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BALANCE SHAFT & CRANKSHAFT COMBINATIONS |
Balancer Assembly and Crankshaft Combinations On
GM 2.5L (VIN U) Engines
General Motors has provided the remanufacturing industry with another challenge when it comes to assembling GM 2.5L engines with balancer assemblies.
The balancer assembly first appeared in 1987 GM N body vehicles equipped with manual transmissions, such as the Pontiac Grand Am and Buick Somerset. This engine uses a crankshaft with the casting number 10044390. This crankshaft gear features 82 teeth while the driven balancer gears have 41 teeth.
Some OE parts books may list 625 as the casting number for the 1987 model year crankshaft. To-date AERA members have been unable to find crankshafts with this casting number.
Vehicles with VIN Code U engines may also use a crankshaft with the casting number 10044406. Unfortunately, there are two versions of this crankshaft. One version has a 78-tooth gear, which mates with 39 tooth balancer gears. The other version still uses 82 teeth and requires a 41-tooth balancer assembly.
Vehicles with VIN Code U engines manufactured for 1988 model year vehicles should only use casting number 1000406 crankshafts with 78 teeth.
Using the wrong combination of crankshaft and balancer assembly has caused complaints ranging from significant noise in the lower end of the engine, to premature engine failure. AERA members have reported 2.5L truck engines equipped with crankshafts that have a balancer drive gear although a balancer assembly is not used in this application.
For additional information see AERA Technical Bulletins: TB 778. 720, 690R & 511.
The AERA Technical Committee |
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LOW OIL PRESSURE ON 1987-90 'N' BODY ENGINES |
Low Oil Pressure On
1987-90 GM 2.5L (151 CID) N Body Engines
AERA members have reported low oil pressure conditions on 1988-90 GM 2.5L (151 CID) engines used in N body vehicles such as the Pontiac Grand Am and the Buick Somerset.
These engines are equipped with a combination balancer/oil pump assembly located in the crankcase to reduce high rpm engine imbalances. Furthermore, the oil filter cartridge is housed behind the filter access plug in the oil pan.
If the oil pan has been distorted by overtightening the filter access plug or drain plug it is possible for oil to leak back into the pan at the discharge side of the filter. This can results in extremely low or even no oil pressure.
This situation can be avoided through careful inspection of the oil pan area that houses the filter cartridge. Warped or otherwise damaged oil pans should be replaced.
For additional information see AERA Bulletin SB 157.
The AERA Technical Committee |
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CYLINDER HEAD IDENTIFICATION FOR 1985-87 2.5L ENG |
Cylinder Head Identification For
1985-87 General Motors 2.5L (151 CID) Engines
AERA members have reported confusion over replacing cylinder heads for 1985-87 2.5L (151 CID) engines even when using cylinder heads with the same casting number. The source for this confusion lies with General Motors using two differently machined configurations of a head carrying the same casting number for both the standard engine as well as the shortened version used in N body vehicles, such as the Pontiac Grand AM, Buick Somerset, etc. In 1985-86 this head carried the casting number 10027767. In 1987 it was replaced by casting number 10038808.
GM uses a shorter version of the 2.5L engine for the N body FWD cars, VIN code U, than for the cars that have VIN code R or 2. Although some components will interchange, the key pieces such as the block, head, crankshaft and camshaft will not. By measuring the center-to-center dimension of the rear holes of the cylinder head parallel to the flywheel, you can easily distinguish between the two applications. If the measurement is 3.670 it is the shortened version for the N body cars (VIN code U). If it is 3.980, it is the longer head for all other
vehicles (VIN codes R and 2). GM cast these bolt hole pads in an elliptical shape to allow for both versions.
The AERA Technical Committee |
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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 |
