REMOVAL & INSTALLATION
Valve seat replacement should be left to an automotive machine shop, due to the high degree of precision and special equipment required. Seat replacement procedures differ between the 2.2L and 3.0L engines due to their respective aluminum and cast iron construction. The following procedures can be construed as what is generally acceptable for aluminum and cast iron cylinder heads; the actual method employed should be the decision of the machinist.
The 2.2L engine uses replaceable seat inserts. These inserts can be removed by cutting them out to within a few thousandths of their outside diameter and then collapsing the remainder, or by heating the head to a high temperature and then driving the seat out. The valve seats are integral with the cylinder head on the 3.0L engine. To install a replacement seat, the old seat must be completely cut out with a special cutter tool mounted on a cylinder head machine.
To install a new seat on the 2.2L engine, the cylinder head is usually heated to a high temperature, then the seat, which is at room temperature or slightly chilled, is pressed into the head. The head is then allowed to cool and as it does, it contracts and grips the seat. On the 3.0L engine, the new seat is usually driven in with both the head and seat at room temperature. The calculated press-fit interference retains the seat in the head.
After a new seat is installed, it must be refaced.
- Inspect the valve guides to make sure they are usable. as described under valve inspection.
- Make sure the grinding wheels on the re-facer are properly dressed to ensure a good finish.
- Grind the valve seats to a 45° angle, only removing enough metal to clean up the pits and grooves and correct valve seat runout.
- After the seat has been refaced, measure the seat width using a suitable measuring tool and compare to specification.
- If the seat is too wide, grinding wheels of 60° and 30° can be used to remove stock from the bottom and the top of the seat, respectively, and narrow the seat.
- Once the correct seat width has been obtained, find out where the seat contacts the valve. The finished seat should contact the approximate center of the valve face.
- Coat the seat with Prussian Blue and set the valve in place. Rotate the valve with light pressure, then remove it and check the seat contact.
- If the blue is transferred to the center of the valve face, contact is satisfactory. If the blue is transferred to the top edge of the valve face, lower the valve seat. If the blue is transferred to the bottom edge of the valve face, raise the valve seat.