Lycoming Compression Check

Lycoming Compression Check FAQ

What should the compression reading be on a lycoming engine?

Lycoming’s guidelines specify that each cylinder’s compression reading should be above 70/80, and within 5 psi of the engine’s other cylinders. When compression readings fall below 70/80, Lycoming says that’s the result of wear and should be further evaluated.

When to use lycoming si 1191a compression test?

During a scheduled or unscheduled maintenance of the engine (such as an oil change), visually inspect between the cooling fins and/or for exhaust stains on the cooling fins for cracks, and perform a compression check using Lycoming SI 1191A, dated September 28, 1998, or later revision.

Are there any cracks in the cylinder on a lycoming engine?

According to the SAIB, The FAA has received reports of cylinders cracking on Lycoming engines, excluding Lycoming 0-235 series engines, between the 14th and 15th cylinder cooling fins on the intake valve side of the cylinder. Cracks may occur at any time.

What is a compression test on an engine?

Compression testing Compression testing is basically a test to determine the amount of leakage past the piston rings and valves in an engine cylinder. The type of compression test used for aircraft engines is a differential compression test. This is somewhat different from a direct compression test commonly used in testing automotive engines.