From the L-Head service manual:
[FONT="]Valve Seats[/FONT] Valve seats are not replaceable. If they are burned, pitted, or distorted they can be reground using a grinding stone or avalve seat cutting tool. Valve seats are ground to an angle of 46 degrees. Check the specifications section for properwidth.
The recommended procedure to properly cut a valve seat is to use the Neway Valve Cutting System, which consistsof three different cutters. LEV engines have a small combustion chamber and require the use of a special Newaycutter #103 for the 46 and 31 degree combination cutter. The 60 degree cutter is Neway cutter #101. The taperedpilots 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 valveseats on the LEV engine, the seat cutter will make simultaneous contact with the seat and the aluminum portion of theengine block. There is no detrimental effect to performance or life of the valve seat or block from the procedure.
First, use the 60 degree cutter to clean and narrow the seat from the bottom to the center (diag. 43).Second, use the 31 degree cutter to clean and narrow the seat from the top toward the center (diag. 44).Third or last, use the 46 degree cutter to cut the seat to a width of 3/64" (1.191 mm) (diag. 45).
[FONT="]Valve Seats[/FONT] Valve seats are not replaceable. If they are burned, pitted, or distorted they can be reground using a grinding stone or avalve seat cutting tool. Valve seats are ground to an angle of 46 degrees. Check the specifications section for properwidth.
The recommended procedure to properly cut a valve seat is to use the Neway Valve Cutting System, which consistsof three different cutters. LEV engines have a small combustion chamber and require the use of a special Newaycutter #103 for the 46 and 31 degree combination cutter. The 60 degree cutter is Neway cutter #101. The taperedpilots 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 valveseats on the LEV engine, the seat cutter will make simultaneous contact with the seat and the aluminum portion of theengine block. There is no detrimental effect to performance or life of the valve seat or block from the procedure.
First, use the 60 degree cutter to clean and narrow the seat from the bottom to the center (diag. 43).Second, use the 31 degree cutter to clean and narrow the seat from the top toward the center (diag. 44).Third or last, use the 46 degree cutter to cut the seat to a width of 3/64" (1.191 mm) (diag. 45).
A bigger bore block makes hopping up easier.
Stock seats should be able to accept larger valves. Throat ID around 87% of head diameter is typical.
30 degree intake flows more at low lifts, allows a lighter valve.
If there's enough material in the aluminum, the block can be cut to install round insert seats.
Doing intake side first, the exhaust seat can intrude in to the intake one, if they would otherwise overlap.
Stock seats should be able to accept larger valves. Throat ID around 87% of head diameter is typical.
30 degree intake flows more at low lifts, allows a lighter valve.
If there's enough material in the aluminum, the block can be cut to install round insert seats.
Doing intake side first, the exhaust seat can intrude in to the intake one, if they would otherwise overlap.