GMC 1982 Light Duty Truck, Руководство по обслуживанию

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SMALL BLOCK 6A4-31
bearing cap must be on the same side when installed in the
cylinder bore. If a connecting rod is ever transposed from
one block or cylinder to another, new bearings should be
fitted an d the connecting rod should be nu m b ered to
correspond with the new cylinder number.
CYLINDER BLOCK
Cleaning and Inspection
1. W ash cylinder block thoroughly in cleaning solvent and
clean all gasket surfaces.
2. Remove oil gallery plugs and clean all oil passages.
3. Clean and inspect coolant passages in the cylinder
block.
4. Inspect the cylinder block for cracks in the cylinder
walls, coolant jac k e t, valve lifter bores and main
bearing webs.
5. Measure the cylinder walls for taper, out-of-round or
excessive ridge at top of ring travel. This should be done
with a dial indicator. Set the gage so th at the thrust pin
must be forced in about 1/4" (6.5mm) to enter gage in
cylinder bore. Center gage in cylinder and tu rn dial to
" 0 " . Carefully work gage up and down cylinder to
determine taper and turn it to different points around
cylinder wall to determine the out-of-round condition.
If cylinders were found to exceed specifications, honing
or boring will be necessary.
Conditioning
T he performance of the following operation is contin­
gent upon engine condition at time of repair.
If the cylinder block inspection indicated that the block
was suitable for continued use except for out-of-round or
tapered cylinders, they can be conditioned by honing or
boring.
If the cylinders were found to have less than .005"
(.13mm) taper or wear, they can be conditioned with a hone
and fitted with the high lim it s ta n d a rd size piston. A
cylinder bore of less then .005 " (. 13mm) wear or taper may
not entirely clean up when fitted to a high limit piston. If it is
desired to entirely clean up the bore in these cases, it will be
necessary to rebore for an oversize piston. If more than
.005" (.13mm) taper or wear, they should be bored and
honed to the smallest oversize th at will permit complete
resurfacing of all cylinders.
W h en pistons are being fitted and honing is not
necessary, cylinder bores may be cleaned with a hot water
an d d ete rg e n t wash. A fter cleaning, th e cylinder bores
should be swabbed several times with light engine oil and a
clean cloth and then wiped with a clean dry cloth.
Boring
1. Before using any type boring bar, the top of the
cylinder block should be filed to remove any dirt or
burrs. This is very important. If not checked, the boring
bar may be tilted which would result in the rebored
cylinder wall not being a t rig h t angles to the
crankshaft.
2. The piston to be fitted should be measured with a
micrometer, measuring at the center of the piston skirt
and at right angles to the piston pin. The cylinder
should be bored to the same diameter as the piston and
honed to give the specified clearance.
3. The instructions furnished by the m anufacturer of the
equipment being used should be carefully followed.
Honing
1. W hen cylinders are to be honed, follow the hone
m an u factu rer’s recommendations for the use of the
hone and cleaning and lubrication during honing.
2. Occasionally during the honing operation, the cylinder
bore should be thoroughly cleaned and the piston
selected for the individual cylinder checked for correct
fit.
3. When finish honing a cylinder bore to fit a piston, the
hone should be moved up and down at a sufficient speed
to obtain very fine uniform surface finish marks in a
cross-hatch pattern of approximately 45° to 65° in­
cluded angle. The finish marks should be clean but not
sharp, free from imbedded particles and torn or folded
metal.
4. Permanently m ark the piston for the cylinder to which
it has been fitted and proceed to hone cylinders and fit
the remaining pistons.
NOTICE: H a n d le the pistons with care and do not
a ttem pt to force them through the cylinder until the
cylinder has been honed to correct size as this type
piston can be distorted through careless handling.
5. Thoroughly clean the bores with hot w ater and deter­
gent. Scrub well with a stiff bristle brush and rinse
thoroughly with hot water. It is extremely essential th at
a good cleaning operation be performed. If any of the
abrasive material is allowed to remain in the cylinder
bores, it will rapidly wear the new rings and cylinder
bores in addition to the bearings lubricated by the
contaminated oil, the bores should be swabbed and then
wiped with a clean dry cloth. Cylinder should not be
cleaned with kerosene or gasoline. Clean the remainder
of the cylinder block to remove the excess material
spread during the honing operation.
Piston Selection
1. C heck U S E D piston to cylinder bore cle a ra n ce as
follows:
a. M easu re the "C y lin d er Bore D i a m e te r " with a
telescope gage | 2 - 1/2" (64mm) from top of cylinder
bore]).
b. M e a su re the "P isto n D i a m e te r " (a t skirt across
center line of piston pin).
c. S ubtract piston diameter from cylinder bore diam e­
ter to determine " Piston to Bore Clearance ".
d. Locate piston to bore clearance on Piston Selection
C h a rt and determine if piston to bore clearance is in
the acceptable range.
2. If used piston is not acceptable, determine if a new
piston can fit cylinder bore.
3. If cylinder bore must be reconditioned, measure new
piston diam eter (across center line of piston pin) then
hone cylinder bore to correct clearance.
4. M ark the piston to identify the cylinder for which it
was fitted.