895126 Mercury COLLAR, (6 mm)

Cylinder Heads With Guides New cylinder heads have been introduced on the 4.236 engine. The new heads have replaceable valve guides. The differences between the earlier and current heads are explained below. The change became effective at engine serial number LD70178U040236M and up. The engine serial number is located above the fuel injection pump on the block.(1) Outer spring: Length under test force ... 27.4 mm (1.08 in)Test force ... 180 9 N (40 2 lb)Free length after test ... 45.2 mm (1.78 in)(Damper coils of spring go toward cylinder head).(2) Inner spring: Length under test force ... 23.88 mm (.940 in)Test force ... 69 9 N (15.4 2 lb)Free length after test ... 39.6 mm (1.56 in)(Damper coils of spring go toward cylinder head).Earlier Cylinder Heads Without Removable Guides
(3) Exhaust valve stem diameter ... 9.449 to 9.469 mm (.372 to .3728 in) Valves are available in stem oversizes of 0.08, 0.38 and 0.76 mm (.003, .015 and .030 in).Exhaust valve overall length ... 123.11 to 123.52 mm (4.847 to 4.863 in)Bore in cylinder head for valve ... 9.506 to 9.531 mm (.37425 to .37525 in)Clearance between valve stem and bore ... 0.0368 to 0.0826 mm (.00145 to .00325 in)Maximum permissible clearance between valve stem and bore ... 0.15 mm (.006 in)(4) Intake valve stem diameter ... 9.462 to 9.487 mm (.3725 to .3735 in) Valves are available in stem oversizes of 0.08, 0.38 and 0.76 mm (.003, .015 and .030 in).Intake valve overall length ... 122.71 to 123.11 mm (4.831 to 4.847 in)Bore in cylinder head for valve ... 9.506 to 9.531 mm (.37425 to .37525 in)Clearance between valve stem and bore ... 0.0191 to 0.0699 mm (.00075 to .00275 in)Maximum permissible clearance between valve stem and bore ... 0.13 mm (.005 in)Current Cylinder Heads With Removable Guides
(5) Valve guides: Inside diameter ... 9.507 to 9.543 mm (.3743 to .3757 in)Outside diameter ... 15.921 to 15.933 mm (.6268 to .6273 in)Parent bore diameter in cylinder head for valve guide ... 15.867 to 15.893 mm (.6247 to .6257 in)Interference fit of guide in cylinder head ... 0.028 to 0.066 mm (.0011 to .0026 in)Overall length of guide:Intake ... 57.94 mm (2.281 in)Exhaust ... 61.11 mm (2.406 in)Projection of guide above valve spring recess ... 15.09 mm (.594 in)(6) Exhaust valve stem diameter ... 9.449 to 9.468 mm (.372 to .3728 in) Clearance of valve in guide ... 0.058 to 0.119 mm (.0023 to .0047 in)Maximum permissible clearance of valve in guide ... 0.13 mm (.005 in)Exhaust valve overall length ... 123.11 to 123.52 mm (4.847 to 4.863 in)(7) Intake valve stem diameter ... 9.462 to 9.487 mm (.3725 to .3735 in) Clearance of valve in guide ... 0.058 to 0.119 mm (.0023 to .0047 in)Maximum permissible clearance of valve in guide ... 0.13 mm (.006 in)Intake valve overall length ... 122.71 to 123.11 mm (4.831 to 4.847 in)All Cylinder Heads
(8) Exhaust valve face angle ... 45°Valve seat angle ... 45°(9) Exhaust valve head diameter ... 36.45 to 36.70 mm (1.435 to 1.445 in) Thickness of valve lip (between runout of valve seat and face of valve) ... 0.79 mm (.031 in)Valve depth below cylinder head face:Minimum ... 1.19 mm (.047 in)Maximum ... 1.45 mm (.057 in)Service wear limit ... 1.85 mm (.073 in)(10) Intake valve head diameter ... 44.09 to 44.35 mm (1.736 to 1.746 in) Thickness of valve lip (between runout of valve seat and face of valve) ... 0.79 mm (.031 in)Valve depth below cylinder head face:Minimum ... 0.89 mm (.035 in)Maximum ... 1.14 mm (.045 in)Service wear limit ... 1.55 mm (.061 in)(11) Intake valve face angle ... 45°Valve seat angle ... 45°Exhaust valve seat insert (for service): (12) Angle to grind flare of valve seat ... 30°(13) Maximum permissible depth of the bore to grind the flare of the exhaust valve seat ... 2.39 to 2.51 mm (.094 to .099 in) (14) Production engines do not have an exhaust valve seat insert, but can be installed for service. The dimensions to machine the recess in the head are as follows: A ... 9.53 to 9.65 mm (.375 to .380 in)B ... 42.62 to 42.65 mm (1.678 to 1.679 in)C (Radius) ... 0.38 mm (.015 in)