VALVE AS 6D3943 - Caterpillar

All 3406B EnginesReference: SERVICE MAGAZINE, AUGUST 25, 1980, PAGE 10, the article "Special Bolts Available For Better Protection Against Modifications Of Fuel System And Governor Settings" gives information on tamperproof bolts for use on 3406 and 3408 Engines. Tamperproof bolts are available to prevent unauthorized modification of fuel system and governor settings on the above engines. These bolts are available only as parts service items; they are not installed at the factory as original equipment. Each of these bolts can be installed in place of one of the standard bolts as shown in Illustration 1. When the bolts are correctly installed, removal of the adjustment covers on the governor and fuel ratio control will be very difficult.
Use of all the bolts shown in Illustration 1 may not be necessary, depending on engine installation. It is important to remember that although the use of more tamperproof bolts offers a greater degree of protection, it also requires more labor to make approved fuel system repairs and adjustments.
Illustration 1. 7W6074 Governor Protection Fastener Group.The tamperproof bolts have two heads (see Illustration 2). The hex head, which is used to tighten the bolt, breaks off when the bolt is tightened to the correct torque [approximately 7 to 10 N m (5 to 7 lb ft)]. The second head is round.
Illustration 2. Typical tamperproof bolt.Tamperproof bolts are not serviced as a group. Order the individual bolts, as needed, from the chart.