20467 Mercury STUD, BOTTOM COWL TO REAR SUPPORT BRACKET

Illustration 1 g00295326
Inlet valves and exhaust valves
Double valve springs: (1) Outer spring Length under test force ... 35.8 mm (1.41 inch)Test force ... 176 to 195 N (40 to 44 lb) (2) Inner spring Length under test force ... 34.0 mm (1.34 inch)Test force ... 89 to 104 N (20 to 23 lb)Single valve springs (not shown) Length under test force ... 40.0 mm (1.57 inch)Test force ... 310 to 344 N (70 to 77 lb)Free length after test ... 53.4 mm (2.10 inch) (3) Valve spring recess for the valve spring (4) Valve guides for the inlet and exhaust valves Inside diameter ... 9.51 to 9.56 mm (0.374 to 0.376 inch)Outside diameter ... 15.900 to 15.910 mm (0.6260 to 0.6265 inch)Bore diameter in cylinder head for valve guide ... 15.87 to 15.89 mm (0.625 to 0.626 inch)Interference fit of valve guide in cylinder head ... 0.03 to 0.07 mm (0.001 to 0.003 inch)Overall length of valve guide Inlet ... 57.94 mm (2.281 inch)Exhaust ... 61.1 mm (2.406 inch)Projection of valve guide above valve spring recess (3) ... 15.1 mm (0.595 inch)Note: When new valve guides are installed, new valves and new valve seat inserts must be installed. The valve guides and the valve seat inserts are supplied as partially finished parts. The unfinished valve guides and unfinished valve seat inserts are installed in the cylinder head. Then, the guides and inserts are cut and reamed in one operation with special tooling. This procedure ensures the concentricity of the valve seat to the valve guide in order to create a seal that is tight. Refer to