found a t.s.b. on vg30e w seires changes and why they made the changes in the late 80's. i thought it was good info so here it is.
REVISED CYL HEAD & BLOCK ON 1987-UP ENGINES
Revised Cylinder Head & Block On
1987-Up Nissan 3.0L (VG30) Engines
Beginning with April, 1987 production, the cylinder heads and
block have been changed on Nissan 3.0L (VG30) engines.
Improvements were made to increase power output and decrease
noise levels of the engine.
Revised production engines can be identified by an engine serial
number that ends in W, such as XXXXXX W. Former engine serial
numbers end in either A or B. However, factory service
cylinder blocks will not carry the W identification even though
they feature the improvements listed below. A visual check is
necessary for proper identification.
Six new water galleries were added to the cylinder block (Figure
1) and the cylinder heads (Figure 2). This change required a
modification of the cylinder head gasket, where the original 6
water holes were downsized and 3 new holes added on the exhaust
side of the gasket (Figure 3). The revised cylinder head gasket
can also be identified by its differing identification tab.
Figure 4 best illustrates the former and revised head gaskets.
Additional changes were made throughout the engine. The pistons
now use full floating, larger diameter wrist pins. The small end
bore of the connecting rod was increased to accept the larger
wrist pin. The revised rod is also heavier than the former part.
Again, components are identified by a W stamp.
Nissan advises against the use of former parts when servicing
vehicles with engines manufactured as of April 1987. Refer to
the chart to determine the proper component combination when
servicing engines manufactured prior to April 1987 (Figure 5).
For additional information see AERA Technical Bulletins: TB 601,
653 & 752
The AERA Technical Committee
Cylinder Head Cylinder Short Acceptable
Head Gasket Block Block Combination
Revised Former Former N/A Yes
Former Former Revised N/A Yes
Former Former Former N/A Yes
Revised Revised Revised N/A Yes
Revised Former Revised N/A Yes
Revised Revised Former N/A No
Former Revised Revised N/A No
Former Revised Former N/A No
Former Former N/A Revised Yes
Revised Revised N/A Revised Yes
Revised Former N/A Revised Yes
Former Revised N/A Revised No
April 1991 - TB 761
Revised Crankshaft On
1984-87 Nissan VG30 Engines
Nissan has revised the snout of the crankshaft and related
service parts for VG30 engines manufactured after April 1987.
Since only the revised crankshaft is being serviced by Nissan,
should it become necessary to use this crankshaft in 1984-1987
engines, several associated parts also need to be changed.
Engines manufactured prior to April 1987 carry a serial number
that ends in either 'A' or 'B'.
Component Prior to As of
Description April 1987 April 1987
Crankshaft 12201-02P80 1 12201-02P81 2
Bolt Spacer Not Required 12308-V5321
Crank Pulley Bolt Washer 12308-V5000 3 12308-77A00
Crank Pulley Bolt 12309-V5000 12309-16V00
1 Does not include crankshaft pulley bolt washer or
crankshaft pulley bolt.
2 Includes crankshaft bolt spacer, crankshaft pulley bolt and
crankshaft pulley bolt washer.
3 Complete application information available on parts
The front pulley assembly is the same for either crankshaft.
The AERA Technical Committee
March 1991 - TB 752