Pontiac Fiero 1988 Service Manual page 5

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VIN NUMBER PLATE
LOCATION
Fig. 2 Vehicle Identification Number Plate Location
marking indicating the strength of the material in the
fastener as outlined below. Metric cross recess screws
are identified by a Posidriv or Type 1A cross recess as
shown in Figure 6. Either a Phillips head or Type 1A
cross recess screwdriver can be used in Posidriv recess
screw heads, but Type 1A cross recess screwdrivers
will perform better.
N O T I C E :
Most metric fasteners have a blue color
coating. However, this should not be used as a
positive way of identifying as some metric fasteners
are not color coated.
General Motors Engineering Standards, along
with other North American Industries, have adopted
a portion of the standard metric fastener sizes defined
by ISO (International Standards Organization). This
was done to reduce the number of fastener sizes used
and yet retain the best strength qualities in each thread
size. For example, the customary 1/4-20 and 1/4-28
screws are replaced by the metric M6.0 X 1 screw
which has nearly the same diameter and 25.4 threads
per inch. The thread pitch is in between the customary
coarse and fine thread pitches.
Metric and customary thread notation differ
slightly. The difference is shown in Figure 9.
FASTENER STRENGTH IDENTIFICATION
Most commonly used metric fastener strength
property classes are 9.8 and 10.9 with the class
identification embossed on the head of each bolt.
Customary (inch) strength classes range from grade 2
to 8 with radial line identification embossed on each
bolt head (i.e., grade 7 bolt will exhibit 5 embossed
radial lines on the bolt head). Some metric nuts will be
marked with single digit strength identification
numbers on the nut face. Figure 10 shows the different
strength markings.
When replacing metric fasteners, be careful to use
bolts and nuts of the same strength or greater than the
original fasteners (the same number marking or higher)
.It is also important to select replacement fasteners of
the correct size. Correct replacement bolts and nuts are
available through the parts division. Many metric
fasteners available in the after-market parts channels
were designed to metric standards of countries other
than the United States. These fasteners may be of a
lower strength, different thread pitch and may not have
the numbered head marking system. The metric
fasteners used on GM products are designed to new,
international standards that may not be used by some
nondomestic bolt and nut suppliers. In general, except
for special applications, the common sizes and pitches
are:
M 6.0 X 1 M 8 x 1.25
M 10 X 1.5 M 12 X 1.75
M 1 4 X 2
PREVAILING TORQUE FASTENERS
A prevailing torque nut is designed to develop an
interference between the nut and bolt threads. This is
most often accomplished by distortion of the top of an
all-metal nut or by using a nylon patch on the threads
in the middle of the hex flat. A nylon insert may also
be used as a method of interference between nut and
bolt threads (Fig. 9).
A prevailing torque bolt is designed to develop an
interference between bolt and nut threads, or the
threads of a tapped hole. This is accomplished by
distorting some of the threads or by using a nylon patch
or adhesive (Fig. 9).
RECOMMENDATIONS FOR FASTENER REUSE:
1. Clean, unrusted prevailing torque nuts and bolts
may be reused as follows:
a. Clean dirt and other foreign material off nut
or bolt.
b. Inspect nut or bolt to insure there are no
cracks, elongation, or other signs of abuse
or overtightening. (If there is any doubt,
replace with a new prevailing torque
fastener of equal or greater strength.)
c. Lightly coat bolt & nut with engine oil.
Assemble parts and hand start nut or bolt.
d. Observe that before fastener seats, it
develops torque per the chart in Figure 10.
(If there is any doubt, replace with a new
prevailing torque fastener of equal or
greater strength.)
e. Tighten fastener to torque specified in
appropriate section of this manual.
2. Bolts and nuts which are rusty or damaged
should be replaced with new parts of equal or
greater strength.
VEHICLE LIFTING PROCEDURES
N O T I C E :
When jacking or lifting vehicle from
frame side rails, be certain lift pads do not contact
catalytic converter as damage to converter will
result.
Many dealer service facilities and service stations
are equipped with a type of automotive hoist which
must bear upon some part of the frame in order to lift
the vehicle. Figures 15 thru 17 indicate the
recommended areas for hoist contact.
If any other hoist methods are used, special care
must be used not to damage the fuel tank, filler neck,
exhaust system or underbody.