GM Full-Size Trucks 1970-1979 Repair Guide

Timing Gears



Inline 6-Cylinder Engines

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Timing gear alignment marks - inline 6-cylinder engine

The camshaft in these engines is gear-driven, unlike the chain-driven cams in V8s. The removal of the timing gear requires removal of the camshaft.

  1. After the cam is removed, place the camshaft and gear in an arbor press and remove the gear from the cam. Many well equipped machine shops have this piece of equipment if you need the gear pressed off.
  3. Installation is in the reverse order of removal. The clearance between the camshaft and the thrust plate should be 0.001-0.005" on both engines. If less than 0.0015" clearance exists, the spacer ring should be replaced. If more than 0.005" clearance, the thrust plate should be replaced.

The thrust plate must be positioned so that the Woodruff key in the shaft does not damage it when the shaft is pressed out of the gear. Support the hub of the gear or the gear will be seriously damaged. The 6-cylinder crankshaft gear may be removed with a gear puller while in place on the block.