Valve Guide Reaming
Tools Required
J 37378-1 Valve
Guide Reamer
Important: Excessive valve stem-to-guide clearance may cause a noisy valve train,
premature valve stem oil seal wear, component damage, and/or excessive engine
oil consumption.
Insufficient valve stem-to-guide clearance will result in noisy or sticking
valves. Valves that are too tight may disturb engine smoothness or lead to
component damage.
- Measure the valve stem-to-guide clearance using a dial indicator.
Valve stem-to-guide clearance may also be obtained by using a micrometer
to measure the valve stem diameter and a ball type measuring gauge to measure
the guide bore.
- A valve stem (1) and guide
(2) with clearance in excess of 0.093 mm (0.0037 in) must be
repaired or the components replaced.
- Inspect the valve stems
for excessive scoring, wear, or warpage.
• | A valve stem that has excessive scoring (3 or 4) or wear (4 or
6) must be replaced. |
• | A valve guide that is worn and has excessive stem-to-guide clearance
should be reamed and valves with oversize stems installed. |
- Measure the valve stem diameter. A valve stem with a diameter
less than 7.95 mm (0.313 in) must be replaced. Position the
tip of the dial indicator at the top of the valve guide.
If the valve stem diameter is within specifications, and the stem-to-guide
clearance is excessive, the valve guide must be reamed oversize and a valve
with oversize stem installed.
- Ream the valve guide using
the J 37378-1
.
- Clean the guide bore of all metal shavings and debris.
- Install the valve (2) (with oversize stem) into the cylinder head (1).
- Inspect the valve for the proper fit.
Move the valve back and forth in the guide. The valve should move freely
with no resistance or drag.
Valve and Seat Grinding
Important:
• | Reconditioning the valve seats is very important. The seating
of the valves must be perfect for the engine to deliver optimum power and
performance. Several different types of equipment are available for grinding
valve seats. |
• | Another important factor is the cooling of the valve head. Good
contact between the valve and the seat will ensure that heat will be properly
dissipated. |
• | The recommendations of the manufacturer of the equipment should
be followed carefully to obtain the proper results. Regardless of what type
of equipment is used, it is essential that valve guide bores be free from
carbon or dirt to ensure proper centering of the tool pilot in the guide. |
• | Valves that are pitted must be refaced to the proper angle. Valve
stems that show excessive wear, or valves that are warped excessively must
be replaced. When a valve head that is warped excessively is refaced, a knife
edge may be ground on part or all of the valve head due to the amount of metal
that must be removed. Knife edges lead to breakage, burning or pre-ignition
due to heat localizing on this knife edge. If the edge of the valve head is
less than 1.25 mm (0.05 in) after grinding, replace the valve. |
• | Several different types of equipment are available for refacing
valves. The recommendation of the manufacturer of the equipment should be
carefully followed to obtain the proper results. |
• | DO NOT reface intake valves. Intake valves with excessive wear
or damage MUST be replaced. |
- Inspect the valve for the following:
• | Burnt or eroded areas (1) |
• | A worn or scored stem (4) |
- Inspect the valve face
for the following:
• | Worn or no margin (1 or 4) |
• | Burnt or eroded areas (3) |
- Inspect the valve margin.
The exhaust valve may be refaced if the margin is greater than 1.25 mm
(0.05 in) thick before grinding.
- Reface pitted exhaust valves on a suitable valve refacing machine.
- Replace the valve if the margin is less than 1.25 mm (0.05 in)
thick after grinding.
- If the valve face has been ground, it may be necessary to shim
the valve spring to obtain the proper spring installed height. Refer to
Cylinder Head Assemble
.
- Inspect for a loose valve
seat (9 or 11) in the cylinder head (1). The valve seat has an interference
fit to the cylinder head.
- Clean the valve guide (7) bores with a suitable tool. Remove all
carbon or dirt from the bores.
The valve guide must be clean for the seat grinding tool to obtain proper
results.
- Grind the valve seat.
The recommendations of the manufacturer of the equipment should be followed
carefully to obtain the proper results. Regardless of what type of equipment
is used, it is essential that valve guide bores be free from carbon or dirt
to ensure proper centering of the tool pilot in the guide.
- Inspect the valve seats.
• | The valve seats should be concentric to within 0.05 mm
(0.0021 in) total indicator reading. |
• | If the valve seat has been ground, it may be necessary to shim
the valve spring to attain the proper spring installed height. |