86
Valve Seats
Valve seats are not replaceable. If they are burned, pitted, or distorted they can be reground using a grinding stone or a
valve seat cutting tool. Valve seats are ground to an angle of 46 degrees. Check the specifications section for proper
width.
The recommended procedure to properly cut a valve seat is to use the Neway Valve Cutting System, which consists of
three different cutters. LEV engines have a small combustion chamber and require the use of a special Neway cutter
#103 for the 46 and 31 degree combination cutter. The 60 degree cutter is Neway cutter #101. The tapered pilots required
are; Neway #100-1/4-1 for the .249 (6.325 mm) exhaust guide, and Neway #100-1/4 for the .250 (6.35 mm) intake guide.
Consult the cutter's complete procedure guide for additional information.
NOTE: The valve seats are cast into the engine block at a slight angle on the LEV engines. When reconditioning valve
seats on the LEV engine, the seat cutter will make simultaneous contact with the seat and the aluminum portion of the
engine block. There is no detrimental effect to performance or life of the valve seat or block from the procedure if done
correctly.
First, use the 60 degree cutter to cut the bottom narrowing/angle. The more of bottom narrowing that is removed the
higher the contact surface will be on the valve face (closer to the margin diagram 46).
Second, use the 31 degree cutter to cut the top narrowing/angle. The more of top narrowing that is removed the lower the
contact surface will be on the valve face (away from the margin diagram 47).
Lastly, use the 46 degree cutter to cut the middle angle which is where the valve will contact the valve seat (diagram 48).
Consult the specifications pages for specific valve seat width dimensions by engine model.
49
47
46
48
CHECK VALVE
PRESSURE OUT
OIL RETURN
BAFFLE
ELEMENT
TUBE
BOTTOM
NARROWING
SEAT
15
0
60
0
BOTTOM
NARROWING
CUTTER
SEAT
TOP
NARROWING
CUTTER
31
0
46
0
FINALCUT
SEAT CUTTER
Valve Lifters
The valve lifters on some engines are different lengths. The shorter lifter is installed in the intake position and the longer
lifter is installed in the exhaust position. When removing, mark the lifters to install the lifter in the same position as it was
removed from.
Oversize Valve Guides (Pre-emmisionized Engines)
The valve guides are permanently installed in the cylinder block. If they get worn excessively, they can be reamed
oversize to accommodate a 1/32" (.793 mm) oversize valve stem.
The guides should be reamed oversize with a straight shanked hand reamer or low speed drill press. Refer to the "Table
of Specifications" (Chapter 10) to determine the correct oversize dimension. Reamers are available through your local
Tecumseh parts supplier. Consult the tool section in Chapter 11 for the correct part numbers.
The upper and lower valve spring caps must be redrilled to accommodate the oversize valve stems.
After oversizing the valve guides, the valve seats must be recut to align the valve seat to the valve guide.
CRANKCASE BREATHERS
The breather element and case can be cleaned using
cleaning solvent. Make sure the small drain hole or holes
are clean and installed facing down, so as to allow oil to
return back into the crankcase.
Top Mounted Breather
This type of breather is mounted in the top and rear of the
cylinder block in vertical shaft engines. The check valve
allows positive pressure to be vented through the element
and out the tube. Some engines have the breather tube
connected to the air cleaner assembly (diag. 49).
