Chapter
2
Part
D
General engine overhaul procedures
2D-17
in place) with moderate pressure.
9
If
it
falls through or slides through easily, the clearance is excessive
and a new piston will be required. If the piston binds at the lower end
of the cylinder and is loose toward the top, the cylinder is tapered.
If tight spots are encountered as the
gauge is rotated in
the cylinder, the cylinder is out-of-round.
1 0 Repeat the procedure for the remaining pistons and cylinders.
11 If the cylinder walls are badly scuffed or scored, or if they're
of-round or tapered beyond the limits given in the specifications, have
the engine block
and honed at an automotive machine shop.
If a
is done, oversize pistons and rings will be required.
12 If the cylinders are in reasonably good condition and not worn t o
the outside of the limits, and if the piston-to-cylinder clearances can
be maintained properly, then they don't have t o be
Honing
is all that's necessary (see Section 16).
1 3 Some four-cylinder and
six-cylinder engines are produced
with oversize or undersize components, such as oversize cylinder bores,
undersize main bearing and connecting rod journals, or oversize cam-
shaft bearing bores.
1 4 These engines are identified by a letter code stamped on the engine
block (see illustrations).
1 6 Cylinder honing
Refer to illustrations
and
1
Prior t o engine reassembly, the cylinder bores must be honed so
the new piston rings will seat correctly and provide the best possible
combustion chamber seal. Note: If you don't have the tools or don't
want
tackle the honing operation, most automotive machine shops
will do it for a reasonable fee.
2
Before honing the cylinders, install the main bearing caps and
tighten the bolts t o the specified torque.
3
Two types of cylinder hones are commonly available
the flex
hone or "bottle brush" type and the more traditional surfacing hone
with spring-loaded stones. Both will do the job, but for the less exper-
ienced mechanic the "bottle brush" hone will probably be easier t o
use. You'll also need some kerosene or honing oil, rags and an elec-
tric drill motor. Proceed as follows:
4
After the honing job is complete, chamfer the top edges of the
cylinder bores with a small file so the rings won't catch when the
pistons are installed. Be very careful not t o nick the cylinder walls with
the end of the file.
5
The entire engine block must be washed again very thoroughly
with warm, soapy water t o remove all traces of the abrasive grit pro-
duced during the honing operation. Note: The bores can be considered
clean when a lint-free white cloth
dampened with clean engine oil
used to wipe them out doesn't pick up any more honing residue,
which
up as gray areas on the cloth. Be sure t o run a brush
through all oil holes and galleries and flush them with running water.
6
After rinsing, dry the block and apply a coat of light rust preventive
oil to all machined surfaces. Wrap the block in a plastic trash bag t o
keep it clean and set it aside until reassembly.
Mount the hone in the drill motor, compress the stones (if ap-
plicable) and slip it into the first cylinder (see illustration). Be sure
to wear safety goggles or a face shield!
Lubricate the cylinder with plenty of honing oil or kerosene, turn
on the drill and move the hone up-and-down in the cylinder at
a pace that will produce a fine crosshatch pattern on the cylinder
walls. Ideally, the crosshatch lines should intersect at approx-
imately a
angle (see illustration). Be sure t o use plenty of
lubricant and don't take off any more material than is absolutely
necessary t o produce the desired finish. Note: Piston ring
manufacturers may specify a smaller crosshatch angle than the
traditional 60
-
read and follow any instructions included with
the new rings.
Don't withdraw the hone from the cylinder while it's running.
Instead, shut off the drill and continue moving the hone
down in the cylinder until
it
comes to a complete stop, then com-
press the stones and withdraw the hone. If you're using a "bottle
brush" type hone, stop the drill motor, then turn the chuck in
the normal direction of rotation while withdrawing the hone from
the cylinder.
Wipe the oil out of the cylinder and repeat the procedure for the
remainina cvlinders.
A "bottle brush" hone will produce better results i f
you have never done cylinder honing before
The cylinder hone should leave a smooth,
crosshatch pattern w i t h the lines intersecting at
approximately a 60-degree angle
1 7 Pistonslconnecting rods
-
inspection
Refer to illustrations 1
1
1 7. 10, 1
7. 1
and 1 7. 1
1
Before the inspection process can be carried out, the
rod assemblies must be cleaned and the original piston rings
removed from the pistons. Note: Always use new piston rings when
the engine is reassembled.
2
Using a piston ring installation tool, carefully remove the rings from
the pistons. Be careful not t o nick or gouge the pistons in the process.
3
Scrape all traces of carbon from the top of the piston. A hand-
held wire brush or a piece of fine emery cloth can be used once the
majority of the deposits have been scraped away. Do not, under any
circumstances, use a wire brush mounted in a drill motor t o remove
deposits
the pistons. The piston material is soft and may be eroded
away by the wire brush.
4
Use a piston ring groove cleaning tool t o remove carbon deposits
from the ring grooves. If a tool isn't available, a piece broken off the
old ring will do the job. Be very careful t o remove only the carbon
deposits
don't remove any metal and do not nick or scratch the sides
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