By Lee Beery


This material based on Lycoming Service Letter #1427 and conversations with Lycoming Service Reps and applies to 2150's and 2180's cylinder changes, engine overhauls and re-manufactured engines.


The objective of engine/cylinder break-in is to obtain a gas and oil seal between the cylinder walls and piston rings while keeping other engine friction to a minimum.  We should use straight mineral oil for at least the first 50 hours or longer before changing over to an ash-less dispersant.  Cowling and baffles must be in place to ensure optimum cooling even for any short ground runs (not to exceed four minutes).  Shut down using magneto switch then inspect engine for leaks.  The first 50 hours of flight procedures are as follows:


1.   Start engine and perform normal run-up. Take off and monitor oil pressure and

     temperature.(Many Vargas do not have cylinder head temp gauges, but now is when

     you need one ) .


2.   Assume a shallow climb angle (100 MPH suggested), and climb to 6,500 feet. Lean

     to obtain best power then enrichen the mixture approx. 50 RPM. Continue flight

     for two hours while alternating power between 65% and 75%. Monitor engine temps.


3.   At 6,500 feet, full throttle will produce 75% of the engine rated horsepower even

     though your RPM's may be right at red line. Lycoming also suggests 30 minutes of

     full power as long as engine is performing within RPM and temp limits.


4.   Descend at low cruise power. Do not reduce altitude rapidly. Also, avoid

     rapid changes in RPM's. Above all, do not let engine cool too rapidly.  Also, it

     is recommended that engine re-start should not be done until engine has cooled to

     the point that you can place your hand on the cylinder fins.


Lycoming warns that if engines are operated at low power during this critical period of time, ring break-in stops and excessive oil consumption often occurs.