Piston update

["Dan Curtis" <d.curtis@xxxxxxx>]

After doing quite a bit of research to see if I could find a picture of
pistons that looked like the ones in the freshly rebuilt balanced and
blueprinted engine that I bought a couple of years ago with the number 2381P
stamped on them, I discovered that the pistons look identical to 28cc valve
relief pistons for a 360 rather than the deep dish 401 pistons with an 8.5
compression ratio as was suggested on this list so I suspect these are also
28cc valve relief 401 pistons.  The single most significant difference was
that the valve relief on the pistons in my motor are completely within the
dish area rather than more toward the angled sides of dish that the 8.5
compression pistons have. Additionally, the pistons in my motor have a much
shallower dish depth than the low compression 8.5 compression 401 pistons
and in fact look like exactly like the 360 pistons rather than the 401 8.5
compression pistons.

I plan to determine the actual cc volume on these pistons before I put the
heads on but the bottom line is that although I was not able to find a
picture of the higher compression 401 pistons, and I have not yet been able
to determine if the 69 rods were replaced with 401 rods, it appears that I
have the higher compression 28cc valve relief 401 pistons rather than the
8.5s as was initially suggested on this list.  Based on the compression
spreadsheet that I have been using, it appears that I will end up with a
10.08:1 compression ratio in the 390 rather than the 8.9 that I originally
calculated this engine would have with 50.6cc heads.  Good news all around.

Best Regards,
Dan Curtis
Cell 602 317 2018
d.curtis@xxxxxxx