There are typically two timing marks on a Chevy 250 engine. The first mark is located on the crankshaft sprocket and indicates the number of teeth on the sprocket. This number is usually 36 or 37.
Cylinder 1 TDC mark
The second mark is located on the camshaft sprocket and indicates the cylinder number 1 top dead center (TDC). This mark is usually a small notch or line. The cylinder number 1 TDC mark is aligned with the dot on the crankshaft sprocket when the engine is at top dead center.
