Figure 6-5. Removing Valve Seat Insert With Puller

TM 10-3930-623-34

6-27. EXHAUST VALVE INSERT SEATS. The exhaust

4. Grind valve seat angle with suitable valve seat

valve is mated to a valve seat insert (3, figure 4-23) fitted

grinding tool having a long taper pilot to insure accurate

with an 0.003 to 0.005 inch interference fit to the cylinder

seat to bore. After grinding with pilot still in position, use

block. Replace exhaust valve seats as follows:

a dial indicator to check concentricity of valve seat.

Runout must not be more than 0.002 inch.

1. Use suitable valve seat puller to remove any

loose or defective valve seat, (see figure 6-5).

6-28. INTAKE VALVE SEATS. Grind intake valve seat

Replacement seats are available in 0.010 inch oversize.

in cylinder block the same as the exhaust valve insert

seat. See step 4 above.

NOTE

Always replace valve seat with one

NOTE

0.010 inch more oversize than that

The seat angle for the Continental

removed.

Model F244, Standardized Military

engine is 45 deg for both intake and

2. Use a suitable valve seat counterbore tool to

exhaust valves.

enlarge valve seat bore sufficient to obtain 0.003 to

0.005 inch tight fit (bore less than valve seat outside

6-29. VALVE REPAIRS . Repairs to valves consists

diameter). Counterbore to full depth.

only of refacing the valve face with a suitable valve

grinder tool.

NOTE

Complete counterbore drilling before

1. Grind Continental Model F244, Standardized

starting to reassemble engine to

Military Engine intake and exhaust valves to a 45 deg

prevent chips from falling into

seat angle.

engine.

If the engine is not

completely disassembled, pack valve

2. Check that new contact face concentricity is

chambers with rags to prevent chips

within 0.002 inch with valve stem when checked with a

from falling into oil pan.

dial indicator and "V" blocks. If not, reface.

3. Chill valve seat insert in a container of dry ice for

NOTE

20 minutes. After chilling, position guide in cleaned

If the parallel sides of valve head

counterbore and with suitable driver, tap in position with

(area above seat angle) is reduced to

light hammer. Excessive force may shear sidewall of

less than one-half the original height,

counterbore. Make sure seat is bottomed before it

replace valve.

warms.

6-30. VALVE FACE TO VALVE SEAT CONTACT.

CAUTION

Valves will fail prematurely due to burning, warpage or

Do not touch dry ice with bare hands.

other damage, if the valve to valve seat contact is

It will cause frost-bite due to its

incorrect. Check contact as follows:

extreme low temperature.

1. Lightly coat valve seat with Prussian blue.

Assemble valve to cylinder block and rotate slightly to

obtain "pattern". Remove valve.

2. Transferred blue line on valve shall be between

1/16 and 3/32 inch wide and positioned so at least 1/64

inch is clear on both sides. If blue runs off either or both

sides correct as follows:

a. Head side. Regrind valve seat with a 15

deg stone to reduce seat face diameter.

b. Stem side. Regrind valve seat with a 60

deg to 75 deg stone to increase inner seat diameter.

Figure 6-5. Removing Valve Seat Insert With Puller

6-6