each magneto.
6. On aircraft with controllable pitch prop:

. . a. Pull prop control out for 10 seconds (maximum). Observe oil pressure.
. . b. Go back to full increase.
. . c. Note: Check prop as little as possible because cycling of prop robs engine of oil.
7. Reduce engine RPM to 1200 RPM for two (2) minutes.

8. Reduce engine to IDLE. 
9. Slowly move mixture to IDLE cuttof.   Observe tachometer for RPM rise.   Engine Shut-down.

10. Inspect engine for oil and fuel leaks
11. Make small adjustments to IDLE and mixture as necessary.
12. Let the engine cool completely in preparation for final test run.

Final Engine Run/Setup: Static RPM  ()

1. Preheat engine as required (if it's less than 50 degrees ouside.)
2. Start and run engine for one minute at 1000 RPM.

3. Advance throttle to 1200 RPM for five (5) minutes. 
. . Observe oil pressure, oil temperature, fuel pressure, and alternator output.
4. Advance throttle to 1800 RPM.
5. Perform magneto check.  Note the RPM change for each magneto.
6. On aircraft with controllable pitch prop:

. . a. Pull prop control out for 10 seconds (maximum). Observe oil pressure.
. . b. Go back to full increase.

. . c. Note: Check prop as little as possible because cycling of prop robs engine of oil.
4. Reduce engine speed to 1500 RPM.

5. Maintain 1500 RPM until the oil temperature is above 100 degrees F.
6. Run engine to full static airframe recommended power for a period not to exceed 10 seconds.
7.
Reduce power to 1200 RPM for five minutes as a cool down period.
8. Reduce throttle to idle.  Check idle RPM, check idle mixture, then shut engine down.
11. Inspect engine for leaks and make necessary adjustments.
12. Remove oil filter and inspect element or remove oil pressure screen and check for contamination.
13. If no contamination is evident, the aircraft is ready for flight check

I usually drain the oil and add new at this time.   New filter too.