Mitsubishi 3000GT 1991, Service Manual

Page: 86 / 1146

ENGINE
Cylinder Head and Valve
VALVE SPRINGS
Check free length of each valve spring and replace if
necessary.
Standard value: 46.9 mm in.)
Limit: 45.9 mm in.)
(2) Using a square, test squareness of each valve spring. If
spring is excessively out of square, replace it.
Standard value: Less than 2”
Limit: 4
1 EN035
VALVE GUIDES
Check the valve stem-to-guide clearance. If the clearance
exceeds the service limit, replace the valve guide with new
oversize part.
Standard value:
Intake
Exhaust 0.02 0.05 mm in.)
Limit:
0.05 0.09 mm in.)
Intake
Exhaust
0.10 mm in.)
0.12 mm in.)
1
VALVE SEAT RECONDITIONING PROCEDURES
Before valve seat reconditioning, check valve stem to guide
clearance.
Recondition the valve seat with a seat grinder or cutter. The
valve seat width should be the specified value at the center
of the valve face.
Inspect the valve seat with prussian blue to determine
where the valve contacts the seat. To do this, coat valve
seat lightly with prussian blue, and then set valve in place.
Rotate the valve with light pressure. If the blue is
transferred to the center of valve face, contact is satisfac-
tory.
If the blue is transferred to top edge of the valve face, lower
valve seat with a 30 degrees stone or cutter. If the blue is
transferred to the bottom edge of valve face, raise valve
seat with a 65 degrees stone or cutter.
Valve seat diameter:
Intake
34 mm in.)
Exhaust
Seat width: 0.9
29.5 mm in.)
mm in.)
(3) The valve and valve seat should be lapped with a lapping
compound.
VALVE SEAT REPLACEMENT PROCEDURE
(1) Grind the valve seat to be replaced from the inside to thin
the wall thickness. Then, remove the valve seat.
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