1991 1999 ford explorer chilton User Manual

Use a micrometer to check the valve stem diameter
Springs, Retainers and Valve Locks
The first thing to check is the most obvious, broken springs. Next check the free length and squareness of each
spring. If applicable, insure to distinguish between intake and exhaust springs. Use a ruler and/or carpenters
square to measure the length. A carpenters square should be used to check the springs for squareness. If a
spring pressure test gauge is available, check each springs rating and compare to the...

Check the valve spring for squareness on a flat surface; a carpenters square can be used
Cylinder Head
There are several things to check on the cylinder head: valve guides, seats, cylinder head surface flatness,
cracks and physical damage.
VALVE GUIDES
Now that you know the valves are good, you can use them to check the guides, although a new valve, if
available, is preferred. Before you measure anything, look at the guides carefully and inspect them for any
cracks, chips or breakage. Also if the guide...

A dial gauge may be used to check valve stem-to-guide clearance; read the gauge while
moving the valve stem
VALVE SEATS
A visual inspection of the valve seats should show a slightly worn and pitted surface where the valve face
contacts the seat. Inspect the seat carefully for severe pitting or cracks. Also, a seat that is badly worn will be
recessed into the cylinder head. A severely worn or recessed seat may need to be replaced. All cracked seats
must be replaced. A seat concentricity gauge, if...

Checks should also be made along both diagonals of the head surface
Place a straightedge across the gasket surface. Using feeler gauges, determine the clearance at the center of
the straightedge and across the cylinder head at several points. Check along the centerline and diagonally on
the head surface. If the warpage exceeds 0.003 in. (0.076mm) within a 6.0 in. (15.2cm) span, or 0.006 in.
(0.152mm) over the total length of the head, the cylinder head must be resurfaced. After resurfacing the heads
of a...

Valves
Any valves that were not replaced should be refaced and the tips ground flat. Unless you have access to a
valve grinding machine, this should be done by a machine shop. If the valves are in extremely good condition,
as well as the valve seats and guides, they may be lapped in without performing machine work.
It is a recommended practice to lap the valves even after machine work has been performed and/or new valves
have been purchased. This insures a positive seal between the valve and seat....

Knurling is a process in which metal is displaced and raised, thereby reducing clearance, giving a true center,
and providing oil control. It is the least expensive way of repairing the valve guides. However, it is not
necessarily the best, and in some cases, a knurled valve guide will not stand up for more than a short time. It
requires a special knurlizer and precision reaming tools to obtain proper clearances. It would not be cost
effective to purchase these tools, unless you plan on rebuilding...

Certain cracks can be repaired in both cast iron and aluminum heads. For cast iron, a tapered threaded insert is
installed along the length of the crack. Aluminum can also use the tapered inserts, however welding is the
preferred method. Some physical damage can be repaired through brazing or welding. Contact a machine shop
to get expert advice for your particular dilemma.
ASSEMBLY
The first step for any assembly job is to have a clean area in which to work. Next, thoroughly clean all of the
parts and...

GENERAL INFORMATION
A thorough overhaul or rebuild of an engine block would include replacing the pistons, rings, bearings, timing
belt/chain assembly and oil pump. For OHV engines also include a new camshaft and lifters. The block would
then have the cylinders bored and honed oversize (or if using removable cylinder sleeves, new sleeves
installed) and the crankshaft would be cut undersize to provide new wearing surfaces and perfect clearances.
However, your particular engine may not have everything...

2.3L, 2.5L and 4.0L SOHC (VIN E) Engines
If not done during the cylinder head removal, remove the timing chain/belt and/or gear/sprocket assembly.
Remove the oil pick-up and pump assembly and, if necessary, the pump drive. If equipped, remove any
balance or auxiliary shafts. If necessary, remove the cylinder ridge from the top of the bore. See the cylinder
ridge removal procedure earlier in this section.
All Engines
Rotate the engine over so that the crankshaft is exposed. Use a number punch or scribe...

Carefully tap the piston out of the bore using a wooden dowel
Again, rotate the engine, this time to position the number one cylinder bore (head surface) up. Turn the
crankshaft until the number one piston is at the bottom of its travel, this should allow the maximum access to
its connecting rod. Remove the number one connecting rods fasteners and cap and place two lengths of rubber
hose over the rod bolts/studs to protect the crankshaft from damage. Using a sturdy wooden dowel and a
hammer, push the...