Cylinder Head Rebuilding & Valve Train Flashcards

When measuring valve guide inside diameter, what is the maximum acceptable clearance between the valve stem and guide for a typical intake valve on a passenger car engine?

Answer: 0.0010–0.0027 in (0.025–0.069 mm)

Typical intake valve stem-to-guide clearance for passenger car engines falls in the 0.0010–0.0027 in range; excessive clearance causes oil consumption and poor valve sealing.

What is the primary purpose of cutting a three-angle valve seat?

Answer: To narrow the contact band for better sealing and heat transfer

A three-angle valve seat narrows the seating contact band, which concentrates sealing pressure and improves heat transfer from the valve face to the seat.

When checking cylinder head flatness with a precision straightedge and feeler gauge, what is a commonly accepted maximum warpage limit for an aluminum head?

Answer: 0.002 in (0.05 mm) per 6 inches

Most specifications allow no more than 0.002 in (0.05 mm) warpage per 6 inches on aluminum heads, as aluminum is more prone to distortion and must be resurfaced if this limit is exceeded.

Valve spring installed height directly affects which critical valve train parameter?

Answer: Spring seat pressure and open pressure

Installed height determines how much the spring is compressed, setting both the closed (seat) pressure and the open pressure when the valve is fully lifted.

What condition is indicated when the valve margin (the edge between the valve face and the top of the valve head) is less than the manufacturer's minimum specification after valve face grinding?

Answer: The valve must be replaced to prevent burning or breakage

A valve margin below minimum spec creates a knife-edge condition that is prone to overheating and burning, requiring valve replacement rather than reuse.

Which method is used to verify that rocker arm geometry is correct after a cylinder head has been resurfaced?

Answer: Check that the rocker arm tip contacts the center of the valve stem tip at mid-lift

Correct rocker arm geometry requires the rocker tip to contact the valve stem tip near the center of its sweep at mid-lift, preventing side loading that accelerates wear.

When installing new valve stem seals, what is the correct procedure to prevent damage during installation on an assembled head?

Answer: Use a proper seal driver and lightly lubricate the seal lip; protect the seal over the valve stem keeper grooves with a sleeve or tape

A plastic installation sleeve or tape protects the seal lip from being cut by the sharp keeper grooves on the valve stem, and light lubrication reduces installation force without compromising sealing.