Ask the Mechanic

Engine Head Bold Tightening

(Getty Images; Photo Illustration by Barry Falkner)

READER: I have been noticing a new way of torquing head bolts after head removal. It's called the torque-turn method. This method keeps the same torque sequence but is usually done by making a light torque specification followed by a sequence of turning the head cap screw 90 degrees a specified number. What makes this way of torquing head cap screws better than torquing to a specific pound torque?

STEVE: Engine manufacturers are always interested in a better way to torque the head on an engine. The head gasket seals everything inside the engine, including high pressure, coolant and oil. Tests have shown that the torque turn method gives a more accurate and even torque across the head. This method also allows the sealing ring that holds cylinder pressure time to collapse between torque repetitions. Be careful to keep each torque trip across the head to the accurate degree of turn provided by the engine manufacturer.

One more thing: Many engine manufacturers require a final run after the engine has reached full operating temperature. This takes time to complete, but it's an important step in assuring a lasting seal. Also, check with the engine manufacturer about reusing the same head cap screws. Many are designed to stretch and are not recommended for reuse.


-- Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email, and be sure to include your phone number.