CYLINDER HEAD—E.5Fig. E.7. Press Tool for Valve Seat Inserts.InletExhaustA— 1/16 in (1,59 mm) at 45A— 1/16 in at 45B— 3/4 in (19,05 mm)B— 3/4 inC— 0.250 in (6.35 mm)C— 0.3125 in (7,29 mm)D— 3 in (76.20 mm)D— 3 InE— 1.582 1.583 inE— 1.248/1.249 in(40,18:40,21 mm)31,70/31,72 mm)F— 2.009'2.019 inF— 1.670/1.680 in(51,03/51,28 mm)(43,32/43,76 mm)G— 1/32 in (0,79 mm) radius G— 1/32 in radiusH— 1/16 in (1.59 mm) radius H— 1/16 in radiusJ— 1/16 in (1,59 mm) at 45J— 1/16 in at 45K— 0.372:0.373 inK— 0.372/0.373 in(9,45i/9,47 mm)7.Re-cut the valve seat at an included angle of 900as in normal procedure, so that the valve headdepth below the cylinder head face is within theproduction limits given on Page B.7.NOTEIf the cylinder head face has beenskimmed since the fitting of valveseat inserts, then the following actionis permitted :(a)If the insert is in a serviceable condition,machine to the dimensions given in Fig. E.8and continue as in stages 6 and 7.(b)If the insert is damaged or unserviceablethrough wear, remove the insert and replacewith a new one, but before fitting, the back ofthe insert should be surface ground, removingthe equivalent depth of material to thatremoved by the skimming of the cylinder headface. Do not forget to re-chamfer the insert asit was prior to grinding, i.e. 0.020/0.030 in(0,508/0,762 mm) at 450. Then proceed asin stages 3 — 7.Valve SpringsValve springs deteriorate because of fatigue resultingfrom the combined effect of heat and the normal workingof the springs. After a period the spring becomes weakand is then prone to failure. This, of course, applies toall types of engines.A new set of springs should be fitted whenever theengine undergoes a major overhaul.Fig. E.8.Showing Flare to be cut at 30°.A-0.100 to 0.105 in (inlet), 0.094 to 0.099 in (exhaust).
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