Just checked my GMH master parts catalogue which runs from '48 to HD.
No mention made of pistons in EJ being larger than standard 138.
However,
The oversize GMH pistons available went from .001 .002 .003 .020 .030 .040 thou.
I guess it wouldn't be much trouble for Holden to bore the 138 out to .040 thou oversize which ( without actually sitting down with the calculator and working it out ) would probably work out to around 143 cubes.
The .040 thou pistons ( if they are genuine GMH pistons ) would be stamped on the piston crown with part number 7406474.
I suppose its "possible" that at the near end of grey motor production that they may have looked at getting rid of surplus oversize pistons and fitted the .040 ones into the late run engines??
I suppose forum member Dr Terry might be able to answer that one
Interesting to see an optional GMH 4 ring piston for the grey available as well.
If you find a grey with these part numbers stamped into the piston crown you have a 4 ring piston set in it.
Standard Optional 4 ring type FB,EK,EJ Part Number M32518
.020 " " " " " " ' " " " M32520
.030 ' " " " " " " " " " M32521
.040 " " " " " " " " " " M32522
Also avaliable was a semi finished 4 ring piston " M32523
High Performance grey motor stuff here
