GENERAL INFORMATION y A Complete familiarity with the information on these gages as well as the general layout of the Parts Book will prove helpful in loca ing and ordering the desired parts The Book is arranged in sections as follows Model Series Information h A i Alphabetical Index A Chassis Parts Listing Groups 0 000 to 9 000 inclusive A Body Parts Listing Groups 16 000 to 17 999 inclusive Numerical Index V S The Grouping System for cataloging parts is used as followsg Main units of the vehicle are identified by a Numerical value preceding the Decimal i e A A Engine 0 Cooling and Oiling 1 1 Electr cal 2 Fuel System 3 Some Parts may be cataloged somewhere other than its original or prime group In such listings the pr1me group is indicated in paren hesis procedure s necessary since a part can have but one identifying Group Number for ordering or bin loca ion For examgle under Group Number 3 751 Par Number 7020926 is listed as Carburetor C oke Valve Screw and the pr1me group 3 820 is shown in the description column O READING TRUCK CATALOG FORMAT I The Truck Models included in this publication are listed as follows Conventional Models will be indicated with a M For further clarification see the Truck Series Identification Charts which follow the General Information Section of the catalog A 1985 91 TRUCKCATALOG FORMAT The 1985 91 truck catalog format is written in a similar way to that of the passenger car catalog us ng model codes in place body styles RPO Regular Pro duction Options wil also in most cases be called out in code w description where needed Refer to the RPO list for proper identification of RPO s WHEELBASE when the wheelbase dimension is essential to differentiate between models a 3 digit model number will be used For a full explanation on decoding the model code and wheelbase refer to the truck series identification chart 4 1 When using the dimensions and other data shown in the Description Column the Parts Manager should be guided by the following 1 length overall refers to the total length of a part measured over the longest dimension An irregular shaped piece is measured over the longest dimension regardless of contours and bends V A 2 dev length refers to the total length of a Bart such as a tail pipe on gas pipe measured as though the part were straig tened out This measurement can be taken on formed pipes by using a string to follow the contours of the pipe and then measuring the leng h of str ng used 3 I D refers to the inside diameter 0 D refers to the outside diameter 0 S refers to oversize U S refers to undersize V h ni t 1991 GENERAL MOTORS SERVICE PARTS OPERATIONS LTTRUCK 52M t A 4 1 91