Engine Repair and Performance Flashcards

Plastigage is used to measure which clearance?

Answer: Crankshaft and connecting rod bearing oil clearance

Plastigage is crushed between the bearing and journal to show oil clearance.

Piston ring end gap is measured by:

Answer: Squaring the ring in the cylinder bore and using a feeler gauge

The ring is pushed squarely into the bore and the gap is checked with a feeler gauge.

Excessive crankshaft end play is most likely caused by a worn:

Answer: Thrust bearing

The thrust bearing controls fore-aft crankshaft movement.

A deep knocking noise that is loudest under load and changes when a spark plug wire is disconnected on one cylinder most likely indicates:

Answer: Worn connecting rod bearing

Rod knock diminishes when the affected cylinder is disabled because load on that bearing drops.

Cylinder head warpage is checked with:

Answer: A straightedge and feeler gauge

A precision straightedge across the deck with a feeler gauge reveals warpage.

Why are the threads of a cylinder head bolt hole in an aluminum block cleaned and chased before reassembly?

Answer: To ensure accurate torque readings and proper clamping force

Debris or damaged threads cause false torque readings and uneven clamp load.

Engine oil appears milky on the dipstick. What is the most likely cause?

Answer: Coolant contamination from a failed head gasket or cracked head

Milky oil indicates coolant mixing with oil, often from a head gasket or cracked component.