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Where Should The Cam Bearing Oil Hole Be Located On A 3400 Series Cat Diesel?

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A:  The AERA Technical Committee offers the following information regarding cam bearing oil hole location for 3400 series Caterpillar diesel engines and installation of all cam bearings for these engines. This bulletin should be used, and service manuals published before 1985 should not be used.

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The correct location for the oil hole in the camshaft bearing is near the horizontal centerline of the bearing bore. This correct position is 75°-105° away from the oil hole in the block. Locating the bearing hole in this position will ensure that the oil hole is not located in the highly loaded area. The bearing joint should be located toward the top of the block.

The outside diameter of the camshaft bearing is grooved and directs oil from the cylinder block, around the camshaft bearing and out the hole in the bearing to lubricate the camshaft.

Q:  How critical are the heights of replacement combustion chambers on Kubota diesels?


A:  According to the AERA Technical Committee, the protrusion of these replacement combustion chambers above the deck of the cylinder head is critical. The correct specification is .001?-.004? (.025mm to .075mm) above the surface of the head. To adjust the height of these inserts, remove metal from the bottom side of the chamber. Removing metal from the top (the side with only notch opening) will make the insert more susceptible to cracking. Alternatively, you could remove the appropriate amount of metal from the insert counter bore.

Replacement combustion chambers are available for some Kubota diesel engines that were built from 1970 to 1999.

Q:  Is it OK to reuse the valve springs from a 1995 Mazda Protégé engine?

A:  The AERA Technical Committee offers the following information regarding valve spring breakage for 1995 Mazda 1.5L Z5 engines. Some 1995 Protégé engines may have inferior valve springs, prompting Mazda to issue recall notices.

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Valve spring breakage can cause engine chatter, damage to the engine pistons and cause engine failure.

Replace all springs when doing a valve job for this engine (if the history is not known).

When servicing these cylinder heads, both intake and exhaust valve springs (Mazda p/n Z50112125) should be replaced.

Q:  Are there any recommendations for priming an oil system after a rebuild?

A:  Reports of some premature engine failure on overhauled, new and/or remanufactured engines have been reported. These failures are often due to improper engine oiling system priming prior to engine startup, resulting in oil starvation to the engine at first start up.

The following information may help prevent any starvation problems after service work has been done on a Ford engine, but the procedures can be used for similar engines by other manufacturers:

Overhead Camshaft Engines

Ford OHC engines use a G-rotor pump design and are driven by the crankshaft. If the engine is rebuilt, the oil pump should be fed oil through the oil pick-up passage, prior to installing the pick-up tube and screen assembly. This can usually be accomplished by rotating the oil pump while oil is being fed into the oil pump inlet. Once the pump is primed with oil, it can be installed onto the engine.

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OHC engines, whether overhauled or remanufactured, prior to starting the engine, ensure that the engine crankcase is filled to specification with the correct engine oil (see AERA Technical Bulletin TB 1934). Disable the fuel supply to the fuel injectors and crank the engine over in 15-second increments until the oil pump is primed. An oil pressure gauge can be used to assist in determining when oil pressure is obtained.

Overhead Valve Engines

Ford OHV engines, commonly known as pushrod engines, use an oil pump driven by an intermediate shaft connected to the distributor, which is driven by the camshaft. In some instances there is a camshaft synchronizer assembly.

Whether the engine was overhauled or remanufactured or a replacement oil pump is installed, the oil pump should be primed prior to starting of the engine. In all these situations, ensure that the crankcase is filled to specification with the correct engine oil. Then, using an engine oil pump priming tool kit (available through aftermarket companies), rotate the oil pump unit until it is primed. The use of an oil pressure gauge will help in this process.

After a remanufactured engine is installed into the vehicle and the crankcase is verified to be full with the correct engine oil, disable the fuel supply to the fuel injectors and crank the engine over in 15-second increments, until the oil pump is primed. An oil pressure gauge can be used to assist in determining when oil pressure is obtained.

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Note For All Engines: Ensure that the inertia fuel shut-off switch is re-enabled prior to attempting to start the engine on both OHC and OHV engines. Regardless of the engine design, it is extremely important that the oil pump be correctly primed before the first engine start up.

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