GMC T Series 1994 Repair Manual page 10

1. ENGINE I. D. LOCATION
2. ENGINE I. D. LOCATION (OPTIONAL)
Important
• Most metric fasteners have a blue color coating.
However, this should not be used as positive
identification, as some fasteners are not color
coated.
General Motors Engineering Standards, along with
other North American Industries, has adopted a portion
of the standard metric fastener sizes defined by ISO
Figure 7—5.0L, 5.7L Engine I.D. Location
1. ENGINE I.D. LOCATION
2. ENGINE I.D. LOCATION (OPTIONAL)
Figure 8—7.4L Engine I.D. Location
(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.X1 screw which has
nearly the same diameter and has 25.4 threads per
inch. The thread pitch is in between the customary
coarse and fine thread pitches.
The difference is described in figure 20.
VIEW A
Metric and customary thread notation differ slightly.
V3246
V2592