Piston codes

[bespander]

Need help deciphering piston codes.

82 & 83 have a alpha code and may have a color code. Alpha codes are large and small C's and D's. Color codes are blue (BL) and orange (OR).

88 has alpha code but no color code. Alpha code are all C's and D's but may have overbar, underbar, or both.

[lowstature]

The 6.2s are kind of a frankenstein engine. The pistons are not universal one size fits all.

The block is stamped next to the hole for each piston hole with a letter that must be matched to the piston. A with an A, B with a B, C with a C.... as far as upper case and lower case goes, I've not seen that. We build and rebuild 6.2's for the military where I work, so I see them every day.

Hope that helps.

I've seen engines with A,A,C,A,C,C and everywhere in between. Not sure how they figured that out at the Manufacture....

[Robyn]

Actually the 6.2 and the 6.5 are all select fit. Pistons and bearings are done this way.
The aftermarket offers standard and oversizes. Usually a standard aftermarket piston will fill the need on a STD bore.

The bearings were done in .0005 and .001 US/OS to allow for an absolute perfect fit.
I took a set of select fit shells out of my 94 6.5 and replaced them with STD clevite 77 when I did the rebuild.

Most of the new engines are all select fit. This allows the machining tollerances to be all over the map and the finished product will work fine.

Best
Robyn