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MAIN BEARING KNOCK |
Main Bearing Knock On
GM 3.3 & 3.8L (Buick 3300 & 3800) Engines
AERA members report knocking noises coming from the front of GM 3300 & 3800 Buick engines. The noise is most noticeable when the engine has reached operating temperature. One possible cause for this knocking noise may be from excessive oil clearance at the front main bearing location.
Diagnosing excessive main bearing clearance is easily done by removing the accessory drive belt from the engine after it has reached operating temperature. If the noise diminishes when the engine is started again, front main bearing clearance may be more than .0012 (.030mm). The clearance may be reduced by installing .001 (.025 mm) undersize main bearings. GM permits the use of only one bearing shell half in the cap, but warns not to reduce
clearance below .0008 (.020 mm).
GM specifies the main bearing clearance as .0008-.0022 (.020- .055 mm). AERA suggests machining the crankshaft main bearing journals and the main bearing housing bore so that the minimum allowable clearance is maintained, avoiding the possibility of main bearing knock.
The AERA Technical Committee |
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PISTON KNOCK ON V6 ENGINES |
Piston Knock In
Some 1978 Buick Built V6 Engines
It has been reported that some Buick built V6 engines, which may be found also in vehicles of other GM divisions, may have a faint knocking noise particularly during warm up. The noise may be caused by the number 6 piston contacting the counterweight on the crankshaft.
A scuff mark on the skirt of the number 6 piston indicatesk the piston has been striking the crankshaft counterweight. To correct the problem, it is recommended that .010 be carefully filed or ground off the area of the scuffk mark.
The AERA Technical Committee |
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DETERMINING CORRECT CAMSHAFT - ODD & EVEN FIRE ENG |
Please Destroy Original TB 241 Dated Jan., 1982
Determining The Correct Camshaft On
1975-77 GM (Buick) Odd And Even Firing 3.8L (231 CID) Engines
Members are cautioned that there are two different types of
camshafts for the odd firing General Motors (Buick) 3.8L (231
CID) engine:
Type 1 has a non-integral distributor drive gear, a
removable drive gear on the end of the camshaft.
Type 2 has an integral distributor drive gear on the end of
the camshaft, permanently attached.
To identify an even or odd firing engine, check the V.I.N.
number. The fifth digit from the left denotes the type. A
letter C indicates an ODD firing engine. All other codes
indicate an even firing engine.
1975 through early 1977 General Motors (Buick) 3.8L (231 CID)
engines used odd firing. Later in 1977, even firing engines were
used.
The AERA Technical Committee
April 1982 - TB 241
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NEW CYLINDER LINER O-RINGS |
New Cylinder Liner O-Ring Seals On
Cummins NH/NT 6 Cylinder Engines
Cummins Engine Company has released new O-ring seals for the cylinder liners in NH/NT 6 cylinder engines. The new seals are made of an EP material and have a smaller diameter cross-section.
The new seal replaces both the old center seal #3008998 and the old lower seal #183049. The new seal carries Cummins part #3032874 and is black in color with one blue dot.
The new O-ring seals are not to be intermixed with the former seals on the same liner. Cylinder liner deformation will result. You can use the former seals and new seals in the same engine as long as they are used in the correct combinations on each liner. The illustration below shows the correct combinations.
The AERA Technical Committee |
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OIL IN COOLANT |
Oil in Cooling System on
VW 1.5L & 1.6L Diesel Engines
AERA members have reported instances of engine oil in the cooling system on VW 1.5L diesel engines. According to AERA sources, the problem is related to a crack in the cylinder head bolt hole located near the oil gallery feeding the cylinder head.
The oil feed gallery in the block is located on one side of the center head bolt hole and a coolant jacket is on the opposite side of the bolt hole. Pressurized engine oil is diverted through a slot in the head gasket and is feed up the side of the head bolt to the cylinder head. The oil also follows the bolt back down to the bottom of the bolt hole. Should the crack in the head bolt hole extend to the coolant jacket, oil can mix with engine coolant.
This problem is generally found on engines equipped with 11mm head bolt holes. Later design engines utilize 12mm head bolts and do not exhibit this defect. At the time of this writing no successful repair procedure is available.
The AERA Technical Committee |
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CYLINDER HEAD SPECS |
Cylinder Head Specifications on
Case 207 Diesel Engines
The following cylinder head specifications should be considered when remanufacturing Case Model 207 diesel engine cylinder heads.
The minimum cylinder head thickness has been established at 3.968 with a new head measuring 4.000 +/- .005. Heads are measured from the deck surface to the rocker cover rail.
Valve recession should be checked and adjusted if necessary to a maximum recession of .015, below the deck surface, for both intake and exhaust valves. Valves on new cylinder heads are generally flush with a +/- .005 tolerance.
The AERA Technical Committee |
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MAIN BEARING SADDLE REPAIR KITS |
Main Bearing Saddle Repair Kits
The Cummins Engine Company has made main bearing saddle repair kits available for several engines. These kits can be used to salvage cylinder blocks when a main bearing has spun and the main bearing saddle has been damaged.
Each kit contains an 1/8 drill bit, two hold down bolts (one for the lock ring and one for the other side of the saddle), a quantity of rivets and the appropriate number of repair sleeves. Semi-finished or good used main bearing caps are also needed to complete the repair.
A main bearing saddle can be successfully repaired by following this procedure.
Remove the main bearing cap from the saddle to be repaired. Using the appropriate align bore tooling remove .050 of material out of the saddle. This will enlarge the main bearing bore by .100.
Clean the saddle and lock tang area. Install the repair sleeve and align the lock tang slot of the sleeve with the one in the block.
From the repair kit, install the washer marked L on the lock tang side of the saddle. Install the second washer on the opposite side. Install the hold down screws and torque to 20 lbs.ft. (Figure 1).
Mount the 1/8 drill bit in a right angle drill, so that the drill extends 1/4 beyond the chuck jaws.
Using the 4 holes in the repair sleeve as a guide, drill through each of the holes into the saddle. The proper hole depth is achieved when the chuck jaws contact the repair sleeve.
Clean the 4 holes and install the supplied rivets (Figure 2). Peen the rivets until they are flush with the repair sleeve.
Remove the temporary hold down bolts and trim the ends of the repair sleeve so they are flush with the main bearing saddle.
Clean the main bearing bolt holes and install a good used or semi-finished main bearing cap. Torque the main bearing bolts to specifications.
Using the appropriate align boring tools, refinish the main bearing housing bore to specifications. Approximately .050 of material should be removed from the repair sleeve.
Main bearing bore repair kits or sleeves may also be available from several aftermarket sources.
The AERA Technical Committee |
