EM-28 ENGINE MECHANICAL — Cylinder Head (d) Hand lap the valve and valve seat together with abrasive compound. (e) Clean the valve and valve seat after hand-lapping. 13. INSPECT VALVE SPRINGS (a) Using a steel square, check the squareness of the valve springs. Maximum: 2.0 mm (0.079 in.) If squareness is greater than maximum, replace the valve spring. (b) Measure the free height of all springs. Free height: Intake side 49.1 mm (1.933 in.) Exhaust side 52.5 mm (2.067 in.) Replace any spring that is not correct. (c) Using a spring tester, check the tension of each spring at the specified installed height. Installed height: Intake side 40.0 mm (1.575 in.) Exhaust side 43.0 mm (1.693 in.) Installed tension: Intake side 34.7 — 38.3 kg (76.5 — 84.4 lb, 340 — 376 N) Exhaust side 33.3 — 36.7 kg (73.4 — 80.9 lb, 327 — 360 N) If not within the installed tension specification, replace the spring. 14. INSPECT INTAKE, EXHAUST MANIFOLDS AND AIR IN-TAKE CHAMBER Using a precision straight edge and feeler gauge, check the surfaces contacting the cylinder head for warpage. Maximum intake warpage: 0.1 mm (0.004 in.) Maximum exhaust warpage: 0.75 mm (0.0295 in.) Maximum air intake chamber warpage: 0.1 mm (0.004 in.) If warpage is greater than maximum, replace the manifold or air intake chamber.