Stem guides and valve seats

Carefully inspect the bushings, check the uniformity of their height. If the protrusion of the sleeve is clearly different, then the sleeve has shifted and its fit is not correct (on aluminum cylinder heads, the valve bushings are pressed into the cylinder head and turned to the required clearance with the valve stem). Check bushings for cracks or other damage. Check bushing out-of-roundness and inner diameter with a bore gauge. The ovality of the sleeve is checked with a micrometer by rocking the valve in two mutually perpendicular directions (photo). If the bushing diameter and ovality differ from the norm, then the bushings must be replaced or repaired.

Valve seats

In the presence of pitting (fossae), cracks, burn marks or "indentations" replace the valve seat head. It is recommended to check the ovality of the seats with a gauge, which should not exceed the norm or 0.051 mm in the absence of relevant data. Saddles with increased ovality should be ground.