Valves and valve seat inspection

Inspection of the condition of valves and the valve seats is performed after disassembling the cylinder head and removing the valve. This is a mandatory procedure before assembling the cylinder head.

Valves and valve seats work in very poor conditions, and they should be carefully inspected each time the cylinder head is removed from the engine. Valves can burn or deform, leading to problems with lack of ignition. Also, the top of the valve can wear out due to a lack of lubrication, which leads to a knocking sound. The valve stem can wear out, which leads to the penetration of engine oil into the engine cylinder.

After removing the valve from the cylinder head, the valves and seats should be visually inspected for cracks, burn marks, signs of leakage, and damage to the valve face, stem, and tip. If any of the problems are detected, the valve must be replaced and the seat will be replaced or repaired depending on the degree of damage. If there are no obvious visual defects, then the valve and seat are measured and compared with specific values.

The diameter of the valve stem should be measured in the part that passes through the valve guide. The measurement is performed with a micrometer and the measurement results are compared with those given in the service specifications. Some valves come with a pointed valve stem, where the end of the stem is slightly narrower next to the valve head to allow the stem to expand on warmer engines. Valve margins are measured with a machinist’s rule to ensure they are within specifications. It also measures the width of the valve seat and compares it to specifications.

For valves and valve seats inspection, follow these steps:

Visual inspection of the valve

Visually inspect each valve for signs of burning, warping, and excessive wear on the face, stem, and tip. If found, replace the valves with new ones.

Visual inspection of the valve seat

Visually inspect each valve seat for signs of burning, leaks, or excessive wear. If found, the seat must be machined or replaced.

Measure valve stem diameter

Use a micrometer to measure the diameter of the tree of all valves in three places in the part that passes through the valve guide and calculate the average value. Compare the measured values with the specifications and determine the necessary actions.

Margin measurement

Measure the valve margin with a machinist’s rule and record the readings. Measure the width of the valve seat with a machinist’s rule and record the readings. Compare the measured values with the specifications and determine the necessary actions.