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TECHNICAL ADVICE - BRAND SPECIFIC

Compiled from comments and suggestions from a number of our clients and our own experience.

Mitsubishi 4D55/56

Camshaft Installation Tips and Trouble Shooting

1. Valve to piston problems - If the head has been decked, valve protrusion can result in valve to piston problems from approx. 3800 rpm up. The problems may not be apparent when turning the motor by hand or with a partially worn camshaft.
2. Similarly, if the engine has been rebuilt with replacement pistons or the block has been decked, valve to piston problems can occur as a result of piston protrusion.
3. The rocker shaft must be properly installed i.e. tightened down evenly with the two small oiling holes to the rear rocker pedestal.
4. The oilways in the rocker shaft and each rocker must be completely clear.
5. Fully check the rear rocker pedestal to ensure the oilways are clear and the pedestal is not cracked.
6. Ensure there is a good oil flow through the head to the rear rocker pedestal (note the insert in the head gasket has been known to move partially blocking the oil flow).
7. Oil and filter should be renewed. Before the rockers are fitted, crank the motor until the filter is full and oil is pumping to the rear rocker pedestal.
8. New or correctly reprofiled rockers must be fitted with the replacement camshaft however it has come to our attention that in some installations, wear or refacing of Mitsubishi 4D 55 rockers may cause the oil hole in the rocker shaft to be out of alignment with the oil hole in the rocker at the beginning of the lobe strike. This is not easy to detect. We are told that extending the hole where oil emerges from the rocker shaft slightly downwards will help solve this particular problem.
9. Use a quality MOLY PASTE (not grease) on the cam lobes and rockers before fire up.
10. Take the usual steps to avoid repeated cranking before initial start up and do not idle for the first hour of running.

NOTE: The above list should not be regarded as a comprehensive guide but merely highlights the areas which are known to have caused problems. We will be pleased to receive further comments and suggestions.