Which setup ensures an accurate flywheel runout measurement when using a dial indicator?

• A. Mount the dial indicator base to the engine block and place the pointer on the flywheel face.
• B. Mount the dial indicator base to the flywheel housing and place the pointer on the flywheel face.
• C. Mount the dial indicator base to the transmission case and place the pointer on the clutch cover.
• D. Mount the dial indicator base to the crankshaft and place the pointer on the flywheel rim.

Answer: (B)

To get an accurate flywheel runout reading, you need a fixed reference that stays true as the flywheel spins. Mounting the dial indicator base to the flywheel housing provides a solid, stationary reference that is aligned with the crankshaft, and placing the probe on the flywheel face lets the indicator track any radial deviation of the flywheel itself. If the flywheel isn’t perfectly true, the face will move toward and away from the indicator, giving a true runout measurement.

Mounting the indicator to the engine block can introduce errors because mounting surfaces may not be perfectly true or may flex, leading to inaccurate readings. Pointing the indicator at the clutch cover from the transmission case measures movement of the clutch assembly, not the flywheel, so it doesn’t reflect flywheel runout. Attaching the indicator to the crankshaft and touching the rim would involve a rotating reference, which doesn’t provide a meaningful relative movement for runout.