AERA Cylinder Head Rebuilding & Valve Train 2

Question 1

What effect does removing material from a cylinder head gasket surface (resurfacing) have on the valve train geometry of an overhead-cam engine?

Accepted Answer

It raises the camshaft relative to the head, reducing valve clearance and potentially increasing valve timing duration

Answer

It lowers the camshaft relative to the block, increasing valve clearance

Answer

It has no effect on valve train geometry because the cam is self-adjusting

Answer

It changes only the compression ratio without affecting valve timing

Question 2

Combustion chamber volume is measured to ensure uniformity across all cylinders. What is the primary reason for equalizing combustion chamber volumes?

Accepted Answer

To balance compression ratios and prevent uneven power output or detonation in individual cylinders

Answer

To maximize surface area for improved cooling efficiency

Answer

To reduce the amount of valve grinding required during rebuilding

Answer

To comply with emissions regulations for combustion efficiency

Question 3

A valve spring that measures below the minimum free-length specification should be:

Accepted Answer

Replaced, as a short free length indicates fatigue and insufficient spring pressure

Answer

Shimmed to restore the correct installed height and spring pressure

Answer

Reused if the spring rate per inch is still within spec

Answer

Tested for coil bind before making a replacement decision

Question 4

What is 'valve recession' and why is it a concern on older cast iron heads with hardened valve seats?

Accepted Answer

It is the sinking of the valve seat into the head over time, reducing valve stem height and eventually causing loss of valve adjustment

Answer

It is the withdrawal of the valve stem from the guide caused by thermal expansion

Answer

It is the erosion of the valve face caused by abrasive combustion deposits

Answer

It is the inward movement of the valve keeper grooves under spring pressure

Question 5

When selecting the correct replacement valve seat insert for a cylinder head, which dimensions are most critical?

Accepted Answer

Outside diameter, inside diameter (seat width angle), and insert height

Answer

Insert weight, material hardness, and color code

Answer

Only inside diameter, as the OD is a press-fit standard

Answer

Valve stem diameter and spring retainer groove depth

Question 6

What is the correct interference fit range for pressing a valve seat insert into a cast iron cylinder head counterbore?

Accepted Answer

0.003–0.005 in (0.076–0.127 mm)

Answer

0.010–0.015 in (0.254–0.381 mm)

Answer

0.0005–0.001 in (0.013–0.025 mm)

Answer

0.008–0.012 in (0.203–0.305 mm)

Question 7

After valve seat grinding, the seat contact pattern should be verified using:

Accepted Answer

Prussian blue or machinist's dye applied to the valve face, then lightly tapping the valve to transfer the pattern to the seat

Answer

A dial indicator measuring runout of the seat relative to the guide bore

Answer

Feeler gauges inserted between the valve and seat to check contact width

Answer

A vacuum tester applied to the port with the valve held closed by hand