Usage:
All 3304 and 3306 Engines Made In The U.S.A.
- SUPPLEMENT: 08/06/79
SERVICE MAGAZINE, JULY 2, 1979, PAGE 6. In the chart that shows "FIRST USED SERIAL NUMBER" a 76R3474-up Serial Number is shown in the list for 3306 I & M Engines. This is not correct. The 76R3474-up Serial Numbers are for 3306 Truck Engines.
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Description of Change: Several improvements have been made to 3304 and 3306 Engines starting with the serial numbers shown in the chart.
... A new cylinder block uses a spacer plate instead of counterbores for the cylinder liners, and has a number of other changes to increase the strength of the block casting. The spacer plate design is similar to the design used on other Caterpillar engines.
... A new cylinder head is used with the new cylinder block. The new cylinder head has a different design of the oil passage to the valve mechanism. The supply of oil to the valve mechanism now flows through a hollow dowel, which has two O-ring seals to prevent leakage.
... New valve mechanism groups use new rocker shaft assemblies with a new bracket. The new bracket has a passage to permit oil flow from the hollow dowel to the rocker arm shaft. An O-ring seal is installed in the bracket to keep oil out of the area around the head bolt.
... Because the new cylinder block has no openings in the side, a new covers group has less covers, gaskets and bolts.
... Water seals are used with the new spacer plate. These seals are similar to those used on other spacer plate engines, but are orange in color for identification. (Some of the seals first used were gray).
... The crankshaft is not changed, but new thrust plates are used with the new cylinder block. The new thrust plates are thicker and have a tab (ear) to prevent wrong installation, which has caused damage to some engines. Since the cylinder block is machined for the thrust plate thickness and tabs, only the new thrust plates can be used with the new block. Thrust plates are available to permit installation of earlier, wide journal crankshafts in the new cylinder block. See the chart "Thrust Plate Application".
Adaptable To: All earlier engines when the necessary parts are used together, as shown in the parts chart. The new cylinder head is adaptable to the former cylinder block, but the former cylinder head is not adaptable to the new cylinder block.
