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Pontiac Grand Prix Engine Information

The following technical bulletins were published by AERA.


                        Connecting Rod Oil Squirt Holes Eliminated On       
                                      Most 1973 GM Pontiac Engines 

The connecting rod oil squirt holes were eliminated in all GM Pontiac V-8 engines on September 18, 1972, starting with engine number 106178.  Some engines prior to this date and engine number had connecting rods both with and without squirt holes.  Replacement rods may be of either type and may be used interchangeably. 
                                                                                The AERA Technical Committee


                  Timing Gear Noise Or Knock On
            General Motors (Pontiac) 2.5L 1-4 Engines

The following information lists characteristics of timing gear
noise to assist diagnosis of problem cases involving the subject

Loose or improperly seated camshaft timing gears are usually
loudest when warm.  They are sensitive to speed only, not load
sensitive.  Cam gear noise will be noticed at a warm idle and
sounds much like a loose timing chain noise.  It is recommended
to remove the drive belts and use a sounding device on the timing
pointer.  This will provide a definite indication of timing gear

Timing gear noise is most noticeable at about 800 rpm.  It can be
heard the loudest at the timing gear cover and at the oil pan
between #3 and #4 cylinders.

If the noise has been diagnosed as timing gear related, Pontiac
Motor Division recommends AERA members use the following
procedure for checking timing gear backlash:

     1.  Remove the rocker arm cover and loosen all rocker arm
     retaining nuts on pre-1981 vehicles and shouldered bolts on
     1981 and later models.

     2.  Remove the timing gear cover.

     3.  Check the camshaft end clearance to determine if the
     gear is fully seated.  End clearance should be .0015 to

     4.  Using a magnetic dial indicator positioned on the front
     face of the engine block, place it on one tooth of the
     camshaft gear.  Be certain that the crank gear hub is

     5.  Rotate the camshaft gear back and forth.  Camshaft gear
     backlash should not be less than or exceed .0005 to .0095.

     6.  If the camshaft end clearance is over .005 or gear
     backlash exceeds .010 over the above limits, the timing
     gear and/or thrust plate should be replaced.

                                     The AERA Technical Committee

September 1983 - SB 105 



        Engine Miss & Exhaust Smoke At Highway Speeds On
 1982-83 General Motors (Pontiac) V-6 Diesel Engine (Vin Code T)

If you have a customer complaining about an engine miss followed
by a puff of blue smoke out the exhaust pipe, the problem may be
caused by engine oil leaking into the intake area of the cylinder

In such a case, AERA members may wish to advise their mechanic
customers to inspect the pipe-thread plugs that cover the upper
Torx(R) head bolts.  These may be a source of an oil leak if not
fully seated.

                                     The AERA Technical Committee

June 1983 - SB 102 



                                  Rocker Arm Installation Caution On
                                               Pontiac V-8 Engines

As indicated in the drawing, the nut which is used to secure the rocker arm to the rocker arm stud, has an internal taper which intersects an external taper on the rocker arm stud. Overtorquing of this nut will cause spreading and result in cracking the nut. A cracked nut will climb the external taper on the stud and
position the rocker arm too low for proper valve lifter function.

                                                                                 The AERA Technical Committee


                Caution On Cylinder Head Bolts On
             1982-83 GM (Pontiac) V6 Diesel Engines

The Torx(R) drive cylinder head bolt (part no. 22515533) is used
in 3 locations on each cylinder head in the subject engines and
is installed under the pipe plug as shown.  Some of these bolts
may have a washer face thickness of approximately 2.0mm (.080). 
If work is done on this engine that requires the removal of these
bolts, do NOT reuse them unless the washer face thickness is a
minimum of 2.8mm (.112).

Bolts that do not meet the minimum thickness should be discarded. 
Bolts with the thicker washer face are available under part no.

                      (insert illustration)

                                     The AERA Technical Committee

February 1983 - TB 270



                                                   Scuffing And Scoring

Distortion can result in scuffing and scoring.  Through the years emphasis has been placed on the importance of proper torquing of various bolts to avoid cylinder distortion which can reduce the piston operating clearance.  This includes the torquing of main bearing caps in place prior to boring cylinders so they remain round when the engine is assembled.  cylinders which are bored
without the main caps being installed and properly torqued are inclined to pull out of round (distort) when proper tension is put o the main bearing bolts in the final assembly.

Distortion of block bores is still of much concern with many late engines.  an example is the 1978 Pontiac 4.9L (301 CID) VIN  code Y and W.  Final bore operations were reportedly done in production using a deck plate.  The deck plate simulates the cylinder head in its installed position.  Thus, the boring and
finish operations are truer with less chance of the cylinders being distorted when assembled.  The use of deck plates had generally been a procedure used mainly by high performance.

Engine manuals list many torque specifications which are intended to reduce the distortion of various areas that could initiate a problem.  We strongly suggest that you follow the engine manufacturer's torque specifications and procedures.  This information shows the importance of the torque wrench.

                                                                         The AERA Technical Committee


                                      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


                                               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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