GM 6.5L V8 – Camshaft Features

The camshaft is made of forged steel and has sixteen lobes to operate hydraulic roller lifters for eight intake and eight exhaust valves (see Figure 2-10). A helical gear at the rear of the camshaft rotates the oil pump drive/engine speed sensor assembly. No machining of the camshaft journals or lobes is allowed during service.

During installation of the camshaft, all journals and lobes are coated with engine oil. The gear teeth that operate the oil pump drive/engine speed sensor assembly are coated with a special grease.

The camshaft has a driven sprocket mounted on its front end, using a key. A drive gear for the fuel injection pump also mounts on the front of the camshaft, and a bolt holds both the sprocket and the gear in place.

The timing chain between the crankshaft and camshaft is of the open roller, double-row design (see Figure 2-11). Timing is performed when the alignment mark of the camshaft sprocket is in the 6 o ’clock position, facing the crankshaft sprocket alignment mark.

For inspection during service, the timing chain has a procedure to check the maximum amount of deflection. A dial indicator is used to measure total travel as the chain is moved from its full outward to full inward position. The specification for timing chain deflection is 12.7 mm (0.500 in.) for a new chain and 20.3 mm (0.800 in.) for a used chain.

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