Pre-ignition damage

Continental IO-360-ES piston.

TGZ-PISTON-DAMAGE-001Note the scoring on the skirt area.The very high piston temperature had caused the piston to expand so much that it was seizing in the cylinder bore. This caused the burn marks shown on the photo below.

IMG_2361The head of the piston has started to melt. Most Continental engines use pistons that have a steel insert in the area of the top ring groove.

In this case the steel insert has limited melted area of the piston, but the damage has already been done.

IMG_2363If you ever see burn marks like this on a cylinder barrel it is likely that that it has been caused by a pre-ignition event.

Piston damaged by a pre-ignition event.

IMG_2495Note how clean and free of normal combustion deposits the top of the piston is.

We never been able to work our  what caused this magneto from a Piper Chieftain to fail in the manner that it did.

IMG_2590A prize of a packet of jelly beans is on offer to who ever can explain the events that caused the distributor gear to melt.

PRECISON-POLYMER-FLOATFuel in the float chamber caused a lot of problems in these white polymer carburetor floats.

Any oil leak can be disastrous

Extruded Rod BearingExcessive main bearing clearances lead to poor oil flow to this connecting rod bearing. Very lucky that the connecting rod did not separate and cause an in flight engine stoppage.

IMG_3314The corresponding crankshaft journal. If your oil pressure drops for any reason find out why. Any loss of oil pressure is an emergency.

IMG_0896In flight oil leaks are insidious, as the oil pressure remains relatively normal until the oil level in the sump has dropped to the level of oil pump pickup. Once the oil pump starts sucking air, oil pressure is quickly lost, followed shortly thereafter by a major engine failure. Without oil pressure, connecting rods will make their way out of the crankcase.

Debris in the sump after a major engine failure.

IMG_0907Not much is salvageable from an engine after a major failure like this.

DSCN2994It wasn’t hard to identify why this Lycoming Cylinder has no compression.

DSCN3003A closer view of the exhaust valve from the cylinder.

A bent connecting rod from a Continental TSIO-520-E engine in a Cessna 402.


Over-priming caused a Hydraulic Lock and the bent connecting rod.

Main Bearing insert from a Continental IO-360-G.

DSCN3544The crankcase had fretted and lost crush on the bearing insert. This allowed the insert to move axially so that part of the shell was no longer supported by the bearing saddle and fractured.

A bad hair day for a Continental Starter Adapter.


If excessive friction in the starter motor does not allow the clutch spring to fully release, this can happen.

Transfer collars in Continental engines need to be lubricated at all times.

DSCN2135The maximum allowable clearance between the transfer collar and crankshaft is 0.0018″. Without lubrication the steel transfer collar will pick up on the steel crankshaft very quickly.

When installing a new engine or changing a propeller governor,  priming the oil gallery to the transfer collar with clean engine oil is good practice.