Service Manual

5.32
ENGINE
Valve Seat Reconditioning
Valve seat reconditioning should be performed by a technician
proficient in cylinder head reconditioning techniques.
Reconditioning techniques vary, so follow the instructions
provided by the valve reconditioning equipment manufacturer.
Do not grind seats more than necessary to provide proper seat
surface, width, and contact point on valve face.
Valve Seat Inspection
Inspect valve seat in cylinder head for pitting, burnt spots,
roughness, and uneven surface. If any of the above conditions
exist, the valve seat must be reconditioned. If the valve seat is
cracked the cylinder head must be replaced.
Valve seat width and point of contact on the valve face is very
important for proper sealing. The valve must contact the valve
seat over the entire circumference of the seat, and the seat must
be the proper width all the way around. If the seat is uneven,
compression leakage will result. If the seat is too wide, seat
pressure is reduced, causing carbon accumulation and possible
compression loss. If the seat is too narrow, heat transfer from
valve to seat is reduced. The valve may overheat and warp,
resulting in burnt valves.
1. Install pilot into valve guide.
2. Apply cutting oil to valve seat and cutter.
3. Place 46
° cutter on the pilot and make a light cut.
4. Inspect the cut area of the seat:
* If the contact area is less than 75% of the circumference of the
seat, rotate the pilot 180
° and make another light cut.
* If the cutter now contacts the uncut portion of the seat, check
the pilot. Look for burrs, nicks, or runout. If the pilot is bent it
must be replaced.
* If the contact area of the cutter is in the same place, the valve
guide is distorted from improper installation
* If the contact area of the initial cut is greater than 75%,
continue to cut the seat until all pits are removed and a new seat
surface is evident. NOTE: Remove only the amount of material
necessary to repair the seat surface.
5. To check the contact area of the seat on the valve face, apply
a thin coating of Prussian Blue™ paste to the valve seat. If
using an interference angle (46
°) apply black permanent
marker to the entire valve face (A).
6. Insert valve into guide and tap valve lightly into place a few
times.
7. Remove valve and check where the Prussian Blue
™
indicates seat contact on the valve face. The valve seat
should contact the middle of the valve face or slightly
above, and must be the proper width.
* If the indicated seat contact is at the top edge of the valve face
and contacts the margin area (B) it is too high on the valve face.
Use the 30
° cutter to lower the valve seat.
* If too low, use the 60
° cutter to raise the seat. When contact
area is centered on the valve face, measure seat width.
* If the seat is too wide or uneven, use both top and bottom
cutters to narrow the seat.
* If the seat is too narrow, widen using the 45
° cutter and re-
check contact point on the valve face and seat width after each
cut.
A